14 hoa hoc huu co (phu).pdf

B CNG THNG

TRNG CAO NG CNG NGHIP TUY HA KHOA CNG NGH - MI TRNG

---[\---

TRN VN THM

Bi ging:

NH

N

N

O

NH2N

O

OH

HH

HHOH

OP-O

O

O-

Guanine

N

NN

N

NH2

O

OHOH

HH

HH

HO Adenine

N

NH2

ON

O

OHOH

HH

HH

OP-O

O-

OCytosine

NH

O

ON

O

OHOH

HH

HH

HOUracil

Tuy Ha, nm 2007

Organic Chemistry

http://hhud.tvu.edu.vn

Ho hc hu c - phn mc lc

http://www.ebook.edu.vn

Trang 1

PHN MC LC

Trang

Chng 1: I CNG V HO HC HU C

1.1. Hp cht hu c v ho hc hu c 4

1.2. Phng php tch v tinh ch cht hu c 6

1.3. Phn tch nguyn t v thit lp cng thc phn t 8

1.4. Lin kt trong ho hc hu c 10

Chng 2: CC HIN TNG NG PHN TRONG HA HU C 16

2.1. ng phn cu to 16

2.2. ng phn lp th 17

Chng 3: S TC DNG TNG H CC NGUYN T TRONG PHN T 24

3.1. Hiu ng cm ng 24

3.2. Hiu ng lin hp 26

3.3. Hiu ng siu lin hp

3.4. Hiu ng khng gian

29

30

Chng 4: PHN NG HU C 32

4.1. Mt s khi nim chung 32

4.2. c im ca phn ng hu c 32

4.3. Phn ng th trong ho hc hu c 34

4.4. Phn ng tch loi trong ho hc hu c 36

4.5. Phn ng cng hp trong ho hc hu c 39

Chng 5: HIROCACBON 42

5.1. Hirocacbon no 42




Trang 2

5.2. Hirocacbon khng no 50

5.3. Hirocacbon thm 67

Chng 6: HP CHT HU C N CHC V A CHC 77

6.1. Dn xut halogen 77

6.2. Hp cht c nguyn t 85

6.3. Ancol v phenol 90

6.4. Anehit v xeton (hp cht cacbonyl) 102

6.5. Axit cacboxylic v dn xut 110

6.6. Amin 124

Chng 7: HP CHT TP CHC 130

7.1. Hiroxiaxit 130

7.2. Gluxit 131

7.3. Aminoaxit 140

7.4. Protein 141

Chng 8: HP CHT D VNG 145

8.1. Khi nim 145

8.2. D vng 5 cnh mt d t 147

8.3. D vng 6 cnh mt d t - Piriin 149

THC HNH 152

Bi 1- Phn tch nguyn t trong HCHC 152

Bi 2- Hiro cacbon 154

Bi 3- Dn xut halogen ca hirocacbon 161




Trang 3

Bi 4- Ancol phenol ete 165

Bi 5- Anehit xeton 170

Bi 6- Axit cacboxylic v dn xut 175


Chng 1: i cng v ho hc hu c http://www.ebook.edu.vn Trang 4

Chng 1: I CNG V HO HC HU C

1.1. Hp cht hu c v ho hc hu c

1.1.1. Khi nim v hp cht hu c v ho hc hu c

Cacbon l mt nguyn t ho hc rt c bit: cc nguyn t C c th kt hp vi nhau v

vi nguyn t ca nguyn t khc to nn khong 10 triu hp cht khc nhau, y l nhng hp

cht ca cacbon. Trong khi , cc nguyn t ho hc cn li trong BTH ch c th to nn chng 1

triu hp cht khng cha cacbon.

Nhng hp cht ca C (tr CO, CO2, cc mui cacbonat, ...) c gi l hp cht hu c.

Ngnh ho hc chuyn nghin cu cc hp cht hu c, tc l cc hp cht cha cacbon,

c gi l ngnh ho hc hu c.

1.1.2. Lc s pht trin ngnh ho hc hu c

Loi ngi bit iu ch v s dng cc sn phm hu c dng khng tinh khit hoc

hn hp t rt lu (ng ma, gim, phm nhum, tinh du, ...), song mi ti gia th k XVIII

mi tch c t thc vt v ng vt mt s hp cht hu c tng i tinh khit (axit citric, axit

tactric, ure, ...)

u th k XIX ho hc hu c tch ra t ho hc ni chung, v tr thnh mt ngnh khoa

hc c lp. Ngi ta gi ho hc hu c (Beczeliuyt, 1806) v hi ch c cc cht hu c thin

nhin tn ti trong c th ng vt v thc vt. V th, thi by gi xut hin mt quan nim duy

tm gi l thuyt lc sng, theo cc cht hu c ch c th sinh ra trong c th sng nh mt

lc huyn b no . Quan nim ny ch tn ti c vi chc nm, v b bc b bi cng trnh

tng hp hng lot hp cht hu c xut pht t cc cht hu c khc hoc cc cht v c, nh

tng hp axit oxalic (1824), ure (1828), cht bo (1854), .... Cng vi nhng thnh tu v tng hp

hu c, t gia th k XIX hnh thnh thuyt cu to ho hc (1861) v quan nim u tin v

ho hc lp th (1874).

Bc sang th k XX, trong ho hc hu c hnh thnh thuyt electron v cu trc phn

t v khi u thi k pht trin mnh m cng nghip hu c (nhin liu, dc phm, phm

nhum, polime, ...).

Sau chin tranh th gii th hai, cng vi s pht trin v bo ca ho hc lp th, cc

thuyt electron v cu trc phn t v c ch phn ng. S thm nhp ca ton hc, c hc, vt l

hc, ... vo ho hc hu c v s thm nhp su mnh ca ho hc hu c vo cc ngnh sinh

hc, y dc, nng nghip, ... v c bit l s pht trin cc phng php vt l nghin cu cht

hu c cng vi cc php phn tch v tng hp hu c hin i.

Hin nay hoa shc hu c ang thi k pht trin mnh m nht v c vai tr quan trng

trong mi ngnh kinh t quc dn. Cc cht hu c c mt khp ni, ngoi c th sng ta gp cht

hu c trong thc phm, dc phm, phm nhum, cht do, si t, cao su, m phm, bt git,

cht phng tr dch hi, cht kch thch tng trng, thuc n, nhin liu, .... Trong th gii quanh

ta, u u cng c bng dng hp cht hu c.



Nh c ho hc hu c ngi ta mi hiu c su sc cc cht to nn c th sng v

bn cht qui trnh din ra trong c th sng. V vy, ho hc hu c l c s ca cc ngnh ho

hc trung gian nh ho sinh, ho dc, .... Ho hc hu c khng cn l mn hc m t thun tu

nh trc y, m t lu tr thnh mt mn hc suy lun, va c l thuyt va c thc

nghim.

1.1.3. Phn loi hp cht hu c

C th phn loi hp cht hu c theo hai cch chnh sau y:

a) Phn loi thnh H C v dn xut ca H C

H C l nhng hp cht hu c c cu to bi hai nguyn t H v C.

Cc dn xut ca H C cha trong phn t khng nhng C v H m cn c c nhng

nguyn t khc nh O, N, S, .... l nhng hchc c nhm chc.

Nhm chc l nhm nguyn t (or: nguyn t) quyt nh tnh cht ho hc c trng ca

c dy hp cht c cng loi nhm chc trong phn t (gi l chc ho hc).

Khi phn t ch c mt nhm chc duy nht ta gi l hp cht hu c n chc. Th d:

C2H5OH, CH3CHO, CH3COOH, ...

Khi phn t c hai hay nhiu nhm chc ng nht ta gi l hp cht hu c a chc. Th

d: (COOH)2, CH2OH CHOH CH2OH, ...

Khi phn t c hai hay nhiu nhm chc khc ta gi l hp cht hu c tp chc chc. Th

d: NH2CH2-COOH, CH2OH (CHOH)4 CHO, ...

b) Phn loi theo mch C

H C v dn xut ca chng u c th c phn loi theo mch C (mch h, mch

vng, mch no, mch khng no, ...)

Cc hp cht hu c

Hp cht mch h (hp cht khng vng)

Hp cht mch vng (hp cht vng)

Hp cht no (mch C ch c LK n)

Hp cht khng no(mch C c LK bi)

Hp cht ng vng(trong vng ch c C)

Hp cht d vng (Trong vng ngoi C cn c O, N, S, ...)

Vng no

Vng khng noVng thm

D vng no

D vng khng no

D vng thm



1.1.4. Ngun hp cht hu c

Trong thin nhin: c nhiu ngun hp cht hu c rt phong ph. l, du m v kh

thin nhin (ch yu l cc H C), than (cung cp nha than cha H C thm, phenol, ...),

cc sn phm ng - thc vt (cung cp gluxit, lipit, protein, ...)

Trong phng th nghim v trong cng nghip: ngi ta c th tng hp hng triu hp

cht hu c khc nhau, xut pht t cc cht hu c v v c, trong c nhiu sn phm cng

nghip c ssn xut trn c s cc ngun nguyn liu thin nhin nu trn.

1.2. Phng php tch v tinh ch cht hu c

Hu ht cc cht trong thin nhin hay mi iu ch trong phng th nghim u trng

thi hn hp vi thnh phn khc nhau. kho st cu trc v tnh cht ca mt cht hu c

bng thc nghim v s dng trong thc tin ngi ta phi tch cht ra khi hn hp, nhm

tinh ch n thnh mt cht tinh khit hay cht nguyn cht.

1.2.1. Cc phng php thng thng

a) Chit

Ngi ta dng mt dung mi thch hp (nh ete, benzen, nc, ...) c kh nng ho tan tt

cht hu c cn tch t mt hn hp lng hoc rn vi cht khc sang dung dch trong dung mi

. Sau khi ui dung mi ra khi dung dch ta s thu c cht cn tch.

Th d: khi iu ch C6H5NH2 bng phng php kh C6H5NO2 c mt phn nh anilin tan trong nc. tch anilin ra khi nc, ngi ta cho ete vo v lc k, anilin d tan trong ete hn nc s chuyn sang ete. Tch anilin/ete ra

khi v dui ete i ta s thu c anilin.

Hin nay c rt nhng dng c cho php chit lin tc.

b) Kt tinh

Phng php ny da vo s khc nhau v tan ca cc cht (ch yu l cc cht rn)

trong dung mi thch hp, v s khc nhau v tan ca mt cht trong mt dung mi nhit

khc nhau.

Ngi ta ho tan mt hn hp rn trong mt dung mi thch hp bng cch un nng v

lc, sau lc nng loi b tp cht khng tan ri lm lnh. Khi y cht t tan hn s tch ra

trc dng tinh th sch v c ly ra bng cch lc.

Th d: axit benzoic l cht rn tan nhiu trong nc nng v rt t tan trong nc ngui. tinh ch ngi ta un axit ny trong nc c dung dch bo ho nng, ddem lc nng, ri ngui cc tinh th axit tinh khit hn s tch ra.

c) Chng ct

Phng php ny da trn s khc nhau v nhit si ca cc cht khc nhau mt p

sut nht nh. Ngi ta dng nhit (un nng) chuyn hn hp cht lng sang pha hi v thu

cht lng khong nhit thch hp bng cch cho hi ngng t. C ba kiu chng ct thng

dng:

Chng ct thng: Khi tch mt cht lng c nhit si khng cao ra khi cc cht khc c nhit si khc xa ta c th chng ct bng cch on gin nht gi l chng ct



thng. Th d, un si nc sinh hot trong bnh, nc s bc thnh hi, dn hi qua b phn

lm lnh hi nc ngng t thnh nc tinh khit hn, cn li trong bnh l cc cht kh bay

hi.

Chng ct phn on: Phng php ny dng tch hn hp lng gm cc cht c nhit si cch xa nhau khng nhiu lm, nh mt dng c gi l ct ct phn on gn lin hoc lp

thm vo bnh cng ct. Cht no c nhit si thp hn s bay hi trc ri ngng t ri ly

ring ra, tip theo n cht no c nhit si cao hn. Th d, hn hp gm benzen v toluen

trong bnh c lp ct ct phn on, benzen s bay hi v thot ra trc, sau n toluen.

i vi cht c nhit si cao v d phn hu nhit si ca n, ngi ta chng ct

di p sut thp h nhit si v trnh s phn hu.

Chng ct bng cch cho li cun theo hi nc: C nhng cht hu c nhit si rt cao v rt t tan trong nc, song c th c chng ct dng hn hp vi hi nc

nhit si ca nc.

Cch tin hnh: cho mt dng hi nc nng i qua hn hp cc cht cn tch ra, hi nc s lm cho mt vi thnh phn ca hn hp bay hi theo hi nc. Th d, chng ct anilin, tinh du thc vt, ...

1.2.2. Phng php sc k

Nguyn tc: hn hp cc cht cn tch v dung mi c dng lm pha ng th lng

hoc kh. Pha ng thng xuyn tip xc vi pha tnh l mt cht rn c din tch b mt rt ln,

hoc mt cht lng trng ln b mt cht rn, khin cho cc thnh phn ca hn hp c tc

chuyn dch khc nhau s tch ra khi nhau.

