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Friedel-Crafts Acylation and Cyanohydrins
Concepts tested here
- Multi-step synthesis from acetic acid
All Questions
2005 AIPMT 1 question
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In a set of reactions acetic acid yielded a product D
$CH_3COOH \xrightarrow{SOCl_2} A \xrightarrow[\text{Anhy. }AlCl_3]{\text{Benzene}} B \xrightarrow{HCN} C \xrightarrow{H_2O} D$
The structure of D would be -Step 1: $CH_3COOH \xrightarrow{SOCl_2} CH_3COCl$ (A, acetyl chloride) $+ SO_2 + HCl$
Step 2: Friedel-Crafts acylation: $C_6H_6 + CH_3COCl \xrightarrow{\text{anhy. }AlCl_3} C_6H_5COCH_3$ (B, acetophenone) $+ HCl$
Step 3: HCN adds to the carbonyl group of acetophenone to form a cyanohydrin: $C_6H_5COCH_3 + HCN \rightarrow C_6H_5-C(OH)(CN)-CH_3$ (C)
Step 4: hydrolysis of the cyano group gives a carboxylic acid: $C_6H_5-C(OH)(CN)-CH_3 \xrightarrow{H_2O/H^+} C_6H_5-C(OH)(CH_3)-COOH$ (D)
D is 2-hydroxy-2-phenylpropanoic acid (atrolactic acid).
So the structure of D is $C_6H_5-C(OH)(CH_3)-COOH$.