Remember that Hofmann Bromamide Degradation always reduces the carbon chain length by one. Count the carbons in the reactant and options to quickly eliminate incorrect structures.
Step 1: Understanding the Concept:
This is a multi-step organic transformation involving acid chloride conversion to an amide, followed by Hofmann bromamide degradation, diazotization, and finally hydrolysis to form an alcohol. Step 2: Detailed Explanation:
The starting material is 4-methylpentanoyl chloride: \(CH_3 - CH(CH_3) - CH_2 - CH_2 - COCl\).
(i) Reaction with alcoholic \(NH_3\):
The acid chloride reacts with ammonia to form an amide.
\[ CH_3 - CH(CH_3) - CH_2 - CH_2 - COCl \xrightarrow{NH_3} CH_3 - CH(CH_3) - CH_2 - CH_2 - CONH_2 \]
The product is 4-methylpentanamide (6 carbons).
(ii) Reaction with \(Br_2 / NaOH\) (Hofmann Bromamide Degradation):
The amide is converted into a primary amine with one less carbon atom. The carbonyl carbon is lost as \(CO_3^{2-}\).
\[ CH_3 - CH(CH_3) - CH_2 - CH_2 - CONH_2 \xrightarrow{Br_2, NaOH} CH_3 - CH(CH_3) - CH_2 - CH_2 - NH_2 \]
The product is 3-methylbutan-1-amine (5 carbons).
(iii) & (iv) Reaction with \(NaNO_2 / HCl\) and \(H_2O\):
Primary aliphatic amines react with nitrous acid (formed in situ) to form an unstable diazonium salt, which decomposes to form a carbocation. This carbocation reacts with water to form the corresponding alcohol.
\[ CH_3 - CH(CH_3) - CH_2 - CH_2 - NH_2 \xrightarrow{NaNO_2, HCl} [CH_3 - CH(CH_3) - CH_2 - CH_2 - N_2^+] \xrightarrow{-N_2} \] \[CH_3 - CH(CH_3) - CH_2 - CH_2^+ \]
\[ CH_3 - CH(CH_3) - CH_2 - CH_2^+ \xrightarrow{H_2O} CH_3 - CH(CH_3) - CH_2 - CH_2 - OH \]
The major product is 3-methylbutan-1-ol. Step 3: Final Answer:
The product has 5 carbons and a terminal hydroxyl group, which matches Option (A).
