(a) Give reasons :

(i) Benzoic zcid is a stronger acid than acetic acid.

(ii) Methanal is more reactive towards nucleophilic addition reaction than ethanal.

(b) Give a simple chemical test to distinguish between propanal and propanone.

 

 

 

 

 
 
 
 
 

Answers (1)
S Sumit

(a)

(i) Benzoic acid is stronger acid than acetic acid because the conjugate base formed after losing H^+, is resonance stabilised in case of benzoic acid.

                                 (Resonance stabilised)

 

(ii) It is due to steric and electronic reasons. Presence of methyl groupin ethanol,  hinders the approach of nucleophile to carbon of  and it also reduces the electrophilicity of the carbonyl gp. due to +I effect.

(b) Fehling's TestCH_3CH_2CHO+\left [ Ag(NH_3)_2 \right ]^++OH^-\overset{\bigtriangleup }{\rightarrow}CH_3CH_2COO^-+Ag\downarrow +NH_3+H_2O

The silver thus deposited shines like a mirror. 

Propanone does not show fehling's test.

 

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