CBSE Class 12 Chemistry 2014 Delhi Set 1 Solved Paper

Question : 30

Total: 30

(a) Write the products of the following reactions:

(i)

(ii) 2C6H5‌CHO+ Conc. NaOH‌───▸
(iii) CH3‌COOH‌

Cl2∕P

───▸

OR
(a) Account for the following:
(i) CH3‌CHO is more reactive than CH3COCH3 towards reaction with HCN.
(ii) Carboxylic acid is a stronger acid than phenol.
(b) Write the chemical equations to illustrate the following name reactions:
(i) Wolff-Kishner reduction
(ii) Aldol condesnation
(iii) Cannizzaro reaction

Solution:

(a) (i)

(ii)

C6H5−CHO

Benzaldehyde

+ conc. NaOH‌───▸

C6H5‌COONa

Sodium‌benzoate

(iii) CH3−COOH‌

Cl2∕P

→

‌Cl−CH2−COOH +HCl
OR(a) (i) In acetone alkyl chain is present on both side of carbonyl group that cause steric hinderance and make them less reactive towards nucleophilic attack because both alkyl group shows the -I effect while all this not occur in acetaldehyde which make it more reactive towards the nucleophilic attack.
(ii) Carboxylic acid is more acidic because of its stabilising resonating structure which make carboxylate ions. Carboxylic acid have two oxygen atoms which are highly electronegative in nature and while in phenols acidic character is due to presence of phenoxide ions means one oxygen atom is present in the structure.
(b) (i) Wolff-Kishner Reduction:

(ii) Aldol condensation: Aldehydes and ketones having at least one α-hydrogen react in the presence of dilute alkali to form β-hydroxy aldehydes (aldol) or β-hydroxyl ketones (Ketol).

(iii) Cannizaro reaction:

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