Question

2-butanol is converted into 2-methylbutanoic acid by:
A. (i) Cu (ii) HCN (iii) $H_3{O}^{+}$
B. (i) HCN (ii) $H_3{O}^{+}$
C. (i) $PC{l}_5$ (ii) KCN (iii) $H_3{O}^{+}$
D. (i) KCN (ii) $H_3{O}^{+}$

Answer 1

Hint: Butanol is a molecule containing 4 carbon atoms along with an alcoholic group that’s why the suffix ol is attached with it. While butanoic acid is those compounds in which an acidic group is present.

Complete answer:
Butanol is primarily used as a solvent and as an intermediate in chemical synthesis and also used as a fuel. 2-butanol describes the position of alcoholic group i.e. OH group is present on 2nd carbon atom which can be shown as:

2-methylbutanoic acid tells that a 2nd carbon methyl group is attached and an acidic group is present on the first position. It exists in two enantiomeric forms which are defined as (R) and (S)-2-methylbutanoic acid. (R)-2-methylbutanoic acid occurs naturally in cocoa beans and (S)-2-methylbutanoic is present in many fruits such as apples and apricots.

2-butanol is converted into 2-methylbutanoic acid step by step:
Ist step converts 2-butanol to 2-chlorobutane

In second step, 2-chlorobutane reacts with KCN and get Cl group get replaced with CN group which can be shown as:

In third step, it reacts with $H_3{O}^{+}$and get converted into 2-methylbutanoic acid which can be shown as:

Thus we can say that option C is the correct answer.

Note:
2-methylbutanoic acid is a slightly volatile, colorless liquid with a pungent cheesy odor. The smell differs significantly between the two enantiomeric forms i.e. (S)-2-Methylbutyric acid has a pleasantly sweet, fruity odor while (R)-2-methylbutanoic acid has a cheesy, sweaty odor. The main use of the materials and their esters used as flavours and food additives.