Phn loi: ta phn bit hai loi chnh l sc k hp ph v sc k phn b.

a) Sc k hp ph

Da theo s khc nhau v h s hp ph ca cc cht. Pha tnh l mt cht rn, pha ng

l cht lng hoc cht kh. Sc k hp ph c th c cc dng sc k ct, sc k lp mng, sc k

kh.

b) Sc k phn b

Pha tnh l cht lng, pha ng l cht lng hoc cht kh. Sc k phn b c th l sc k

ct, sc k lp mng, sc k kh.

Sc k ct: thng gp l loi m pha tnh l cht rn nh alumin (Al2O3), silicagen

(SIO2.nH2O) c t trong mt ng thng ng (ct), pha ng l dung dch cha hn hp cn

tch trong dung mi thch hp.

Sc k giy: thng pha tnh l nc ng v trn giy.

Sc k lp mng: pha tnh l lp mng cht hp ph nh silicagen trng trn mt bn thu

tinh hoc bng nhm, pha ng l dung dch cha hn hp cn tch c a vo bng cch

nhng hoc nh git, cht lng di chuyn nh tc dng mao dn.

Sc k kh: Pha ng l mt cht kh, cn pha tnh c th l cht rn hoc cht lng.



1.3. Phn tch nguyn t v thit lp cng thc phn t

1.3.1. Phn tch nh tnh nguyn t

Phn tch nh tnh nguyn t nhm xc nh cc loi nguyn t c mt trong hp cht hu c.

Nguyn tc chung l chuyn cc nguyn t trong hp cht cn kho st thnh nhng cht

v c n gin ri nhn ra cc sn phm ny da vo nhng tnh cht c trng ca chng.

a) Xc nh C v H

un nng cht hu c vi CuO (cht oxy ha) chuyn C thnh CO2 v H thnh H2O, ri

nhn bit CO2 bng nc vi trong (to kt ta trng CaCO3) v nhn bit H2O bng CuSO4 khan

(mu trng chuyn thnh mu xanh ca CuSO4.5H2O)

[C]hchc + 2CuO CO2 + 2Cu [H]hchc + CuO H2O + Cu CO2 + Ca(OH)2 CaCO3 + H2O 5H2O + CuSO4 CuSO4.5H2O b) Xc nh N

un nng hp cht hu c vi Na s xinh ra NaCN. nhn ra ion CN- ta cho thm Fe2+

v Fe3+ ri axit ho nh, nu c CN- s sinh ra kt ta mu xanh m rt c trng ca

Fe4[Fe(CN)6]3:

Na + [C] + [N] NaCN hp cht hu c

Fe2+ + 6CN- [Fe(CN)6]4- 4Fe3+ + 3[Fe(CN)6]4- Fe4[Fe(CN)6]3 c) Xc nh halogen

t mt bng giy lc tm cht hu c c cha Hal v ancol etylic (nhin liu) s sinh ra

HX. Ta nhn bit HX bng dd AgNO3 (sinh ra kt ta AgX) sau xc nhn AgX bng dd NH3 (ho

tan kt ta):

[X]hchc + [H]hchc or ancol HX HX + AgNO3 AgX + HNO3 AgX + 3NH3 + H2O [Ag(NH3)2]OHtan + NH4X 1.3.2. Phn tch nh lng nguyn t

Phn tch nh lng nhm xc nh thnh phn % v khi lng ca cc nguyn t trong

hp cht hu c. Nguyn tc chung l chuyn hon ton cc nguyn t trong mt lng cn nht

nh ca cht hu c thnh cc cht v c n gin, sau xc nh khi lng (hoc th tch i



vi cht kh) c sn phm , ri tnh thnh phn % cc nguyn t.

a) nh khi lng C v H

Nung nng mt lng cn chnh xc a gam hp cht hu c vi CuO d trong dng kh

O2. Kh CO2 v hi nc sinh ra c hp th hon ton v ring r bi nhng bnh cha cc cht

hp th thch hp c cn trc v sau khi th nghim. Gi s trong th nghim sinh ra 2CO

m v

OHm 2 , ta tnh:

44

122CO

C

mm

= 18

22OH

H

mm

=

10044

12% 2

=a

mC CO 100

182

% 2 =

am

H CO

b) nh lng N

un nng mt lng cn chnh xc a gam hp cht hu c vi CuO d trong dng kh

CO2 chuyn ht N trong hp cht thnh kh N2 v dn vo nit k (dng c o kh nit) cha

trong dd KOH m c ( hp th CO2 v H2O). Gi s thu c V ml kh N2, o nhit t, p

sut kh quyn p, p sut hi nc bo ho f, ta tnh c :

2731

176022400

282 t

fpVmN +=

100% 2 =am

N N

c) nh lng halogen

Sau khi phn hu mu cht hu c chng hn bng oxi hay axit nitric bc khi, cc

halogen c chuyn thnh AgX nh lng.

d) nh lng oxi

Thng thng hm lng oxi trong mt hp cht hu c c xc nh trc tip bng

cch ly 100% tr i tng s % ca cc nguyn t khc c trong hp cht. tuy vy, khi cn thit

cng c th xc nh trc tip bng cch chuyn oxi trong mu thnh CO ri nh lng CO da

theo phn ng:

5CO + I2O5 5CO2 + I2 1.3.3. Xc nh phn t khi

i vi cc cht kh hoc cht lng d bay, ta c th xc nh t khi d ca cht so vi

mt kh n gin no (th d: H2, N2, khng kh, ...) ri tnh khi lng phn t:

B

A

BA M

Md =



i vi cht rn hoc cht lng khng bay hi: da vo phng php nghim lnh v

phng php nghim si:

tg

gkM =2

1 1000

Php nghim lnh c dng rng ri hn php nghim si.

1.3.4. Thit lp cng thc phn t

Gi s hp cht hu c c CTPT l CxHyOzNt

Lp cng thc n gin nht: x : y : z : t = 14

:16

:1

:12

NOHC mmmm

Lp cng thc phn t da vo khi lng cc nguyn t:

aM

mt

mz

my

mx

NOHC

==== 141612

Lp cng thc phn t da vo phn trm cc nguyn t:

100%

14%16

%%12 M

Nt

Oz

Hy

Cx ====

Th d: t chy hon ton 0,44 gam mt hp cht hu c A, sn phm chy c hp thu hon ton vo bnh 1 ng P2O5, v bnh 2 ng dung dch KOH. Sau th nghim thy khi

lng bnh 1 tng 0,36g v bnh 2 tng 0,88.

a) Xc nh CTn gin nht ca A?

b) Xc nh CTCT ng ca A, bit phn ng ht vi 0,05 mol A cn dng 250ml dung

dch NaOH 0,2M v A c kh nng tham gia phn ng trng gng.

1.4. Lin kt trong ho hc hu c

1.4.1. Lin kt xch ma () v lin kt pi () Lin kt ho hc quan trng v ph bin nht trong hp cht hu c l lin kt cng ho

tr. Lin kt ny c hnh thnh bng s xen ph cc obitan nguyn t (AO) to nn obitan phn

t (MO) chung cho c hai nguyn t tham gia lin kt. C hai kiu xen ph chnh:

a) Xen ph trc

MO c trc i xng trng vi trc ni hai ht nhn nguyn t lin kt:

s - s (xichma) p - p (xichma) s - p (xichma)

Hnh 1.1: Obitan l nhng MO bn vng, c gi l MO . Lin kt cng ho tr c hnh thnh bng s xen ph trc nh trn c gi l lin kt xch ma.

Lin kt tng i bn, hai nguyn t ni vi nhau ch bng lin kt thi th c kh



nng quay quanh trc lin kt m khng lm mt s xun ph (th d: CH3 CH3), do c kh

nng xut hin cu dng hp cht hu c.

b) Xen ph bn

Vng xen ph nm hai bn tc ni hai ht nhn nguyn t lin kt nn MO tng i

km bn. l MO , v lin kt tng ng l lin kt . So vi lin kt xch ma th lin kt pi km bn.

Hai nguyn t ni vi nhau bng lin kt pi (v mt lin kt xch ma) khng th quay quanh

trc ni hai ht nhn c v nh th s vi phm s xen ph cc i ca hai AO. Do , c kh

nng xut hin ng phn hnh hc cc hp cht c ni i: C = C, C = N, ...

p - p

Hnh 1.2: Obitan pi

1.4.2. S lai ho obitan v cc lin kt n, i, ba

trng thi c bn nguyn t C c cu hnh electron: 1122 2221 yx ppss

trng thi lin kt nng lng cao, mt electron 2s chuyn ch sang obitan cn trng

2pz, do C* c cu hnh: 11112 22221 zyx pppss

Khi y c s t hp gia obitan 2s vi mt s obitan 2p, gi l s lai ho obitan. Cc

obitan mi hnh thnh c gi l obitan lai ho. Cacbon c 3 kiu lai ho:

a) Lai ho sp3 (hay lai ho t din)

Lai hoa sp3: Mot obitan 2s lai hoa vi 3 obitan 2p tao thanh 4 obitan lai hoa sp3 giong het nhau. Bon obitan nay hng ti 4 nh cua hnh t dien mat eu, tao thanh goc gia cac obitan lai

hoa la 109028/ (hnh 1.3)

sp3+

-

+

-+

+

--

109o28/+

+

+-

--

Hnh 1.3: S lai hoa sp3

Cac obitan sp3 se xen phu truc vi AO cua cac nguyen t khac tao thanh nhng lien ket .



Th du:

CH4

C2H6

Hnh 1.4: Cc obitan trong phn t CH4 v C2H6 b) Lai ho sp2 (hay lai ho tam gic)

Lai hoa sp2: Mot obitan 2s lai hoa vi 2 obitan 2p tao thanh 3 obitan lai hoa sp2 giong het

nhau. Ba obitan nay hng ti 3 nh cua tam giac eu, hnh thanh goc gia cac obitan lai hoa bang

1200 (hnh 1.5).

120o+

-+

-

+

+

-+

+

+

-

-sp2

Hnh 1.5: S lai ho sp2

Cc obitan sp2 s xen ph trc vi obitan ca cc nguyn t khc to thnh cc lin kt

xch ma. Cn li mt obitan 2p cha lai ho c trc thng gc vi mt phng cha 3 obitan lai ho

sp2 s dng xen ph bn vi obitan 2p ca nguyn t khc to thnh lin kt pi (th d hnh 1.6).

(a) (b)

HH

H H

Hnh 1.6: S hnh thnh lin kt xch ma (a) v lin kt pi (b) trong phn t C2H4

c) Lai ho sp (hay lai ho ng thng)

Lai hoa sp: Mot obitan 2s lai hoa vi 1 obitan 2p tao thanh 2 obitan lai hoa sp giong het

nhau. Hai obitan nay nam tren mot ng thang tao thanh goc gia hai obitan lai hoa bang 1800



(hnh 1.7).

180O

sp2s

2p

sp

Hnh 1.7: S lai ho sp

Cc obitan sp s xen ph trc vi obitan ca hai nguyn t khc to thnh hai lin kt xch

ma. Cn li hai obitan cha lai ho 2p c trc i xng thng gc vi nhau v cng thng gc vi

trc i xng chung ca hai obitan lai ho sp, s dng xen ph bn vi obitan cha lai ho ca

nguyn t khc to nn nhng lin kt pi.

Th d:

180o180o

H HH C C H

a) b)

Hnh 1.8: S hnh thnh lin kt xch ma (a) v lin kt p (b) ca C2H2

1.4.3. Lin kt hiro

a) Khi nim

Lin kt hiro l lin kt c hnh thnh gia mt nguyn t H tham gia lin kt cng

ho tr vi mt nguyn t khc cng d tham gia lin kt cng ho tr v cn cha cp electron t

do.

Th d: lin kt hiro c hnh thnh gia phn t H2O

H O ... H O ... H O ... H O

H HHH

iu kin hnh thnh lin kt hiro: l LKCHT X H cha nguyn t H phi phn cc

mnh, nguyn t H mang mt phn mang in tch dng (+), cn nguyn t th hai Y phi c cp e t do mang mt phn in tch m (-) v c m in ln hn.

X

+H

Y

y X cng nh Y thng l O, N, F. Lin kt X H cng phn cc v kh nng nhng

electron ca Y cng ln th lin kt hiro cng bn vng.

b) Phn loi lin kt hiro

Lin kt hiro lin phn t: l lin kt gia X H v Y thuc v hai phn t ring r

(ging nhau hoc khc nhau). Th d:

LKCHT phn cc

Lin kt hiro



H O ... H O

C2H5 CH3C6H5C2H5

H O ... H O CH3 C C CH3O H ... O

O ... H O

Lin kt hiro ni phn t: l lin kt gia X H v Y ca mt phn t. Th d:

CH2 O

CH2 OH

H

F

O H

c) S nh hng ca lin kt hiro n tnh cht ca hp cht hu c

Lin kt hiro lin phn t lm tng mnh nhit si v nhit nng chy so vi nhng

cht c phn t khi tng ng m khng c lin kt hiro hoc ch c lin kt hiro ni phn t.

