Animated Solution for Chemistry - Organic Chemistry: An organic compound (A) (molecular formula $C_6{H}_{12}{O}_2$) was hydrolysed with dil. $H_{2}S{O}_4$ to give a carboxylic acid (B) and an alcohol (C). 'C' gives white turbidity immediately when treated with anhydrous $ZnC{l}_2$ and conc. HCl. The organic compound (A) is

Ester Hydrolysis

The problem presents us with an organic compound A having the molecular formula $C_6{H}_{12}{O}_2$. When this compound is subjected to hydrolysis using dilute $H_{2}S{O}_4$, it breaks down into two distinct products: a carboxylic acid B and an alcohol C.

This specific reaction profile—yielding an acid and an alcohol upon hydrolysis—is the classic signature of an ester. Therefore, we can confidently establish that compound A is an ester.

The Lucas Test

The most revealing piece of information lies in the behavior of alcohol C. The problem states that 'C' produces a white turbidity immediately when treated with a mixture of anhydrous $ZnC{l}_2$ and concentrated HCl.

This reagent mixture is famously known as the Lucas Reagent. The Lucas test is a chemical test used to differentiate between primary, secondary, and tertiary alcohols based on their reactivity with hydrogen halides.

- Primary alcohols do not produce turbidity at room temperature. - Secondary alcohols produce turbidity after about 5 minutes. - Tertiary alcohols react almost instantaneously to form an insoluble alkyl chloride, resulting in immediate white turbidity.

Because alcohol C gives immediate turbidity, it must be a tertiary ($3^{\circ }$) alcohol.

Armed with the knowledge that the ester must yield a tertiary alcohol upon hydrolysis, let's examine the given options. The alcohol portion of an ester is derived from the alkyl group attached to the single-bonded oxygen atom (the $-O-R^{\prime }$ part).

- Option (a): Ethyl butanoate. The alkyl group is ethyl. Hydrolysis yields ethanol, a primary alcohol. - Option (b): tert-Butyl acetate. The alkyl group is tert-butyl. Hydrolysis yields tert-butyl alcohol, which is a tertiary alcohol. - Option (c): Isopropyl propanoate. The alkyl group is isopropyl. Hydrolysis yields isopropyl alcohol, a secondary alcohol. - Option (d): Isobutyl acetate. The alkyl group is isobutyl. Hydrolysis yields isobutyl alcohol, a primary alcohol.

Only the ester in Option (b), tert-butyl acetate, hydrolyses to produce a tertiary alcohol (tert-butyl alcohol). This alcohol perfectly satisfies the condition of giving immediate white turbidity with the Lucas reagent. Thus, compound A is tert-butyl acetate.