. Illustrate the following name reactions


(a) Illustrate the following name reactions:

(i) Cannizzaro’s reaction

(ii) Clemmensen reduction

(b) How would you obtain the following:

(i) But-2-enal from ethanal

(ii) Butanoic acid from butanol

(iii) Benzoic acid from ethylbenzene

                                                           OR

(a) Give chemical tests to distinguish between the following:

(i) Benzoic acid and ethyl benzoate

(ii) Benzaldehyde and acetophenone.

(b) Complete each synthesis by giving missing reagents or products in the following

synthesis

Best Answer

(a) (i) Cannizzaro reaction: Aldehydes which do not have an a-hydrogen atom undergoes disproportionation reactions on treatment with concentrated alkali to give a mixture of carboxylic acid salt and alcohol

Cannizzaro reaction

(ii) Clemmensen reduction: The carbonyl group of aldehydes and ketones is reduced to CH2 group on treatment with zinc-amalgam and concentrated hydrochloric acid

Clemmensen reduction

obtain

(a) (i) Benzoic acid on warming with sodium hydrogen carbonate gives brisk effervescence of CO2 gas while ethyl benzoate does not respond to this test

Benzoic acid

 

(ii) Benzaldehyde and acetophenone

Iodoform test: Acetophenone being a methyl ketone on treatment with I2 /NaOH undergoes Iodoform reaction to give yellow ppt. of iodoform but benzaldehyde does not

synthesis

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