Question

Gabriel synthesis is used for the preparation of:
A. $1{}^\circ $ amine
B. $2{}^\circ $ amine
C. $3{}^\circ $ amine
D. all of the above

Answer 1

Hint: Gabriel synthesis is the chemical reaction that is used for the preparation of the amine from the primary amine. To determine the correct answer we have to write the reaction of the synthesis of the amine.

Complete step by step answer:
- In the given question, we have to choose the correct product which is formed by the Gabriel synthesis.
- Firstly, we have to write the chemical reaction which shows the formation of the amine from the primary alkyl halide.
- The primary alkyl halide is the molecules in which the halide group is attached to the single carbon atom whereas in secondary alkyl halide the halide is attached with the two carbon atoms and in tertiary alkyl halide the halide group is attached to the three carbon atoms.

- Now, the primary alkyl halide will first react with potassium phthalimide which acts as a catalyst and forms ${{\text{C}}_{6}}{{\text{H}}_{4}}{{\text{(CO)}}_{2}}\text{NR}$.
$\text{R - C}{{\text{H}}_{2}}\text{ - Cl + }{{\text{C}}_{6}}{{\text{H}}_{4}}{{\text{(CO)}}_{2}}{{\text{N}}^{-}}{{\text{K}}^{+}}\ \to \text{ }{{\text{C}}_{6}}{{\text{H}}_{4}}{{\text{(CO)}}_{2}}\text{NR}$

- Now, ${{\text{C}}_{6}}{{\text{H}}_{4}}{{\text{(CO)}}_{2}}\text{NR}$ reacts with hydrazine to yield the primary amine by the removal of an alkyl group from ${{\text{C}}_{6}}{{\text{H}}_{4}}{{\text{(CO)}}_{2}}\text{NR}$ and attachment of amine group with an alkyl group and ${{\text{C}}_{6}}{{\text{H}}_{4}}{{\text{(CO)}}_{2}}{{\text{N}}^{-}}$.
${{\text{C}}_{6}}{{\text{H}}_{4}}{{\text{(CO)}}_{2}}\text{NR + N}{{\text{H}}_{2}}\text{N}{{\text{H}}_{2}}\text{ }\to \text{ }{{\text{C}}_{6}}{{\text{H}}_{4}}{{\text{(CO)}}_{2}}{{\text{N}}_{2}}{{\text{H}}_{2}}\text{ + RN}{{\text{H}}_{2}}$

- So, as we can see that amine group is attached to only one carbon atom thus it is a primary amine.
So, the correct answer is “Option A”.

Note: By using the Gabriel synthesis we can yield aromatic amine because the aryl is not able to undergo nucleophilic substitution reaction due to the steric hindrance caused by the aryl group which prevents the action of the upcoming group.