Which of the following reaction(s) can be used for the preparation of alkyl halides? (I) CH3CH2OH + HCl Anh. ZnCl2 (II) CH3CH2OH + HCl Anh. ZnCl2 (III) (CH3)3COH + HCl Anh. ZnCl2 (IV) (CH3)2CHOH + HCl Anh. ZnCl2
- (I) and (II) only
- (IV) only
- (III) and (IV) only
- (I), (III) and (IV) only
Answer
(4) (I), (III) and (IV) only
Solution
As per NCERT, primary and secondary alcohols react with HCl only in the presence of anhydrous ZnCl2 (Groove's process), whereas tertiary alcohols react readily with concentrated HCl at room temperature without a catalyst.
(I) 1° alcohol + HCl / anhyd. ZnCl2 ⇒ CH3CH2Cl ✓
(II) 1° alcohol + HCl without ZnCl2 ⇒ no appreciable reaction ✗
(III) 3° alcohol + HCl ⇒ (CH3)3CCl ✓
(IV) 2° alcohol + HCl / anhyd. ZnCl2 ⇒ (CH3)2CHCl ✓
∴ (I), (III) and (IV) can be used.
Answer: (4)