Th d:

Hp cht M ts (oC) tnc (oC)

CH3 CH2 OH 46 78 -

CH3 O CH3 46 -24 -

CH3 SH 48 6 -

p-NO2 C6H4 OH 139 - 114

o-NO2 C6H4 OH 139 - 44

S hnh thnh lin kt hiro gia cht tan v dung mi lm tng mnh tan trong dung

mi . Nhm chc c kh nng to lin kt hiro vi dung mi cng tng th tan ca cht cng

ln, tri li gc H C cng ln tan ca cht cng nh. Th d:

Hp cht M tan (g/100g H2O)

CH3 CH2 OH 46 N C4H9 OH 74 7,4

n C6H13 OH 102 0,6

C6H12O6 (glucoz) 180 83

n C6H14 86 0,01

CH3 COOH 60 HCOOCH3 60 30

Ch rng ngoi lin kt hiro ra, gia cc phn t hp cht hu c cn c th c cc lc

lin kt yu nh lc ht lng cc gi cc phn t phn cc, lc Vandecvan, ...



BI TP

1.1. Hy nu nh ngha: cht hu c, ho hc hu c, H C, gc H C, gc t do, dn xut ca

hirocacbon.

1.2. Cho cc cng thc sau y: CH3Cl (A); COCl2 (B); CaC2 (C); C2H6 (D); C6H6 (E); CH3COOH

(F); CH3 C+H CH3 (G); H2C2O4 (H); CH3 CH2*(I). Hy ch r hchc, H C, nhm chc?

1.3. Nguyn tc chung ca php phn tch ho hc cc nguyn t trong hchc l g? Minh ho bng

hai th d c th ?

1.4. Adrenalin l mt hocmon. Trn 18,3 mg adrenalin vi bt CuO (ly d) ri nung nng th thu

c 1,27 ml kh nit (o 270C v 750 mmHg). Nu t chy hon ton cng adrenalin

lng trn nh vy trong oxi th thu c 39,6 mg CO2 v 11,7 mg H2O. Tm thnh phn %

cc nguyn t trong adrenalin ?

1.5. C mt cht hu c khn gtinh khit ly t ngun thin nhin. Hy nu cc bc thc nghim

v tnh ton thit lp CTPT ca hp cht ?

1.6. Phn tch nh lng 10,5 mg hp cht hu c A (cha C, H, O) thu c 30,8 mg CO2 v 4,5

mg H2O. Ho tan 1,03g A trong 50 gam benzen ri xc nh nhit si ca dung dch thy

ts=80,3560C, trong khi benzen nguyn cht c ts = 80,10C. xc nh CTPT ca A, bit hng s

nghim si trong trng hp ny l 2,61.

1.7. Hy nu nguyn tc ca mt vi phng php tinh ch hchc: cht rn v cht lng?

1.8. Hp cht hu c A c khi lng phn t nh hn khi lng phn t ca benzen ch cha 4

nguyn t C, H, O, N, trong hiro 9,09% nit 18,18% t chy 7,7 gam cht A thu c

4,928 lt kh CO2 o 27,30C, 1atm v A tc dng vi dung dch NaOH. Cho bit cng thc

cu to c th c ca A?

1.9. Cht X cha cc nguyn t C, H, O trong hiro chim 2,439% v khi lng. Khi t chy X

u thu c s mol nc bng s mol mi cht chy, bit 1 mol X phn ng va ht vi

2,0 mol Ag2O trong dung dch amoniac. Xc nh cng thc cu to ca X?

1.10. t chy hon ta 4,5 gam cht hu c A (gm C, H, O) thu c 3,36 lt CO2 (ktc) v

2,7 gam H2O. T khi ca Z so vi H2 bng 30.

a) Xc nh CTPT ca cht A?

b) A c ng phn th nht l X tc dng vi Na2CO3 gii phng CO2, ng phn th hai l

Y tc dng vi dd NaOH to ra ru metylic v ng phn th 3 l Z va tc dng vi Na v va

c phn ng trng gng. Xc nh CTCT ca X, Y v Z.

1.11. Bn cht ca lin kt CHT l g? Hy trnh by bng hnh v theo quan nim hin i s

hnh thnh cc lin kt cng ho tr trong mi phn t sau y:

CH3 CH3 ; CH2 = CH2 ; CH CH ; CH2 = CH CH = CH2 v C6H6 1.12. Bn cht ca lin kt hiro l g? Nu th d minh ho. Trnh by bng CTCT lin kt hiro

gia cc phn t trong trng hp: metanol, axit axetic, dd phenol trong etanol.


Chng 2: Cc hin tng ng phn trong ha hu c http://www.ebook.edu.vn

Trang 16

Chng 2: CC HIN TNG NG PHN TRONG HA HU C

Cc hin tng ng phn gn lin vi cu to v cu trc khng gian ca phn t. y l

mt hin tng rt ph bin trong ha hc hu c. Nh c hin tng ng phn ny m s cc

hp cht hu c tng ln rt nhiu.

Cc cht gi l ng phn vi nhau l nhng cht c cng cng thc nguyn, nhng khc

nhau v CTCT v tnh cht.

Ngy nay ngi ta bit rt nhiu hin tng ng phn. phn bit v s dng c th

chia ra lm hai dng biu din:

ng phn cu to (ng phn mt phng)

ng phn lp th (ng phn cu trc)

2.1. ng phn cu to

2.1.1. ng phn v mch cacbon

ng phn v mch C l ng phn v cch sp xp mch C theo cc trt t cu to khc

nhau, dn n tnh cht khc nhau.

V d: C4H10 (butan) c cc ng phn sau:

CH3 - CH2 - CH2 - CH3n-butan

CH3 - CH - CH3

CH3iso-butan

2.1.2. ng phn v v tr nhm chc

ng phn v v tr nhm chc l nhng ng phn c cng nhm chc, ch khc nhau v

v tr nhm chc trn mch C.

V d: ancol C3H7OH c hai ng phn v nhm chc sau:

CH3 - CH2 - CH2 - OH

propanol-1

CH3 - CH - CH3

OH propanol-2

Hay: C6H4CH3OH c cc ng phn v v tr nhm OH sau:

CH3

o-cresol

OH

CH3

m-cresolOH

CH3

p-cresolOH

2.1.3. ng phn v chc hu c

Nhm chc l nhm c trng cho tnh cht ha hc ca hp cht. ng phn v chc

hu c l ng phn to ra cc nhm chc khc nhau ca hp cht c cng thnh phn.

V chc ancol v ete: CH3 CH2 OH v CH3 O CH3

V chc axit v este: CH3COOH v HCOOCH3

V chc andehit, xeton v ru:

CH3 CH2 CHO ; CH3 CO CH3 ; CH2 = CH CH2 OH.



Trang 17

V bc ca nhm chc: CH3 CH2 CH2 NH2 ; CH3 NH CH2 CH3

CH3

N CH3CH3

2.1.4. ng phn h bin (tautome)

ng phn h bin l ng phn ca hai cht c cng thnh phn nhng khc nhau v cu

to. Hai cht ny trng thi chuyn ha ln nhau:

CH3 - C - CH2 - C - CH3

O O

CH3 - C = CH - C - CH3

axetyl xeton 2-hodroxyl-2-pentenon

O

OH

Chuyn ha ny c gi l h bin xeton anol. Ngoi ra trong hu c cn gp nhiu

dng h bin khc.

CH - N = O C = N - OHNitroso - oximino

NH - C = O N = C - OHAmido - imidol

Nguyn nhn gy ra ng phn h bin l do s chuyn ch ca nguyn t H trn cc

trung tm O, N,

2.2. ng phn lp th

2.2.1. ng phn hnh hc (ng phn Cis Trans)

Cc ng phn khc nhau v v tr cc nhm th I vI mt phng lin kt i, hoc i

vi mt phng ca vng (i vi hp cht c cu to vng)

Cl

C = C

H

Cl

H

Cis-1,2-dicloetenCl

C = C

H

H

Cl

trans-1,2-dicloeten

H H

CH3 CH3Cis-1,2-dimetyl xiclohexan

CH3 H

H CH3Trans-1,2-dimetyl xiclohexan

iu kin c ng phn hnh hc:

- Phn t phi cha lin kt i hoc vng kn.

- Cc nguyn t C c cha lin kt i v vng kn phi lin kt vi hai nguyn

t hoc 2 nhm th c bn cht khc nhau.

Khi hai nhm th cng pha ta c dng ng phn cis, hai nhm th khc pha cho

dng ng phn trans.

ng phn cis v trans khc nhau v tnh cht vt l. Nhit nng chy ca cis thp hn

trans, nhng nhit si ca cis li cao hn nhit ca trans.

V d, diphenyl butadien c 3 ng phn:



Trang 18

C = C

C = C

C6H5

H

H

H

H

C6H5

trans - trans

C = C

C = C

C6H5

HH

H

H

C6H5

trans - cis

C = C

C = CC6H5

HH

HH

C6H5

cis - cis

S ng phn ca phn t c n ni i tnh theo cng thc:

N = 2n-1 + 2p-1

N l s chn th p = 2n

, n l s l th: p = 21+n

2.2.2. ng phn cu dng

Nh chng 1 v lin kt ha hc trnh by lin kt c c ch xen ph cc obitan lai ha dc theo trc ni hai tm ht nhn. V vy, cc nguyn t hay nhm nguyn t c kh nng

quay quanh lin kt ny m lin kt vn tn ti.

Do n ng khng gian, do khong cch thay i ca cc nguyn t, nhm nguyn t khc

nhau khi quay quanh lin kt th nng tng tc thay i. Nng lng tiu tn quay khong 4

kcal/mol nh hn rt nhiu so vi cc nng lng khc.

Mi trng thi ca nguyn t, nhm nguyn t trong khng gian c dng hnh th xc nh

v nng lng tng tc nht nh. Dng hnh th ny gi l cu dng.

Cc cu dng hnh thnh khi quay quanh lin kt xch ma c nng lng khng khc nhau

lm, kh tch ra ring c. Trong v s v tr trong khng gian, c mt s v tr trong khng gian

m cc nguyn t, nhm nguyn t c khong cch xa nhau nht v tng tc nhau s nh

nht. Cu dng to thnh trong trng thi ny s bn nht. iu kin bnh thng cc phn t

thng tn ti cu dng ny.

biu din cc cu dng trn mt phng m th hin c cu trc khng giam 3 chiu.

Vic lm ny khng n gin vi cc phn t c nhiu nguyn t. V vy, phi c mt hnh thc

biu din tng trng khc. Sau y minh ha mt s cch biu din n gin cu dng phn t.

Biu din theo phi cnh: Cu dng ca buttan

CH3

CH H

CH3

CH H

CH3

CH H

CH3

HHC

CH3

CH H

CH3

HHC

CH3

CH H

CH3

CH H

Theo Newman, nt m th hin lin kt hng ra ngoi t giy trc mt ngi quan st,



Trang 19

nt thng biu din lin kt nm trn t giy, nt chm chm nm pha sau t giy.

CH3

H HCH3

HHH

H3C

H

CH3

HH

Biu din theo Newman cu dng ca butan.

a) ng phn cu dng mch h

Metan c cu trc mt t din u, gc lin kt 109028, di lin kt C H bng 1,1A0.

N c cu hnh xc nh v khng c ng phn cu dng. Etan l cht u tin ca ankan c kh

nng tn ti ng phn cu dng.

Khi nhm metyl ca etan quay quanh lin kt xchma 3600, cc v tr nguyn t H trong

phn t cng thay i, th nng tng tc ca chng cng thay i theo.

S bin thin th nng tng tc (nng lng tng tc) ca nguyn t H khi nhm CH3

quay t 0 3600 c biu din trn hnh 3.1:

HH

H

H

H

H HH

H

HH

HH

H

60 180 3000 120 240 360 Hnh 2.1: Gin th nng

Phn tch cu dng ca metan trn gin nhn thy cc v tr gc quay 600, 1200, 3000

tong ng vi cu dng c nng lng tng tc cc tiu. l cu dng xen k (cu dng

trng).

Cc hp cht kiu X3C CX3 u c gin th nng tng t nh etan. Nhng i vi

butan v xut hin hai nhm th ln CH3 so vi nguyn t H, cho nn gin th nng tng tc

c dng khc, khng n iu nh etan, R rng tng tc ca nhm CH3 vI H s khc tng

tc ca CH3 vi CH3 bn cnh v tng tc ca H vi H. Cho nn khi quay vng 0 3600 butan c

th hnh thnh cc cu dng c trng nh hnh 2.1.

Butan khc vi etan c hai dng bn: cu dng ng vi nng lng cc tiu s (1) v (3),

kcal

/mol



Trang 20

(5), cu dng (1) gi l cu dng i (anti) v cu dng lch (gaucher) s (3). Ring cu dng lch

phi v cu dng lch tri (3) v (5).

CH3

CH3

CH3

CH3CH3

CH3CH3

CH3H3C

CH3

H3C

CH3

(1) (2) (3) (4) (5) (6)

12060 180 240 300 360

3

6

kcal/mol

Hnh 2.2: Gin th nng ca butan

nhit 3000K butan tn ti cu dng (1) khong 2/3 v khong 1/3 cu dng (3) v

(5).

