Download - 5racemat
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Racemat (racemska modifikacija, racemski oblik)
-smesa ekvimolarnih količina (+) i (-) enantiomera. Racemska modifikacija ne skreće ravan polarizovanog svetla. Obeležava se sa (+) ili (RS) (ranije dl)
Tri vrste racemskih modifikacija u čvrstom stanju:1. Konglomerat, kristal građen samo od jednog enantiomera2. Racemsko jedinjenje kristal građen od oba enantiomera 1:1 3. Čvrst racemski rastvor oba enantiomera nasumično
raspoređena u kristalu
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Prepoznavanje vrste čvrstih racemataa. Konglomerat
b. Racemsko jedinjenje
T T
sastav50%100% d 100% l
T T
sastav50%100% d 100% l
a. b.
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Kvaziracemat
CH2COOH
BrH
COOH
CH2COOH
Cl H
COOH
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Dobijanje racemata
a. Mešanje (+) i (-) enantiomera
b. Sinteza
c. Racemizacija
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Racemizacija
a
b
c
d
b
a
b
c
d
(S)-enantiomer (R)-enantiomer
intermedijer iliprelazno stanje b
a
cd
a
cd
a
c
d
a
c
d
(S)-karbanjon (R)-karbanjona
cd
a. b. c.
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a
b
c
d
b-
a
b
c
d
(S)-enantiomer (R)-enantiomer
b-
a
cd
b b
prelazno stanje
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Kiselinom ili bazom katalizovana racemizacija kod jedinjenja koja poseduju kiselu C-H vezu na hiralnom C-atomu
enolni oblik(planaran)
H+
H
EtMe
C6H5
O
OH
C6H5Me
EtEt
HMe
C6H5
O
EtMe
C6H5
OO
C6H5Me
Et. . -
enolatni anjon(planaran)
B-
S-enantiomer R-enantiomer
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Rezolucija (razlaganje racemata)
(+)
(+)
(-)
(-)
a. Razlaganje mehaničkim putem
b. Razlaganje biohemijskim metodama
c. Razlaganje preko diastereoizomera
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Biohemijska metoda rezolucije
COO-
RNH2
H
COO-
RH2NH
COO-
RNH2
H
C NH
-OOC
R
D-aminooksidaza
D-enantiomer
L-enantiomer
racemat
L-enantiomer
+
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Frakciono razdvajanje dijastereoizomera
+_ -Aracemat
+ (+)-R (+)-A-(+)-R + (-)-A-(+)-R
dijastereoizomeri
odvajanje frakcionomdestilacijom ili kristalizacijom
(+)-A-(+)-R (-)-A-(+)-Rčist dijasteroizomer čist dijasteroizomer
regeneracija regeneracija
(+)-A + (+)-R (-)-A + (+)-Rčist (+)-enantiomer čist (-)-enantiomer
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Asimetrična transformacija prvog i drugog reda
(+)-A (-)-A(+)-R
(+)-A-(+)-R (-)-A-(+)-R
(-)-A-(+)-R
regeneracija
(-)-A + (+)-R100% (-)-enantiomer
taloži se samo jedandijastereoizomer
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Razlaganje racemata na hiralnoj stacionarnoj fazi
(R,S)eluent
R
SR
S
S
R
R
hiralni adsorbent
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Razlaganje racemata kinetičkom metodom
+_ -Aracemat
+ (+)-R(+)-A-(+)-R + (-)-A-(+)-R
dijastereoizomeru višku
odvajanje frakcionomdestilacijom ili kristalizacijom
(+)-A-(+)-R (-)-A-(+)-Rčist dijasteroizomer čist dijasteroizomer u višku
regeneracija regeneracija
(+)-A + (+)-R (-)-A + (+)-R
čist (+)-enantiomer čist (-)-enantiomer u višku
reakcija sezaustavipre kraja