1) wolff kishner reduction reaction.
2) clemmensen reduction
3) gattermann koch
4) stephen Reaction
5) kolbe's reaction
6) Perkins reaction
with example
Answers
Answer:
) Write the chemical reaction involved in Wolff-Kishner reduction.
(b) Arrange the following in the increasing order of their reactivity towards nucleophilic addition reaction:
C
6
H
5
COCH
3
,CH
3
−CHO,CH
3
COCH
3
(c) Why carboxylic acid does not give reactions of carbonyl group?
(d) Write the product in the following reaction
CH
3
CH
2
CH=CH−CH
2
CN
1.(i−Bu)
2
AlH
2.H
2
O
(e) A and B are two functional isomers of compound C
3
H
6
O.On heating with NaOH and I
2
, isomer B forms yellow precipitate of iodoform whereas isomer A does not form any precipitate. Write the formulae of A and B.
Explanation:
a) In Wolff-Kishner reduction carbonyl group of aldehydes and ketones is converted into methylene group. Aldehydes or ketones are heated with hydrazine and KOH or ptoassium tert butoxide in ethylene glycol to forms alkanes.
R−C(O)−R
′
(i)H
2
N−NH
2
,H
2
O
(ii)KOH/ethylene glycol,Δ
R−CH
2
−R
′
+N
2
(b) C
6
H
5
COCH
3
<CH
3
COCH
3
<CH
3
−CHO
In general, aldehydes are more reactive than ketones.
The aromatic aldehydes and ketones are less reactive than aliphatic counterparts.
(c) The lone pair of electrons on O atom of -OH group of carboxylic acid is in resonance with carbonyl group. Hence, the carbonyl carbon of carboxylic acid is less electrophilic than the carbonyl carbon of aldehydes or ketones.
Hence, carboxylic acid does not give reactions of carbonyl group.
(d) DIBAL-H reduces nitriles to aldehydes.
CH
3
CH
2
CH=CH−CH
2
CN
1.(i−Bu)
2
AlH
2.H
2
O
CH
3
CH
2
CH=CH−CH
2
CHO
(e) B forms yellow precipitate of iodoform.
Hence, B is a methyl ketone as it undergoes haloform reaction.
Thus, B is acetone CH
3
COCH
3
The isomer A does not form any precipitate.
Hence, it is not a methyl ketone. Hence A is propanal CH
3
CH
2
CHO