S cu dng ca phn t c n lin kt nh trn c th c 3n cu dng khc nhau. b) ng phn cu dng mch vng

giI thch mt s mch vng bn v mt s mch vng khng bn Bayer a ra thuyt cng vng. Vng c gc bng 109o28 l vng chun, vng bn. Cc vng c gc cng lch vi

vng chun c sc cng vng ln v km bn.

Gc ha tr c tnh theo cng thc: ( )2

2180 n, trong n l s cnh mch vng.

lch c tnh theo cng thc: 2281090 x

, trong x l gc ha tr ca vng.

Theo thuyt Bayer vng 5 cnh v 6 cnh c lch nh v sc cng vng nh, l vng

bn nht.

Cc vng ln hn v nh hn vng 5 v 6 c sc cng vng ln km bn. Nhng thc t

cng c nhiu vng ln c tnh bn cao.

V sau Sahse, Mohz, Pitre cho rng cc mch vng 6 cnh v ln hn 6 cnh khng c

cu dng phng m c cu dng khng gian, ngha l cc nguyn t H v cc nguyn t C khng

(1)

(2)

(3)

(4)

(5)

(6)



Trang 21

nm trn mt mt phng. Do chng y nhau to ra cu dng c th nng tng tc nh nht

v ng thi cng to ra cu trc bn c gc gn bng vi gc chun 109028.

Th d vng 6 cnh xyclo hexan c mt cu s cu dng in hnh nh hnh 2.3:

H

H

H

H

H

H

H

(a)H

H(e)

H

H

H

H(a)H

H

H

H

H

H

H

H

H

H

H(e)

Dng thuyn (cu dng C) Dng gh (cu dng Z)

H

H

H

H

H(a)

(He)

H

H

H

H

HH

HH

H(e)H(a)

H

Dng gh Dng xon

HH

H

H

H

H

H

H

H

H

H

H

H

H

H

H

Dng na gh Dng thuyn

Hnh 2.3: Cc cu dng ca xyclo hexan

nhit bnh thng phn t xyclo hexan c gn 990 tn ti dng gh. Cu dng gh

c nng lng nh v bn hn cu dng thuyn.

Nguyn t H v tr equatorial (e) l v tr thun li v mt khng gian v nng lng, cho

nn cc nhm th u c xu hng nh hng hoc chuyn v tr v equatorial (e).

Th d, metyl xyclohexan nhit bnh thng gn 95% nhm metyl v tr (e) v

khong 5% v tr axial (a).

Trong trng hp mch vng c hai nhm th: nh vng 6 cnh s c cc ng phn Cis

v Trans nh sau:

Cis: ea, ae: v tr 1,2 Trans: aa, ae v tr 1,2

ea, ae: v tr 1,4 ee, aa v tr 1,4

aa, ae: v tr 1,3 ae, ae v tr 1,3

2.2.3. ng phn quang hc



Trang 22

a) Cht hot ng quang hc c C i xng

iu kin xut hin ng phn quang hc l cc cht c phn t cu trc bt i xng

trong c th bt i xng phn t hoc c nguyn t C bt i xng.

hnh dung v C bt i xng ta nhc lI

thuyt ho lp th ca Lben v Vanhp v cu trc

metan. Theo hai ng phn t metan c cu trc

khng gian trong 4 nguyn t H phn trn 4 nh

ca t din u v trung tm ca t din l nguyn

t C, hc ho tr (HCH) bng 109028.

Thuyt ny cn gi l thuyt cacbon t din.

C

H

H

HH

Hnh 3.8: Cau dang hnh hoc cua phan t CH4 theo thuyet lai hoa.

Hnh 2.4: Cu trc dn xut ca metan

Nu thay 4 nguyn t H trong CH4 bng 4 nhm th a, b, c, d khc nhau th nguyn t C

ny c gi l nguyn t C bt I, k hiu l C*. Vic biu din cc ng phn quang hc bng

hnh t din nh trn mt phng khng phi trng hp no cng thun li v vy nm 1891,

E.Fischer ngh s dng cng thc chiu phng thay cho cc cng thc t din.

Tu thuc vo vic chn cnh t din l cnh nm ngang v quay v pha ngi quan st

m c th c cng thc chiu khc nhau.

a

b cd b c

a

d

b c

a

d

Hnh 2.5: Cng thc chiu thng ca Fischer

b) ng phn quang hc (cc dng cu hnh)

Nh ni trn, phn t c cu trc bt i xng u c kh nng to ra ng phn

quang hc. Trc ht chng ta lm quen vi trng hp n gin c mt C* l axit lactic:

CH3 C* COOH

H

OH Axit ny c hai i quang (hai cht nghch quang) l ng phn quay phi, k hiu l (d)

hoc (+) gc quay theo chiu kim ng h v ng phn quay tri, k hiu l l hoc (-), gc quay

ngc chiu kim ng h.

Xem hnh 2.6, hai i quang ny (hai cu hnh) chng rt ging nhau nhng khng th xem

chng kht ln nhau c, chng i xng nhau nh vt v nh trong gng, nh bn tay tri v

bn tay phi. Chng l hai ng phn quang hc c tnh cht l ho ging nhau, ch khc nhau kh



Trang 23

nng lm quay mt phng phn cc nh sng ca mt sang phi, mt sang tri v khc nhau v

hot ng sinh vt.

COOH

OHH

CH3

COOH

HO H

CH3

hay:

COOH

CH3

OHH

COOH

CH3

HHO

Gng

Hnh 2.6: Cu hnh ca axit lactic

Mt cp nghch quang nh hnh 2.6 c gc quay v tr s tuyt i bng nhau nhng khc

nhau v du. Hn hp 50% ng phn quay phi v 50% ng phn quay tri cng mt phn t

bt i gi l hn hp Raxemic (bin th raxemic).

D nhin hn hp raxemic c tr s quay cc bng khng.

Cc hp cht propadiol-1,2, andehit glyxeric l cht c mt C* v cng c mt cp i

quang nh axit lactic.

BI TP

2.1. Vit cng thc cu trc cc ng phn hnh hc (nu c) trong mi trng hp sau:

(A): CH3 CH = CH CH3 (E): CH3 CH = CH CH = CH CH3

(B): (CH3)2 CH = CH CH3 (F): CH3 CH = CH COOH

(C): CH3 CH = CH C6H5 (G): 1,1-imetyl xiclohexan

(D): CH3 C C CH3 (H): 1,2-imetyl xiclohexan 2.2. Khi qut v iu kin cn v c ng phn hnh hc?

2.3. Nguyn t cacbon bt i l g? iu kin xut hin ng phn quang hc l g? Nu th d

minh ho?

2.4. Cht no di y c th c ng phn quang hc? S lng ng phn l bao nhiu?

(A): CH3 CHBr CH3 (D): CH3 CHOH COOH

(B): CH3 CHBr CH2 CH3 (E): HOOC CH2 CHNH2 COOH

(C): CH3 CHBr CHBr CH3 (G): HOOC CHOH CHOH COOH

2.5. Cu dng l g? Vit cng thc cu dng bn ca etan; propan; butan; isopentan; 1,2-iclo

etan.


Chng 3: S tc dng tng h cc nguyn t trong phn t http://www.ebook.edu.vn

Trang 24

Chng 3: S TC DNG TNG H CC NGUYN T TRONG PHN T

Cc lin kt cng ho tr trong phn t cc cht hu c b thay i nhiu so vi lc chng

mi c hnh thnh. l do cc nguyn t, nhm nguyn t trong phn t lun lun tc dng

tng h ln nhau sp xp li mt in t trong cc lin kt, to ra mt phn t c cu

trc thch ng vi thnh phn khc nhau to ra n.

Cc tnh cht l ho, kh nng phn ng ho hc ca mI hp cht hu c u b nh

hng mnh bi tc dng tng h ny. Ngi ta bit c s tc dng tng h nh qua cc

hiu ng: hiu ng cm ng, hiu ng lin hp (cng hng), hiu ng siu lin hp, Sau y

chng ta ln lt nghin cu cc hiu ng tc dng tng h trong ni phn t cc hp cht hu

c.

3.1. Hiu ng cm ng

Hiu ng cm ng l s tc dng tng h cc nguyn t, nhm nguyn t trong phn t

cc hp cht H Cno hoc H - Ckhng no khng lin hp gy ra.

Hp cht H C khng no c lin kt pi lin hp vi lin kt xch ma s tc dng tng h

trong h ny phc tp, cho nn tm ra mt s qui lut tc dng cm ng ta ch xt trong h hp

cht H C no v cha no khng lin hp.

Trc ht ta i xt mt s th d sau:

CH3 CH2 CH2 CH3 : n butan

HCOOH c pKa = 3,7 ; CH3 COOH c pKa = 4,7; C2H5 COOH c pKa = 4,9

HO CH2 COOH c pKa = 3,0; Cl CH2 COOH c pKa = 2,9.

Trong phn t butan ch c hai nguyn t C v H. Hai nguyn t ny c m in gn

bng nhau. Cho nn cc lin kt xchma trong phn t hu nh khng phn cc. Nguyn t H

khng gy ra hiu ng. Ngi ta ly hiu ng ca H bng khng so snh vi cc trng hp.

Cc th d trn khi thay th nguyn t H axit fomic bng nhm nguyn t khc s nhn cc axit

c axit khc nhau.

Thay H bng nhm -CH3 v C2H5. Tnh axit gim so vi axit fomic. Theo l thuyt in t

nhm CH3 v C2H5 khng phi l nhm y in t ho tr ra khi mnh v pha nhm COOH,

lm cho lin kt O H gim s phn cc so vi nhm O H trong HCOOH. H kh phn ly ra nn

tnh axit gim.

H C C O H

H

H O

H C C C O H

H

H O

H

H

pKa ca axit propionic ln hn pKa ca axit axetic. iu ny chng t nhm etyl y mnh

hn nhm metyl.

Hai axit cui cng trong phn t c nguyn t Oxy v Clo l hai nguyn t c m in



Trang 25

ln. Chng c kh nng ht cc in t lin kt khc v mnh. Do cp in t lin kt O H b

lch v pha Oxy nhiu hn, lin kt O H tr nn phn cc mnh hn so vi axit fomic, S

phn ly H mnh hn nn axit tng ln.

Qua cc th d chng ta c th tm ra mt s quy lut tc dng tng h trong phn t nh

sau:

3.1.1. Khi nim hiu ng cm ng

Hiu ng cm ng: l s tc dng ca cc nguyn t, nhm nguyn t c m in ln lm chuyn dch in t lin kt xch ma, gy ra s phn cc phn t. Hay ni cch khc s tc

dng tng h gy ra t mt trung tm nguyn t hoc nhm nguyn t c m in ln truyn

i dc theo mch cacbon, lm nh hng n cc nguyn t, nhm nguyn t khc trong phn t

gi l tc dng cm ng, gy ra hiu ng cm ng.

3.1.2. Phn loi hiu ng cm ng

Hiu ng cm ng ca nguyn t hay nhm nguyn t c th c gi tr dng hoc m v

k hiu bng ch I. Du tr (-I) dng ch hiu ng cm ng gy ra bi nguyn t hay nhm

nguyn t ht in t, gi l hiu ng cm ng m.

Ngc li, nguyn t hay nhm nguyn t gy ra hiu ng bng cch nhng (y) in

t, th l hiu ng cm ng dng (+I). Chiu chuyn dch mt in t theo hiu ng cm

ng c m t theo bng mi tn thng:

//+C

/+C /+C X

X c m in ln v trung tm gy ra hiu ng cm ng: /// +++ >> , chiu ca tc dng cm ng c biu th bng mi tn dc theo lin kt.

S phn cc cm ng c m t trn lun lun c sn trong phn t v n do cc yu

t cu trc trong phn t gy ra. l s phn cc tnh (Is). Bn cnh , cn c s phn cc

ng do hiu ng cm ng ng (I). Tuy nhin lin kt xch ma l nhng lin kt bn, cho nn ta t

gp hiu ng I v trong thc t ngi ta thng dng v hiu hiu ng v phng din tnh thi.

Cc nhm nguyn t gy ra hiu ng cm ng m (-I) l nhng nguyn t, nhm nguyn

t c m in ln, l cc ion dng c kh nng ht cc in t lin kt xch ma v pha mnh.

Th d: (-I): CN > NO2 > F > Cl > Br > I > OCH3 > C6H5

Hiu ng cm ng dng (+I) gm cc gc ankyl, cc iion m, c kh nng y in t

lin kt khi mnh.

Th d: (+I): (CH3)3 > (CH3)2CH > CH3CH2 > CH3 > H

3.1.3. c im ca hiu ng cm ng

Hiu ng cm ng pht sinh v truyn i dc theo lin kt xch ma tng i nhanh, nhng

yu dn v tt i cng nhanh, ch qua 4, 5 lin kt xch ma hu nh mt i.



Trang 26

3.2. Hiu ng lin hp

3.2.1. nh ngha

Khc vi hiu ng cm ng, hiu ng lin hp th hin nhng phn t c h thng lin

kt pi v xch ma lin hp. Ngha l trong c lin kt pi lun phin lin kt xch ma v h lin hp

m rng. N gm nhng phn t c nguyn t hoc nhm nguyn t c cp in t khng lin

kt (:) lin kt trc tip vi h lin hp. Cp in t ny s lin kt vi lin kt pi ca h lin hp v

h lin hp ny c ko di thm, n c gi l h lin hp m rng.

