. Give simple chemical tests to distinguish between the following


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

(i) Propanal and propanone

(ii) Benzaldehyde and acetophenone

(b) How would you obtain

(i) But-2-enal from ethanal?

(ii) Butanoic acid from butanol?

(iii) Benzoic acid from ethylbenzene?

OR

(a) Describe the following reactions giving a chemical equation in each case:

(i) Cannizzaro’s reaction

(ii) Decarboxylation reaction

(b) Complete the following chemical equations

chemical equations

Best Answer

(a) (i) Propanal and propanone

Tollen’s reagent test: Propanal being an aldehyde reduces Tollen’s reagent to silver mirror but propanone being a ketone does not.

Tollen’s reagent test

(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.

Iodoform test

(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) Decarboxylation: Carboxylic acids lose carbon dioxide to form hydrocarbons when their sodium salts are heated with sodalime.

Decarboxylation

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