Question

Which one of the following statements is not correct?

• A. The bond angle of $C-O-H$ in methanol is ${108.9}^o$.
• B. Carbon-oxygen bond length in methanol, $C{H}_{3}OH$ is shorter than that of $C-O$ bond length in phenol.
• C. Acid strength of alcohols decreases in the following order: $RC{H}_{2}OH>R_{2}CHOH>R_{3}COH$
• D. Alcohols are weaker acids than water.

Answer 1

Answer: (B)

i) The bond angle is not standard tetrahedral angle because oxygen has two lone pairs on it, which repels carbon and hydrogen and hence decreases the bond angle.

ii) Alcohols are weaker acids than water that can be seen from the $K_a$ values.

iii) Carbon-oxygen bond length in methanol $C{H}_{3}OH$ is longer than that of $C-O$ bond length in phenol because of the resonance occurs in phenol.

iv) As alkyl groups add on, the acidity decreases owing to the $+I$ effect of alkyl groups.

Option C is correct.