Th d:

CH2 = CH - CH = CH2 CH2 = C - CH = CH2 CH2 = CH - Cl

CH3butadien-1,3 isopren vinyl clorua

benzen cyclohexandien

p-quinon

napthalen

phenol

OH

Npiridin

NH2

anilin

c im ca h lin hp: khng c lin kt xch ma v lin kt pi thun tu. Cc in t pi trong h lin hp khng nh c mt ch, chng c gii to trong ton h. Cc in t pi

khng thuc mt nguyn t cacbon no. Chng c kh nng phn ng cao hn in t pi trong

olefin mc d h lin hp v mt nng lng bn hn h khng lin hp.

th hin chiu ca dch chuyn in t pi, cng nh s phn b lI m in t pi

trong h c th dng hai cch sau:

Biu din bng mi tn cong:

CH2 = CH - Cl CH2 = CH - CH = CH2

:OH :NH2 C - H

O

Biu din bng phng php cng hng (mesome): Phng php ny da vo c im

ca h lin hp cc in t pi khng nh c ti mt ch, cho nn kh dng mt cng thc c in

no th hin c y trng thi thc ca h. Phng php cng hng cho rng mt phn



Trang 27

t ca h lin hp phi c biu din t nht hai cng thc c in tr ln (cn gi l cng thc

gii hn hay cng thc cng hng) cng thc thc l cng thc trung gian gia cc cng thc

.

CH2 = CH - CH = CH2 CH 2 - CH = CH - CH2 CH2 = CH - CH - CH2+ -+ -

Phng php ny c p dng nhiu gii thch c ch phn ng. Trong phn ny ta

ch s dng phng php mi tn cng tin li hn.

3.2.2. Hiu ng lin hp

Cc quy lut tc dng tng h trong h lin hp c nhiu im khc quy lut tc dng

cm ng trong h khng lin hp. Nhiu trng hp khng th gii thch c nu ch s dng

mt hiu ng cm ng.

Hai th d sau y phn no cho thy s khc nhau .

Th d 1:

R - CHO + CH3 - CH = CH - CH =CH - CHO R - CH = CH - CH = CH - CH = CH - CHO + H2O (2)

R - CHO + CH3 - CHO R - CH = CH - CHO + H2O (1)

Mc d, trung tm gy hiu ng l nhm CHO trong trng hp (1) gn nhm CH3, trng

hp (2) cch nhm CH3 bn nguyn t C, nhng hiu ng tc dng khng gim, (th hin kh

nng phn ng (1) v (2) nh nhau).

Hiu ng cm ng khong cch xa nh vy xem nh khng cn tc dng.

Th d 2:

H COOH Ka = 6,27.10-5

F COOH Ka = 7,20.10-5

Cl COOH Ka = 10,0.10-5

Br COOH Ka = 10,0.10-5

Thay H axit benzoic bng cc nguyn t F, Cl, Br. Tnh axit u tng ln. iu ny c th

dng hiu ng cm ng gi thch c. V F, Cl, Br c m in ln ko cc in t lin kt v

pha mnh lm cho lin kt phn cc, do axit tng ln so vI axit benzoic.

F CO

O

H

Nhng mnh ca tnh axit li tng ngc li so vi quy lut tc dng cm ng, axit p-flo



Trang 28

benzoic l axit mnh nht, y yu hn axit p-brom benzoic. Nh vy trong h lin hp ngoi

hiu ng cm ng cn c hiu ng khc l hiu ng lin hp.

F CO

O

H

. .

. . Hiu ng lin hp c th hiu iu l s tc dng tng h ca cc nguyn t, nhm

nguyn t trong h lin hp lm chuyn dch cc in t lin kt pi gy ra s phn cc phn t.

Hiu ng lin hp cng c hiu ng lin hp tnh v ng. Khi mt phn t cha ni i

lin hp tham gia phn ng cng vi hiu ng lin hp tnh c thng xuyn s xut hin hiu ng

lin hp ng. N biu hin bng s phn b li mt in t m hiu ng tnh phn b. Khi

phn t trng thi bnh thng hiu ng ng khng tot ra. Trong h ch c lin kt xch ma bn

vng, hiu ng cm ng ng khng ng k c th b qua, nhng trong h lin hp pi, hiu ng

ng ng vai tr quan trng gii thch c ch phn ng.

Hiu ng lin hp gm hai loi l hiu ng lin hp dng (+C) v hiu ng lin hp

m (-C) (ch C: conjugation).

Hiu ng +C: gm cc nguyn t, nhm nguyn t c cp in t khng lin kt (:) s gy

ra hiu ng lin hp dng: Trong chu k v phn nhm theo chiu tng ca in tch ht nhn,

hiu ng lin hp dng s gim.

F > Cl > Br > I

NH2 > OH > F

OR > SR > SeR

Cc nguyn t v nhm nguyn t ny cho hiu ng +C v cm ng (-I) ngc chiu

nhau. Hiu ng lin hp m (-C): gm cc nguyn t, nhm nguyn t cho C thng l nhng

nhm c lin kt pi.

HO CO

O

H

. .

. .

NO2, COOH, CHO, CONH, C N, COR, -SO3H. Trong : C = O > C = NR > C = CR2

NO2 > CN > CHO > COOH

Cc nhm ny c hiu ng C v hiu ng I cng chiu nhau, trng hp ny hiu ng

c tng cng.

Cng nh hiu ng cm ng, hiu ng lin hp mnh nhng nguyn t c m in

ln, nhm nguyn t c m in mnh hn s chi phi chiu ca hiu ng.



Trang 29

CH3 - O - CH = CH2+C -C

NO2

+C -C

NH2

-C +C

c im ca hiu ng lin hp:

- Hiu ng lin hp xut hin nhanh, lan truyn trong h cng nhanh v gim khng

ng k khi mch ko di (xa trung tm gy hiu ng).

- Hiu ng lin hp cn ph thuc vo yu t tp th, khi h gim tnh cht lin hp (cu

to phng) th hiu ng lin hp cng gim theo. N khng c hiu lc khi h mt tnh

cht ng phng.

3.3. Hiu ng siu lin hp

y l hiu ng c bit, c th ni l trng hp ring, trng hp m rng ca h lin

hp theo kiu . Hiu ng ny ch cho trng hp lin kt CH cch lin kt mt lin kt (hiu ng cm ng - , lin hp - , n - , siu lin hp - ). Th d:

H C CH CH2

H

H

H C C H

H

H O

H C C N

H

H

CH3 C CH CH2

H

H

CH3 C C H

H

H O

H C

H

H

Trng hp cc iion dng cng cacboni cng c tc dng nh ni i :

H C C

H

H

+ CH3 C C

H

H

+

y ch c lin kt C H c vit tch ri ra nh trn mI tham gia tc dng siu lin hp vi in t pi. Obitan nguyn t H cng mt lc xen ph vI obitan ca C lin kt v obitan pi.

Cc in t lin kt tng tc vi in t pi gy ra hiu ng siu lin hp. C th biu din s tc

dng siu lin hp nh sau:



Trang 30

H C C

H

H

+H C CH CH2

H

H

H C C H

H

H O

H C C N

H

H

Kt qu tng tc lin hp ny di lin kt CC gn lin kt pi ngn hn trng hp bnh thng v c bit l hiro CH tr nn linh ng th hin trong cc phn ng ancol ho v cc phn ng khc.

chng minh s c mt tng tc gy ra hiu ng siu lin hp chng ta phn tch mt

s th d sau:

CH3 CH = CH C2H5 + HCl Theo hiu ng cm ng nhm C2H5 cho hiu ng +I mnh hn nhm CH3 v vy sn phm

cng hp l:

CH3 CH = CH C2H5 + HCl CH3 CH2 CHCl C2H5 Nhng thc nghim nhn c nhm CH3 > C2H5 nn:

CH3 CH = CH C2H5 + HCl CH3 CHCl CH2 C2H5 Nh vy, cc nhm ankyl khi gn lin kt pi gy ra hiu ng siu lin hp ngc li hiu

ng cm ng.

3.4. Hiu ng khng gian

Nguyn nhn gy ra hu ng khng gian l do kch thc cc nhm th ln nh hng

nhau. Kch thc cc nhm, cc ion ln cng knh cn tr cc tc nhn kh tip cn nhau, kh to

thnh trng thi chuyn tip trong phn ng.

c bit, cc phn ng xy ra v tr octo ca nhn benzen, nh hng khng gian cc

nhm th chng nhng gy kh khn v tr th vo octo m cn lm mt tnh cu to phng nhm

th vi nhn benzen. Do , phn ng nhn benzen thay i.

NCH3 + IC2H5 N

CH3+ IC2H5(1)

(2)

Phn ng (1) thc hin kh hn phn ng (2) do mhm CH3 n ng khng gian CH3.



Trang 31

BI TP

3.1. Hiu ng cm ng l g? Nu c im quan trng nht ca hiu ng cm ng ?

3.2. a) Sp cc nguyn t v nhm nguyn t theo chiu tng dn ca hiu ng cm ng m trong

mi dy sau y:

F ; Cl ; Br ; I

OH ; NH2 ; F

b) Sp cc nhm nguyn t theo chiu tng dn ca hiu ng cm ng m trong dy sau

y: CH3 ; C(CH3)3 ; CH2CH3 ; CH(CH3)2.

3.3. Hiu ng lin hp l g? Nu c im quan trng nht ca hiu ng lin hp?

3.4. a) Sp xp theo chiu tng dn ca hiu ng +C trong mi dy sau y:

F ; Cl ; Br ; I

OH ; NH2 ; F

b) Sp xp theo chiu tng dn ca hiu ng -C trong mi dy sau y:

>C = O ; >C = NH ; >C = CH2

3.5. Cho ba hp cht cha oxi: CH3OH; C6H5OH; HCOOH. Hy cho bit nguyn nhn ca tnh axit

trong mi trng hp sau. So snh tnh axit ca ba cht . Gii thch?

3.6. Cho ba hp cht cha nit: NH3; CH3NH2 ; C6H5NH2. So snh tnh baz ca ba cht . Gii

thch?

3.7. Gii thch ti sao khi cho HCl tc dng vi penten-2 sinh ra ch yu 2-clopentan?


Chng 4: Phn ng hu c http://www.ebook.edu.vn

Trang 32

Chng 4: PHN NG HU C

4.1. Mt s khi nim chung

Nh chng ta thng ni phn ng ho hc l qu trnh bin i cht ny thnh cht khc,

trong c qu trnh ph v lin kt c to ra lin kt mi. Qu trnh ph v lin kt c c th to

ra ion, to ra gc t do.

+ -. . + -A + B AB A B A + B

Cc phn ng phn cc, cc ion, cc gc t do tc dng cc cht khc to ra cht mi.

Phn ng ho hc c s tham gia ca gc t do gi phn ng theo gc t do. Cc gc t

do c nng lng ln, thi gian tn ti ngn, c kh nng cho phn ng cao. Cc hp cht hyro

peroxit v peroxit d phn hu cho gc t do.

Phn ng ho hc c s tham gia ca cc ion gi phn ng ion. Tc nhn tng tc A+ gi

l tc nhn i in t. Tc nhn B- gi l tc nhn i nhn. Tc nhn i nhn cng l mt baz ca

Lewis, tc nhn i in t l mt axit ca Lewis.

Trong phn ng oxy ho kh c th xem tc nhn i nhn l cht kh, cn tc nhn i in

t nhn in t ca tc nhn i nhn nn c th xem l cht oxy ho.

Nh vy cc phn ng ho hc: phn ng cng hp, phn ng th, phn ng tch loi,

c th xy ra theo c ch gc t do, hoc c ch ion. Phn ng theo c ch ion c c ch i in

t v c ch i nhn.

Tu thuc vo s lng cc phn t hoc ion, tham gia vo giai on quyt nh tc

phn ng m c loi phn ng n phn t, lng phn t hoc nhiu phn t.

Trong phn ng ho hu c, cc cht tham gia phn ng c th thc hin trng thi hi,

trng thi lng, trng thi rn c dung mi ha tan hoc khng dung mi ho tan.

4.2. c im ca phn ng hu c

Phn ng ho hc hu c khng nhng c nhiu v s lng, rt phc tp v v c ch

m cn c nhng c im ring sau y:

- Phn ng xy ra thng l chm.

- Phn ng xy ra qua nhiu giai on (phn ng ni tip).

- Phn ng xy ra song song nhau (phn ng cnh tranh sinh ra sn phm ph).

Phn ng hu c thng xy ra khng qua giai on phn ly ra ion, m qua giai on to

ra trng thi trung gian gi l trng thi phc hot ng hay trng thi chuyn tip ri sau to ra

cht mi. Bng con ng qua trng thi chuyn tip phn ng tiu tn nng lng t hn nhiu

so vi phn ly ra ion.

4.2.1. Tc phn ng

Cc phn ng ho hc xy ra mt giai on nh:

aA + bB eE



Trang 33

Vn tc ca phn ng c xc inh: v = k[A]a [B]b. Phn ng bc a i vi A, bc b i

vi B v bc ca phn ng l (a+b).

