Aldehydes and Ketones

醛、酮化學反應與檢驗

有機化學實驗有機化學實驗有機化學實驗有機化學實驗

1. Aldehydes and ketones:

aldehydes ketones

reactivity:>

原 理

RC

O

H RC

O

R'

(1) Oxidation & Reduction:

OH

HO

OO

R

OH

[Red] [Oxid]

Reaction of Carbonyl Group:

(2) Protonation:

O + H+

O H+

Nu

O H+

Reaction of Carbonyl Group:

(3) Condensation of aldehyde (ketone) and alcohol:

( Ketone → Hemiketal → Ketal ) 可當醛可當醛可當醛可當醛、、、、酮的保護基酮的保護基酮的保護基酮的保護基加入加入加入加入鹽酸鹽酸鹽酸鹽酸水解可復原回原來的醛基或酮基水解可復原回原來的醛基或酮基水解可復原回原來的醛基或酮基水解可復原回原來的醛基或酮基

RC

O

HH O R'+ R C

O

O R'

HH

R C

OH

O R'

H Hemiacetal

H O R'R C

OR'

O R'

H Acetal

Reaction of Carbonyl Group:

(4) Bisulfite addition: ( 工業界純化醛的方法工業界純化醛的方法工業界純化醛的方法工業界純化醛的方法)

RC

HO + NaHSO3 R C SO3H

H

ONa

R C SO3Na

H

OH

water-solube

HClAldehyde

Reaction of Carbonyl Group:

(5) Reaction with amine: (imine or Schiff base)

C

O

H

HCl

pH=4.5~6.5 C

O

H

H

CH3NH2

H3C C

H

OH

NH2CH3-H - H2O

+ H3CC

HN

CH3imine

Reaction of Carbonyl Group:

(6) 2,4-dinitrophenylhydrazones

RC

R'O + NO2

H

NH2N

O2N

NO2

O2N

N

H

NR'

CR

Reaction of Carbonyl Group:

2. reaction of carbonyl group:

(7) Tollen’s Reagent:(identification for aldehyde and ketones)

Aldehydes and Ketones

Ag+(NH3)2OH-2 + R C H

O

Ag2 + + +R C O-

ONH4

+

H2O NH33

(8) Iodoform Test: (identification of methyl ketone)

Reaction of Carbonyl Group:

R C CH3

O

+ OH-R C CH2

-

O

+ H2OI2

R C CH2I

OI2 I2OH-OH-

R C CI3

OOH-

R C O-

O

+ HCI3 yellow solid: Iodoform

positive for R C CH3

H

OH

H3C CH2OH H3C C H

O

, ,

(1) Identification of carbonyl group with 2,4-DNP:

Reagent :3g 2,4-DNP + 15mL conc. H 2SO4 + 20mL H2O (ice bath) + 70mL 95% EtOH → stir → filter

Procedures :1 or 2 drops sample + 1mL Methanol + 0.5mL 2,4-DNP reagent ↓

shake vigorously↓

if no ppt, stand for 15 min

步 驟

RC

R'O + NO2

H

NH2N

O2N

NO2

O2N

N

H

NR'

CR

Notes : Products (2,4-dinitrophenylhydrazone):

yellow → aldehydes or ketones in which the carbonyl group is not conjugated with another functional group

Ex:

Ex:

orange-red → aldehydes or ketones in which the carbonyl group is conjugated with C=C or with benzene ring

步 驟

O

O

H

O

(2) Iodoform test: (identification of methyl ketone )

Reagent : 20g KI + 10g I 2 + 80mL H2O → ~90mL KI 3(aq)

stirring until solution is complete(This solution is deep brown due to the I 3

- )

步 驟

R C CH3

O

+ OH-R C CH2

-

O

+ H2OI2

R C CH2I

OI2 I2OH-OH-

R C CI3

OOH-

R C O-

O

+ HCI3 yellow solid: Iodoform

2 drops sample + 1mL 1,4-dioxane + 1mL 10%NaOH (aq)

↓add KIKIKIKI3(aq)3(aq)3(aq)3(aq) and shake until a slight excess yields a definite dark color of iodine↓water bath at temp.=60 ℃↓If the solution becomes colorless, continue adding KIKIKIKI3(aq)3(aq)3(aq)3(aq)

and shake (until the dark color of iodine no change for 2 min )↓fill the test tube with H 2O and allow to stand for 15 min↓

Result: produced the yellow ppt (iodoform m.p 119~ 121℃)

步 驟

結 果

SamplesSamplesSamplesSamples StructuresStructuresStructuresStructures 2,42,42,42,4----DNPDNPDNPDNP Iodoform testIodoform testIodoform testIodoform test Silver mirrorSilver mirrorSilver mirrorSilver mirror

AcetoneAcetoneAcetoneAcetone ＋＋＋＋ ＋＋＋＋ －－－－

BenzaldehydeBenzaldehydeBenzaldehydeBenzaldehyde ＋＋＋＋ －－－－ ＋＋＋＋

BenzophenoneBenzophenoneBenzophenoneBenzophenone ＋＋＋＋ －－－－ －－－－

EthanolEthanolEthanolEthanol －－－－ ＋＋＋＋ －－－－

Unknown 1Unknown 1Unknown 1Unknown 1

Unknown 2Unknown 2Unknown 2Unknown 2

Unknown 3Unknown 3Unknown 3Unknown 3

CH

O

C

O

H3CC

OH

H H

H3CC CH3

O

Homework

(1) 實驗中實驗中實驗中實驗中, unknown 1 的分子式為的分子式為的分子式為的分子式為C6H10O,H1-NMR光譜如下光譜如下光譜如下光譜如下,試問其結構式為何試問其結構式為何試問其結構式為何試問其結構式為何?

11 10 9 8 7 6 5 4 3 2 1 00

5

10

Homework

(2) 實驗中實驗中實驗中實驗中, unknown 2 的分子式為的分子式為的分子式為的分子式為C3H8O,試問其結構式為何試問其結構式為何試問其結構式為何試問其結構式為何?

Homework

(3) 實驗中實驗中實驗中實驗中, unknown 3 的分子式為的分子式為的分子式為的分子式為C8H8O,H1-NMR光譜如下光譜如下光譜如下光譜如下, 試問其結構式為何試問其結構式為何試問其結構式為何試問其結構式為何?

10 5 00

5

Check out

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2. 檢查過後請將廢液倒到檢查過後請將廢液倒到檢查過後請將廢液倒到檢查過後請將廢液倒到””””含鹵素含鹵素含鹵素含鹵素””””有機廢液桶有機廢液桶有機廢液桶有機廢液桶。。。。

3. 試管需清洗乾淨試管需清洗乾淨試管需清洗乾淨試管需清洗乾淨,置於各組共用器材櫃置於各組共用器材櫃置於各組共用器材櫃置於各組共用器材櫃。。。。

4. 評分後評分後評分後評分後,鑰匙交回方可離開鑰匙交回方可離開鑰匙交回方可離開鑰匙交回方可離開。。。。