Question

Which from following statements is NOT correct regarding Hofmann's exhaustive alkylation?

• A. In this quaternary ammmonium salts are obtained.
• B. Two moles of alkylhalide when heated with one mole primary amine forms tetraalkyl ammonium halide.
• C. Depending on the quantity of alkyl halides treated with primary amine, the mixture of secondary and tertiary amines obtained.
• D. The reaction is carried out in presence of \(\text{NaHCO}_3\)

Hint:

Count how many alkyl groups a primary amine needs to become a quaternary salt.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
In Hofmann exhaustive alkylation, an amine is treated with excess alkyl halide so that all N-H hydrogens are replaced by alkyl groups, giving a quaternary ammonium salt. A base such as \(\text{NaHCO}_3\) is used to take up the acid formed.

Step 2: Key Formula or Approach:
A primary amine, \(\text{RNH}_2\), already has one alkyl group. A quaternary ammonium ion has four, so three more are needed, which means three moles of alkyl halide.

Step 3: Detailed Explanation:
Statement A: the final products are quaternary ammonium salts. This is correct.
Statement B: two moles of alkyl halide only add two alkyl groups, giving a tertiary amine, \(\text{R-NR}'_2\) (as its salt) and not a tetraalkyl ammonium halide. So B is NOT correct.
Statement C: with a limited amount of alkyl halide the product is a mixture of secondary and tertiary amines. This agrees with the textbook description.
Statement D: the reaction uses \(\text{NaHCO}_3\) as the base. This is correct.

Final Answer:
Statement B is the incorrect one, option (B). \[ \boxed{\text{B}} \]