Cc phn ng qua nhiu giai on vic tnh vn tc tr nn phc tp hn. Trng hp ny

c th tnh gn ng l b qua cc giai on phn ng nhanh, giai on chm nht l giai on

quyt nh tc phn ng.

4.2.2. Phn ng cnh tranh

c im c bit trong phn ng hu c l mt trong cc cht nh nhau phn ng xy ra

nhiu hng khc nhau cho sn phm chnh v sn phm ph (phn ng song song nhau).

Th d: Cht A ng thi phn ng vi cht B v D (hoc cng mt cht B nhng v tr

khc nhau trong phn t):

A + B 1K E A + D 2K G i vi phn ng mt chiu, c cng bc phn ng th tng quan gia sn phm E v G

to thnh khng i trong qu trnh phn ng. T l ny l thc o hot tnh tng tc ca B v D

i vi A.

[ ][ ] 2

1

KK

GE =

4.2.3. Trng thi chuyn tip

Thuyt va chm: mun phn ng ho hc xy ra cc cht tham gia phn ng phI va chm

nhau. Ngi ta tnh c s va chm gia hai phn t trong 1 giy th tch 1cm3 v 150C

khong 1014 va chm. Nu mi va chm u xy ra phn ng th tc phn ng rt ln. Thc s

khng phi va chm no cng xy ra phn ng. Cc va chm gy ra phn ng ch i vi phn t

c nng lng cao, nng lng mi va chm u sinh ra cht mi. Nng lng ny c gi

l nng lng hot ho.

Nghin cu v vn ny Arenius a ra phng trnh xc nh s ph thuc hng s vn

tc phn ng:

K = p.z. RTE

e

Vi: K l hng s vn tc

z l s va chm (vn tc phn ng t l thun vi z)

E l nng lng hot ho

p l tc nhn xc sut, tc nhn lp th. N cho bit s khc nhau gia tc thc

v tc tnh theo l thuyt (p = 10-1 10-3).

Vic tnh yu t xc sut p khng n gin, v vy thuyt va chm b hn ch p dng cho

nhiu phn ng. Thuyt trng thi chuyn tip ra i. y l thuyt c gi tr trong vic gii quyt

cc c ch phn ng ho hc.



Trang 34

Xt phn ng ho hc: A + BC AB + C Mun phn ng ho hc xy ra, trc ht BC phi phn ly thnh B v C. Sau B kt hp

vi A to ra AB. Phn ng thc hin bng con ng ny phi tiu tn nng lng ln phn ly

BC thnh B + C. Nng lng ny xa vi nng lng thc t cn thit to ra phn t AB.

Theo Hayle London Ingold phn ng xy ra khng qua giai on BC phn ly thnh B v

C, m BC cng A to ra trng thi chuyn tip, trng thi ny A...B...C cng nm trn mt trng

thi m bo nng lng tng tc nh nht.

C th biu din thuyt trng thi chuyn tip p dung cho kh nng phn ng h 3 trung

tm nh A + BC l:

A + BC A...B...C AB + C i vi h c 4 trung tm AB + CD AC + BD c th biu din trng thi chuyn tip:

A C

B D+

A C

B D+

A C

B D

trng thi chuyn tip

4.3. Phn ng th trong ho hc hu c

4.3.1. Khi nim

Phn ng th k hiu bng ch S (xut pht t Substitution c ngha l s thay th) l

phn ng trong mt nguyn t hay nhm nguyn t trong phn t c thay th bng nguyn

t hay nhm nguyn t khc.

Th d: CH4 + Cl2 CH3Cl + HCl CH3 Cl + NaOH CH3 OH + NaCl Phn ng trng ngng thc cht l nhng phn ng th ni tip nhau.

Phn ng th l phn ng rt ph bin trong ho hc hu c, l phn ng c nghin

cu k v rt lu i, ... Tu thuc vo bn cht tng loi tc nhn tng tc m c th chia cc

loi phn ng sau:

4.3.2. C ch phn ng th

a) Phn ng th theo c ch gc t do

,,,,,, ++ RRRRRR

Cc gc t do c to thnh c th do tc dng nhit hoc nh sng, v d:

Cc hydro peroxyt, peroxyt: HORHOOR t + O0

+ ORRROOR t ,, O0

+ ClClCl hv2



Trang 35

Cc phn ng halogen ho ankan, phn ng ankyl halogenua vi kim loi, ... l nhng

phn ng th theo gc t do.

ClMgRMgClR ++

2MgClRClMgClR ++

+ + + RMgClRMgRMgR ClR

Phn ng clo ho: R H + Cl2 hv RCl + HCl

+ ClClCl hv2

HClRClHR ++

++ ClRClClR 2 b) Phn ng th theo c ch i in t

Phn ng th i in t c k hiu l SE (21 , EE SS l phn ng n phn t hay lng

phn t). S tng qut:

R+ + R/(-)R//(+) R/ R + R//+ Th d:

CH3 I + CH3 Na

CH3 ... CH3

Na ... I

+

+ -

-CH3 CH3

NaI+

4.3.3. Phn ng th i nhn vo nguyn t C no

Phn ng th i nhn ch yu tp trung vo nguyn t C bo ho v phn ng th H

nhn benzen ngho in t.

S chung: R(-) (R:) + R/ - R// R// R + R/(-) (R/:) Vi R (-) (R:): l cc anion, cc hp cht c cp in t t do (:) nh Cl-, Br-, I-, OH-, RO-,

RS-, CN-, ROH, RCOO-, NH3, RNH2.

Cn R/ - R// l cc ankyl halogen, ru, ete, este, hp cht diazo, cc ankyl sunphat. Th d: CH3 CH2 CH2 Cl + OH- CH3 CH2 CH2 OH + Cl- C2H5 O C2H5 + HBr C2H5OH + C2H5Br c) Phn ng th theo c ch nucleophin (SN)

Phn ng th nucleophin c hai c ch: c ch n phn t ( 1NS ) v lng phn t (2NS ).

Phn ng th n phn t ( 1NS )



Trang 36

Th d:

CH3 C Cl + OH

CH3

CH3- CH3 C OH + Cl

CH3

CH3-

C ch:

CH3 C Cl

CH3

CH3

CH3 C + Cl

CH3

CH3-+ - +cham

CH3CH3

CH3 C

CH3

CH3+ -+ nhanh

CH3

C + OH nhanh

CH3

CH3CH3

CHO CH3 C OH

CH3

CH3

Giai on u l giai on ion ha to ra ion, giai on ny thng chm, cho nn tc

ion ho cng l tc ca phn ng.

Giai on hai c tnh cht ion tng tc nn c thc hin nhanh. Trc khi thc hin

giai on hai ion cacboni trung tm s chuyn t trng thi t din sang trng thi mt phng

bn hn. Nh vy nhm OH c xc sut tn cng vo hai pha nh nhau.

Phn ng th lng phn t ( 2NS )

Th d: CH3 Cl + OH- CH3OH + Cl- C ch:

HH+-

H

COH +

H

H

H

CHOH C Cl

H

H

+- HO- Cl- + Cl-

(TTCT) Giai on chm nht l giai on to thnh TTCT c s tham gia ca CH3Cl v ion OH-.

Theo thuyt TTCT, ba trung tm phn ng OH, C v Cl TTCT phi nm trn mt ng thng.

l iu kin m bo nng lng tiu tn cho phn ng cc tiu. Khi lin kt OH v C t n

hng ro nng lng chuyn tip th Cl tch ra khi C.

4.4. Phn ng tch loi trong ho hc hu c

4.4.1. Khi nim

Phn ng tch loi k hiu bng ch E (xut pht t Elimination c ngha l s tch b) l phn ng lm cho hai nguyn t hay nhm nguyn t b tch ra khi mt phn t m khng c

nguyn t hay nhm nguyn t no thay th vo.



Trang 37

Th d: CH3 CH3 CH2 = CH2 + H2 C2H5OH CH2 = CH2 + H2O Crackinh thc cht l phn ng tch loi.

Phn ng tch loi c th xy ra vi hai nhm tch ra cng mt nguyn t C hoc khc

nguyn t C. Sn phm tch loi c th l hp cht khng no, hoc hp cht vng.

Trong phn ng ng vng c phn ng ng vng kiu Dikman (hai nhm tch loi khng

cnh tranh)

Trong phn ng ng vng thng thc hin bng s tch loi, nhng c ch phn ng

tch loi kiu ng vng nhiu trng hp theo c ch th ni phn t.

Cc phn ng ng vng thng gp:

CH2Br

CH2CH2Br

+ 2Na

CH2CH2

CH2

+ 2NaBr(or: Zn/ROH)

1,3-dibrom propan Xyclo propan

ng vng to nhm poxy:

+ HClCH2 CH CH2

Cl OH OH

CH2 CH CH2

O OH

.....

Phn ng tch loi c gi tr l phn ng tch loi to ra olefin, ankin. y l phn chnh

ca chng trnh. Trc ht dn chng mt s phn ng tch loi to ra ni i thng gp trong

ho hu c.

R CH CH2 R CH CH2 + HX

H X

R CH CH2 R CH CH2 + H2O

H OH

H+

R CH CH2 R CH CH2 + H2SO4

H OSO3H

+H2O

4.4.2. C ch phn ng tch loi

a) Phn ng tch loi n phn t (E1)



Trang 38

CH3 CH2 C Cl

CH3

CH3cham CH3 CH2 C Cl

CH3

CH3+ -+

CH3 CH C CH3 + H

CH3

+CH3 CH2 C

CH3

CH3+ nhanh

CH3 C OH + H CH3 C O

CH3

CH3cham

CH3

CH3

+CH3 C CH2 + H CH3

+

CH3

CH3

+

-nhanh

H

H

+

CH3 C + H2Onhanh

Hai phn ng trn vit theo c ch loi n phn t. Giai on to ra cation cacboni l giai

on chm nht, nn l giai on quyt nh tc phn ng.

Vai tr ca dung mi phn cc i vi phn ng tch loi l sonvat ho, to kh nng cho

cht phn ly ra ion. Dung mi cng phn cc, phn ng tch loi E1 xy ra nhanh v thun li.

b) C ch phn ng tch loi lng phn t

Ging nh phn ng th 2NS , phn ng tch loi E2 cng tri qua giai on to thnh trng

thi chuyn tip.

HO ... H ... C C ... Cl- +

R CH CH2 + Cl

HO + R CH2 CH2 Cl

H

R-

H

H

(TTCT)

-H2O

-

Theo ch ch tch loi trn H+ v Cl- tch ra cng mt lc. Thc nghim xc nhn tc

phn ng ph thuc vo tc nhn tch loi (OH-).

Phn ng tch loi E2 khng nhng ph thuc vo nng tc nhn i nhn m cn ph

thuc vo sc i nhn v baz ca n, ... Nng tng ln, tnh baz tng ln phn ng tch

loi E2 xy ra cng nhanh.

Phn ng tch loi E2 r rng theo c ch cn ph thuc vo cu trc phn t cht tch

loi. Yu t cu trc y ch yu ph thuc vo bc C c H tch loi ra. Bc C cng ln nh

hng yu t khng gian cng mnh, tc nhn i nhn cng kh tip cn H+, kh hnh thnh trng



Trang 39

thi chuyn tip. Hng tch loi E2 b hn ch hoc thay i.

Cc tc nhn i nhn thng gp trong phn ng tch loi E2: H2O, CH3COO-, C6H5O-,

OH-, CH3O-, NH2-, CO32-. Trong tc nhn baz mnh RO-, OH-, NH2- d dng loi proton cho

phn ng E2.

Cc nhm chc trong phn t tch loi c kh nng tch theo E2: R3N+, R3P+, R3S+, -SO2R,

X-, OSO2R, RCOO-. Trong d tch nht l R3N+, R3P+, R3S+ cn X- cn tc nhn baz mnh mi

tch c.

4.4.3. S cnh tranh phn ng tch loi v th

C ch phn ng th v tch loi c nhng im ging nhau. Trong phn ng th bao gi

cng km theo phn ng tch loi v ngc li. T l sn phm th v tch loi ph thuc vo

nhiu yu t. Phn ng th n phn t SN1 v tch loi n phn t E1 u qua giai on to

thnh ion cacboni. Khi tng nhm th ankyl s tng kh nng tch loi E1 hn th SN1.

R CH2 CH2 X < R CH2 CHR1 X < R CH2 CR1R2 X

i vi phn ng tch loi theo c ch SN2 v E2 cng vy, vic tng nhm th ankyl s

tng phn ng E2 hn SN2.

4.5. Phn ng cng hp trong ho hc hu c

4.5.1. Khi nim

Phn ng cng c k hiu l bng ch A (xut pht t Addition c ngha l s cng

hp) l phn ng trong c hai phn t kt hp vi nhau to thnh phn t mi.

Phn ng trng hp c bn cht l phn ng cng hp nhiu ln.

Trong phn ng hu c thng gp cc dng phn ng cng hp sau:

R CH = CH2 + Cl2 R CHCl CH2Cl R C CH + 2Cl2 R CCl2 CHCl2

R CH

O

NaHSO3 CH3 C SO3H

H

ONa

+

+CH3 CH CH2O OH NH2

NH3 CH3 CH CH2

Lin kt pi l lin kt giu nng lng, c kh nng phn ng kh mnh di tc dng mi

trng bn ngoi hoc do cc hiu ng ni phn t. Cc nhm th gy hiu ng in t lm gim

hoc tng mt in t lin kt pi dn n s tng phn cc ca n.

