Ncert Exercises & Solutions

The increasing order of reduction of alkyl halides with zinc and dilute HCl is

1. $R - Cl < R - I < R - Br$

2. $R - Cl < R - Br < R - I$

3. $R - I < R - Br < R - Cl$

4. $R - Br < R - I < R - Cl$

HINT: Weaker bond of halogen with carbon gets easily reduced.

EXPLANATION (2).

The reactivity of halogens with alkane is

F_{2} > {Cl}_{2} > {Br}_{2} > I_{2}

. Hence, reduction of alkyl halide with Zn and dilute HCl follows reverse order i.e.,

R - I > R - Br > R - Cl

. Further, the reactivity of this reduction increases as the strength of C-X bond decreases.