Question

In which of the following reactions of alcohol there is no cleavage of C-O bond?

• A. Dehydration reaction of alcohol
• B. Oxidation reaction of alcohol
• C. Reduction reaction of alcohol
• D. Reaction of alcohol with phosphorus tribromide

Answer 1

The correct option is B Oxidation reaction of alcohol

(a) Dehydration of alcohol involves cleavage of $C-O$ bond.
For example: At 433-443 K, Alcohols react with conc. $H_{2}S{O}_4$ to form alkenes.
$C{H}_{3}C{H}_{2}OH\stackrel{\text{Hot conc.}{H}_{2}S{O}_4}{\to }C{H}_2=C{H}_2$

(b) Oxidation of alcohol $3^{\circ }$ alcohols generally do not undergo oxidation however in the presence of $KMn{O}_4$, cleavage of C-C bond takes place to give two acids in which $C-O$ bond remains uncleaved.

(c) Reduction
$C{H}_{3}C{H}_{2}CHO\stackrel{LiAl{H}_4}{\to }C{H}_{3}C{H}_{2}OH$
It involves cleavage of $C-O$ bond.

(d) Reaction with phosphorus tribromide involves cleavage of $C-OH$ bond.
$C{H}_{3}C{H}_{2}OH\stackrel{PB{r}_3}{\to }C{H}_{3}C{H}_{2}Br$

Thus, oxidation reactions of alcohol do not involve cleavage of $C-O$ bond among the given reactions. Hence correct option is (b).