Trng hp cc hiu ng lm tng mt in t lin kt pi, lin kt pi s tng hot ho

tc dng vi nhiu i nhn i in t. Trng hp ny chnh in t pi l tc nhn i nhn, mt

baz mnh.



Trang 40

Trong trng hp ngc li nhm th gy hiu ng lm gim mt in t pi lin kt

pi th kh nng cng hp i in t s gim, c xu hng cng hp i nhn.

Ring lin kt ba nh axetylen c kh nng cng hp i nhn ln i in t. Mt s tc

nhn i nhn mnh RO-, RCOO- trong mi trng baz, axetylen cng hp i nhn.

Phn ng cng hp c 3 c ch: cng hp i nhn, i in t v gc t do.

4.5.2. C ch ca phn ng cng hp

a) Phn ng cng hp i in t vo lin kt i C = C

Th d:

CH2 CH2 + Cl Cl CH2 CH2 CH2 CH2nhanh

Cl+

Cl-

Cl

+

+cham + Cl-

CH2 CH2

Cl+ Cl- CH2 CH2

Cl

Cl

Phn ng cng hp vo ni i C = C theo c ch i in t cn phi c mt ca dung mi

phn cc hoc xc tc nh xc tc Lewis lm cho lin kt pi d phn cc v tc nhn cng hp

phn cc (Cl2). Nh s phn cc trc nn gai on to phc nhanh. Qu trnh phc ph v lin kt to ra ion l qu trnh kh v chm. V vy tc phn ng cng hp c xc nh l gia on ph v lin kt pi to ra ion. Hn na tc nhn i in t s cng hp vo trc v c

cng hp vo giai on quyt nh ny. Cho nn phn ng cng hp vo ni i C = C l phn

ng cng hp i in t.

C ch phn ng: c ch AE

+- cham + Y-

X

nhanh

C C + X+ Y -+

C C

+ Y-

X

+C C

X

C C

Y

b) Phn ng cng hp i nhn vo lin kt i C = O

Nhm cacbonyl c kh nng cng hp rt nhiu cht (H2, HCN, NaHSO3, H2O, NH2-OH, R-

MgX, ...). Kh nng cng hp c nhiu ca nhm cacbonyl l do nguyn t O c m in ln

lm cho lin kt pi b phn cc mnh v pha O

C O+ -

phc



Trang 41

To ra hai trung tm: 1 trung tm dng (C+) v mt trung tm m (O-). Trung tm dng

s tng tc vi tc nhn i nhn, trung tm m s tng tc vi tc nhn i in t. Trong phn

cc ng ho hc trung tm dng c vai tr quyt nh cho giai on u ca cng hp i nhn.

C ch phn ng: c ch AN

nhanh

cham + X+C OO-

+ X+ Y -+ -

R1

R2C

R1

R2 Y

+ X+O-

CR1

R2 Y

OXC

R1

R2 Y

Th d:

nhanh

cham + H+C OO-

+ H+ CN--CH3

HC

CNOH

CCN

CH3

H

+ H+O-

CCN

CH3

H

CH3

H

BI TP

4.1. C ch phn ng l g? Hy minh ho bng c ch phn ng sau:

a) CH4 + Cl2 CH3Cl + HCl b) CH2 = CH2 + Br2 CH2Br - CH2Br c) CH2 = CH2 + HBr CH3 - CH2Br d) CH3 CHO + NaHSO3 ?


Chng 5: Hirocacbon http://www.ebook.edu.vn

Trang 42

Chng 5: HIRO CACBON

5.1. HIROCACBON NO

Hirocacbon no l nhng H C m trong phn t ca chng ch c nguyn t Csp3, cho

nn phn t ch c lin kt n.

Phn loi: gm hai loi H C no mch h (ankan) v H C no mch vng (xicloankan)

5.1.1. Cu trc phn t

a) i vi ankan

Phn t ankan ch c nhng nguyn t 3spC vi gc ho tr 109028/, do mch C thng ziczac v tn ti ch yu dng xen k, v l nhng dng bn (hnh 5.1)

H

H HH

HH

CH3 - CH3

H

H HCH3

HH

CH3 -CH2 - CH3

CH3

H HCH3

HH

CH3 -CH2 - CH2 - CH3

H

H CH3

CH3

HH

anti syn

Hnh 5.1: Cu dng xen k ca mt s dng ankan

b) i vi xicloankan

Xiclopropan v xiclobutan l nhng vng km bn. Do gc (CCC) b p nhiu so vi gc

bnh thng (109028/), lin kt C C trong phn t xiclopropan chng hn c hnh thnh bng

cch xen ph mt bn, chnh v vy lin kt ny km bn. Ngoi ra, nu nhn theo trc dc lin kt

C C ta thy cc nguyn t H v tr che khut nhau, yu t cng gp phn lm cho vng km

bn.

Xiclopentan v xiclohexan l nhng vng bn. Vng xiclohexan c dng gh nn gc lin

kt t din vn c bo m cn cc nguyn t H lun lun v tr xen k. Dng thuyn tuy vn

m bo gc lin kt, song c mt nguyn t H v tr che khut (hnh 5.2) nn dng thuyn khng

bn.

H

H

H

H

H

H

H

(a)H

H(e)

H

H

H

H(a)H

H

H

H

H

H

H

H

H

H

H(e)



Trang 43

HH

HH

H(e)H(a)

HHH

H

H

H

H

Dng gh Dng thuyn

Hnh 5.2: Cu dng ca xiclohexan

5.1.2. Tnh cht vt l

Gia cc phn t ankan ch c lc ht vandevan nn cc cht u dy ng ng l

nhng cht kh (t metan n butan), nhng cht sau l lng (t C5 n C19) hoc rn (t C20 tr

ln). Ni chung, khi phn t khi ca ankan tng th nhit si v nhit nng chy cng tng

theo (bng 5.1). S phn nhnh lm cho nhit si gim i.

Bng 5.1: Hng s vt l ca mt s ankan

CTPT Tn 0nct

0st d

CH4 Mtan -183 -162 0,415

C2H6 Etan -183 -89 0,561

C3H8 Propan -188 -42 0,585

n butan -138 -0,5 0,600

C4H10 Iso butan -159 -10 0,603

n- pentan -130 36 0,626

2 metyl butan (iso pentan) -160 28 0,620

C5H12

2,2 imetyl propan (iso pentan) - 9,5 -

C8H18 n - octan -57 126 0,703

C10H22 n decan -30 174 0,730

C20H42 n - icosan 37 343 0,778

Cc ankan u khng tan trong nc (hoc t tan). Ngc li chng d tan trong nhiu

dung mi hu c, ho tan c cht bo.

5.1.3. Tnh cht ho hc

So vi mt s hp cht hu c khc, ankan c kh nng phn ng rt km. iu kin



Trang 44

thng, ankan khng tc dng vi axit, baz, cht oxi ho, kim loi hot ng, ... v th ankan l

mt parafin (t ting Latin parum affinis c ngha l i lc)

Cc phn ng ho hc ca ankan thng ch xy ra khi un nng, khi chiu sng hoc c

mt cc cht khi mo v xc tc v hu ht theo c ch ng ly.

a) Phn ng th hiro bng halogen

Phn ng ch xy ra vi clo hoc brom, trong iu kin chiu sng, it khng phn ng,

cn flo gy ra phn ng n.

S phn ng: R H + X2 hv R X + HX Th d:

CH4 CH3Cl CH2Cl2 CHCl3 CCl4- HCl+ Cl2 + Cl2 + Cl2+ Cl2

- HCl - HCl- HClmetyl metyl clorua metylenclorua clorofom cacbon tetraclorua

C ch phn ng: C ch th gc t do SR

- Khi mo phn ng: X2 hv 2X* - Pht trin mch: X* + R H R* + HX R* + X X R X + X* X* li tip tc phn ng vi R H nh trn, qu trnh c lp li n ln (nu RH l CH4 n10000)

- Giai on tc mch theo cc hng sau: X* + X* X2 R* + X* R X R* + R* R R Kh nng phn ng v hng phn ng: Khi halogen ho cc ng ng ca etan c th sinh ra mt hn hp dn xut monohalogen ca nhau. Th d:

CH3 CH2 CH3

CH3 CH2 CH2Cl

CH3 CH CH3

Cl

(A)

(B)

+ Cl2-HCl hv

T l % cc sn phm ph thuc vo s lng ni cc nguyn t H cng mt loi, tc l

lin kt vi nguyn t C bc i (bc I, bc II hay bc III) v ph thuc kh nng phn ng ri ca

nguyn t H cacbon bc i . Thc nghim cho thy ri ca phn ng 1000C nh sau:



Trang 45

CI H CII H CIII H Clo ho 1 4,3 7

Brom ho 1 82 1600

Ta thy bc ca C cng cao th kh nng phn ng ca H cng ln v C bc cng cao s

cho gc t do bc cao bn hn. S khc nhau v ri trong phn ng brom ho r rt hn trong phn

ng clo ho.

Gia t l % ai ca sn phm th vi ni v ri c mi quan h n sau:

=

ii

iii rn

nra 100(%)

Trong th d v clo ho propan trn nI = 6; nII = 2; rI = 1; rII = 4,3. p dng biu thc

trn ta tnh c:

Sn phm A: aI(%) 41% Sn phm B: aII 59% Phn ng ca xicloankan vi halogen: Xiclohexan, xiclopentan, ... tc dng vi halogen tng t ankan, ngha l cho sn phm

th. Th d:

hv+ Br2 + HBr

Br

Tuy nhin, xicloprpan li tham gia phn ng cng - m vng, v vng ny km bn. Th d:

Br CH2 CH2 CH2 BrCCl4+ Br2

Ngoi phn ng cng brom, xiclopropan cn d dng cng hiro, HBr, H2SO4, ....

b) Phn ng tc dng nhit

ehiro ho hay l tch H2: Khi un nng ankan c mch ngn vi xc tc (Cr2O3, Cu, Pt, ...) xy ra phnng tch H2 to thnh H C khng no. Th d:

xt, t0 +CH3 CH3 CH2 CH2 H2

Khi nhit phn CH4, tu thuc iu kin phn ng c th thu c mui than hoc

axetylen:

xt, 10000CH4 C + 2H2

2CH4 HC CH + 3H21400 - 15000



Trang 46

Phn ng tch H2 nhng ankan c 5 7 C trong mch chnh c th dn ti s ng vng

hoc xa hn na l thm ho. Th d:

xt, t0CH2

CH2CH2 CH3

CH3CH2

xt, t0- H2 - 3H2

Crackinh: l qu trnh b gy mch C ca ankan to ra mt hn hp nhng anken v ankan c mch C ngn hn. Qu trnh ny xy ra nh tc dng n thun ca nhit (500 7000C) gi l

crackinh nhit, hoc nh cht xc tc nhi thp hn (450 5000C) gil crackinh xc tc. Th

d:

C4H10CH4 + C3H6

C2H6 + C2H4

c) Phn ng oxi ho

Oxi ho hon ton: t chy trong khng kh Khi c tia la t v oxi, ankan v xicloankan c th chy hon ton sinh ra CO2, H2O

v to nhit mnh:

CnH2n+2 + 213 +n

O2 0t nCO2 + (n+1)H2O

CnH2n + 23n

O2 0t nCO2 + nH2O

Phn ng chy ankan c dng rng ri trong cng nghip v i sng.

Oxi ho khng hon ton: Tu theo iu kin phn ng, ankan b oxi ho khng hon ton cho nhng sn phm khc nhau trong cng nghip.

Oxi ho metan:

Ni, 5000CCH4

HCHO + H2O

CO2 + 2H2

C + 2H2O

+ O2 (kk)

200 at, 300oC, Cu

thieu oxi

Oxi ha butan:

CH3 CH2 CH2 CH3

+ O2 (kk)

Mn2+2CH3 COOH



Trang 47

Oxi ho ankan cao:

+ O2 (kk)

Mn2+

R1 COOHR1 CH2

R2 CH2 R2 COOH+

Oxi ho xiclohexan:

+ O2 (40at) O

OH

150oC

ZnO, to

+ O2 , NOxiclohexanon

5.1.4. Phng php iu ch

a) Phng php tng mch cacbon

T cacbon oxyt v hiro c xc tc Fe, Co, Ni Hn hp CO v H2 cho i qua nhit 2000C v p sut kh quyn c cht xc tc st,

coban cho hn hp ankan

nCO + (2n + 1) H2 CoFeC ,,2000 CnH2n + 2 + nH2O Phn ng Wurtz Fittig (Php 1855) y l phn ng tng hp quan trng iu ch H C loi no i t ankyl halogenua v

natri kim loi.

R X + 2Na + R/ X R R/ + 2NaX

R R

R/ R/

V d: 2C2H5I + 2Na C2H5 C2H5 + 2NaI

C ch phn ng: 2C2H5I + 2Na 2 52 HC

+ 2NaI

2 52 HC

C2H5 C2H5

Nh vy c ch gc gii thch s tn to thnh sn phm chnh v ph.

Phn ng tng hp Kolbe (c 1849): in phn dd mui Na ca axit cacboxylic



Trang 48

2RCOONa + 2H2O dpdd R R + 2CO2 + 2NaOH + H2 b) Phng php gi nguyn mch cacbon

Phn ng kh ru bng axit HI m c 80% 180 2000C: Phn ng tin hnh qua hai giai on:

ROH + HI RI + H2O RI + HI RH + I2 i khi thm vo phn ng mt t phtpho eer c tc dng to ra HI bit lng HI a

vo phn ng:

3I2 + 2P 2PI3 PI3 + 3H2O H2PO3 + 3HI Phn ng kh H C khng no bng H2 c xc tc:

R CH = CH R/ + H2 0,tNi R CH2 CH2 R/ R C C R/ + 2H2 0,tNi R CH2 CH2 R/ c) Phng php gim mch cacbon

Khi ct khan mui kim hoc kim th ca axit cacboxylic vi vi ti xt s thu c H C

c mch C gim i mt nguyn t so vi axit cacboxylic.

R COONa + NaOH 0,tCaO R H + Na2CO3 Th d: CH3 COONa + NaOH 0,tCaO CH4 + Na2CO3 5.1.5. ng dng

- Dng lm nhin liu (CH4 dng trong n x hn, ct kim loi).

- Dng lm du bi trn.

- Dng lm dung mi.

- tng hp nhiu cht hu c khc: CH3Cl, CH2Cl2, CCl4, CF2Cl2,

- c bit t CH4 iu ch c nhiu cht khc nhau: hn hp CO + H2, amoniac,

CH CH, ru metylic, anehit fomic



Trang 49

BI TP

Cu 5.1: Vit CTCT v gi tn cc ankan c CTPT C5H12, C6H14 v xicloankan C5H10. Dng s la m ch r bc ca nguyn t C v gi tn CTCT tng ng.

Cu 5.2: C bao nhiu gc t do tng ng vi cng thc 94 HC

. So snh bn tng i ca

cc gc t do?

Cu 5.3: Cho n-butan phn ng vi clo theo t l 1:1 c chiu sng ta c hn hp 2 sn phm hu c v mt cht kh A.

a) Vit phng trnh phn ng v c ch phn ng.

b) So snh khi lng hai sn phm hu c, bit rng mt nguyn t H CII c kh nng

phn ng co hn 3 ln so vi mt nguyn t H CI.



Trang 50

5.2. HIRO CACBON KHNG NO

Hirocacbon khng no l nhng H C c cha lin kt i hoc lin kt ba, hoc c lin

kt i v lin kt ba trong phn t.

Ta phn bit H C c mt ni i (anken CnH2n n 2), nhiu ni i (polien), mt ni ba (ankin CnH2n-2 n 2), nhiu ni ba (poliin), c ni i ln ni ba (ankenin). Ngoi ra c nhng H C khng no mch vng, nh xicloanken, ....

5.2.1. Cu trc phn t

a) Anken

Phn t anken c lin kt i, l tp hp ca mt lin kt v mt lin kt .

C C

Lien ket xchma: do hai obitan lai hoa sp2 xen phu vi nhau tao nen

Lien ket pi: do hai obitan p xen phu ben vi nhau tao nen

V d phn t etilen c 6 nguyn t (2C v 4H), tt c u nm trn 1 mt phng cha trc

ca 5 lin kt . di ca lin kt C C l 1,34A0 (trong khi ca etan l 1,54A0) gc lin kt (HCC v HCH gn bng 1200).

Nng lng lin kt i C = C bng 616 kJ/mol, nh hn nhiu so vi nng lng ca hai

lin kt n C C (2 x 348 = 696 kJ/mol). iu chng t nng lng ca lin kt pi nh hn so

vi lin kt xchma, do lien kt pi km bn.

H

H

H

H

HH

H H

hay

Hnh 5.3: S hnh thnh lin kt pi ca etilen

Nguyn t 2spC c m in ln hn 3spC . Hai nguyn t 2spC lin kt vi nhau khng

th quay t do c, do , c th xut hin ng phn hnh hc nu mi nguyn t 2spC ni

vi hai nguyn t hoc nhm nguyn t khc nhau.

b) Ankadien

Ankadien hoc olephin l nhng H C trong phn t cha hai li kt i.

Cng thc chung CnH2n-2 (n 2) Phn loi: tu thuc vo v tr ca lin kt i trong phn t m ngi ta chia ra lm 3 loi:



Trang 51

Loi ankadien c ni i bit lp: loi ny c cng thc chung:

C C (CH2)n C C

V d: n = 1: CH2 = CH CH2 CH2 CH = CH2 (hexadien 1,5)

Loi ankadien c ni i tip cn nhau (lin nhau): loi ny c cng thc chung:

R1 C C C R2

V d: CH2 = C = CH2 alen (propadien 1,5)

Loi ankadien c ni i lin hp: loi ny c cng thc chung:

R1 CH CH CH CH R2

V d: CH2 = CH CH = CH2 (butadien 1,3)

CH2 C CH CH2

CH3 2 - metyl butadien - 1,3 (isopren)

Cu trc phn t: butadien 1,3

Trong phn t butadien 1,3 tt c 10 nguyn t (4C v 6H) v 9 lin kt (3 C C v 6 C H) u nm trn mt mt phng v to nn nhng gc lin kt 1200. Cc obitan p khng nhng xen ph bn vi nhau to thnh lin kt gia C1 vi C2 v C3 vi C4 m cn xen ph gia C2 vi C3 do xut hin obitan bao trm tt c bn nguyn t C (h.5.4)

H

H

H

H

H

H

H

H

H

HH

H

a) b)

Hnh 5.3: S xen ph cc AOp (a) to thnh lin kt chung cho ton phn t butadien (b) Hin tng xen ph obitan nh trn gi l lin hp, v do butandien 1,3 l 1 ien lin

hp.

Ankadien lin hp cng c cc cu dng khc nhau v cng c ng phn hnh hc, nu

nguyn t 2spC u mch ni vi hai nguyn t hoc nhm nguyn t khc nhau. Th d:

CH3 CH = CH CH = CH2 c hai ng phn hnh hc



Trang 52

CH3 CH = CH CH = CH C2H5 c 4 ng phn hnh hc

c) Ankin

Ankin l lo hirocabon mch h, trong phn t ca chng c lin kt ba.

Cng thc phn t CnH2n-2 (n2) Phn t cha mt lin kt ba, l tp hp ca lin kt (do hai AOsp to nn) v hai lin kt (do 4 AO2p xen ph nhau).

180o180o

H HH C C H

a) b)

Hnh 5.4: S hnh thnh lin kt xch ma (a) v lin kt p (b) ca C2H2

di lin kt C C ch bng 1,2A0 (ngn hn C = C). Lin kt Csp- H phn cc mnh hn HC 2sp v m in ca 2spsp CC .

Nng lng lin kt ba bng 813 kJ/mol, nh hn nhiu so vi nng lng ca 3 lin kt

n (3 x 348 = 1044 kJ/mol); iu cng chng t lin kt pi linh ng.

5.2.2. Tnh cht vt l

Hirocacbon khngno c nhiu tnh cht vt l nh nhit si, nhit nng chy, t khi,

tnh tan, ... tng t H C no c cng s nguyn t C v cng b khung C (xem bng 5.2)

Bng 5.2: Hng s vt l ca mt s hirocacbon khng no

CTPT Tn 0nct

0st d

C2H4 Etylen CH2 = CH2 -169 -105 0,566

C3H6 Propen CH3 CH = CH2 -185 -48 0,609

Buten 1: CH2 = CH CH2 CH3 -185 -6 0,630

Trans butan - 2 -106 1 0,660

C4H8 Cis butan - 2 -139 4 0,644

C4H6 Butadien 1,3 -109 -4,5 0,646

Isopren -120 34 0,681

C5H8 Pentadien 1,3 -88 42 0,683



Trang 53

Pentadien 1,4 -148 26 0,659

C2H2 axetylen -82 -84 -

C3H4 Propin -103 -223 -

Butin - 1 -122 8,6 0,650

C4H6 Butin - 2 -24 27 0,694

5.2.3. Tnh cht ho hc

S c mt ca lin kt pi trong phn t lm cho H C khng no c kh nng phn ng cao

hn H- C no. Chnh ni i v ni ba l nhng trung tm phn ng c coi l nhm chc.

5.2.3.1. Phn ng cng H2 trn b mt xc tc kim loi

Nhng phn ng ny ta nhit v ch xy ra khi c cht xc tc nh Ni, Pt, Pd, ...

CH2 CH2 + H2 CH3 CH3

Ni

NiCH CH CH2 CH2 CH3 CH3H2H2

Pb-PbCO3

Ni

H2

CH2 CH CH CH2 + H2 -120c

CH3 CH2 CH CH245%

CH3 CH CH CH248%

CH3 CH2 CH2 CH36%

Ni

5.2.3.2. Phn ng cng electrophin

a) Anken

S phn ng:

+-C C + X+ Y-

X

C C

Y

X Y : H X ; H OH ; HO SO3H; Br Br ; ...

C ch phn ng: c ch AE



Trang 54

+- cham + Y-

X

nhanh

C C + X+ Y -+

C C

+ Y-

X

+C C

X

C C

Y

Hng ca phn ng: Phn ng cng mt tc nhn khng i xng (nh HCl, H2SO4, HOH, ...) vo mot anken

khng i xng s u tin theo hng to thnh cacbocation trung gian bn hn (quy tc

Maccpnhicp). Th d:

CH3 CH CH2 + HBr

CH3 CH CH3

CH3 CH2 CH2(+)

(+) + Br-

+ Br-- Br-

CH3 CH CH3

CH3 CH2 CH2

Br

Br

ben hn

kem ben

95%

5%

Kh nng phn ng ca anken: Khi thay th nguyn t H trong etylen bng nhm y electron (CH3, C2H5, ...) mt

electron ni i s tng ln v cacbocation sinh ra cng bn hn do phn ng cng cng xy

ra d dng hn. Tri li, nhm th ht electron s lm gim mt electron v cacbocation sinh ra

cng km bn, do phn ng cng xy ra kh khn hn. V vy, ta c trnh t v kh nng phn

ng nh sau:

CH2 = CHCOOH < CH2 = CHCl < CH2 = CH2 < CH2 = CHCH3 < CH2 = C(CH3)2

Kh nng phn ng ca HX vo anken: Phn ng cng HX vo anken s d dng nu HX c tnh cht mnh v X(-) c tnh

nucleophin cao. V vy, kh nng phn ng ca HX gim dn theo trnh t:

HI > HBr > HCl > HF

b) Ankin

Phn ng cng: gm hai giai on - Giai on 1: Chuyn ni ba thnh ni i

- Giai on 2: Chuyn ni i thnh ni n

Phn ng cng halogen v HX vo ankin cng tng t phn ng ca anken v c ch

phn ng, hng ca phn ng v nh hng ca nhm th n kh nng phn ng. So vi

anken, th ankin c kh nng phn ng thp hn i cht.



Trang 55

CH3 C CH > CH CH > CH C COOH CH2 = CH2 > CH CH c) Ankaien

Ankaien c th cng halogen v HX to ra hn hp gm sn phm cng 1,2 v cng 1,4.

Tu theo tc nhn phn ng v nhit m mt sn phm no s chim t l cao hn. Th d:

(1,2) Br2

(1,4)

Br Br

20%

80%

400CH2 CH CH CH2

CH2 CH CH CH2

CH2 CH CH CH2

Br Br

5.2.3.3. Phn ng cng ng vng

2000CCH

CH

CH2

CH2

CH2

CH2+

CH2

CH2

CH2

CH2

CH

CH

cis-butadien Etylen Xiclohexen

5.2.3.4. Phn ng trng hp

Trng hp l qu trnh cng hp lin tip nhiu phn t nh ging nhau hay tng t nhau

to thnh phn t c phn t khi ln (cao phn t).

Cht u tham gia trng hp gi l monome, trong phn t monome thng phi c lin

kp. Sn phm thu c l polime cha n mt xch c bn sinh ra t n phn t monome.

Nu n = 2 10 polime c gi l oligome bao gm ime (n=2), trime (n=3), .... n l h s trng hp hay trng hp

a) Anken

Cc anken v dn xut c cng thc chung CH2 = CH R tng i d trng hp iu

kin nhit v p sut nht nh c mt ca cht xc tc, sinh ra polime tng ng. Th d:

TlCl4, Al(C2H5)32-3 at

Etylen

n CH2 CH2 CH2 CH2 n

Polietylen (PE)

CH3

xt, p, toC

Propilen

n CH CH2 CH CH2n

Polipropilen (PP)

CH3



Trang 56

b) Ankaien

Cc ankaien lin hp v n gin nh butadien, isopren, ... c th tham gia phn ng

trng hp to thnh polime dng lm cao su. Th d:

TlCl4, Al(C2H5)32-3 at

nCH2 CH CH CH2Butadien

CH2 CH CH CH2n

Polibutadien

Cis

c) Ankin

- Nh hp

2CH CH CH2 CH C CHCu2Cl2

- Tam hp

3CH CH 6000CC

- a hp

nCH CH

14 hoa hoc huu co (phu).pdf

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