Answer: Potassium phthalimide is used; after SN2 alkylation and hydrazinolysis, only primary amines form because the phthalimide N can only be monoalkylated.
- A Potassium phthalimide is used; after SN2 alkylation and hydrazinolysis, only primary amines form because the phthalimide N can only be monoalkylated
- B The whole synthesis is mechanistically restricted to working mainly with primary alkyl halide substrates as frequently observed in practice in many documented cases
- C The intermediate's acidic hydrolysis happens to fortuitously halt precisely at the primary amine stage according to conventional understanding
- D The Gabriel synthesis is said to work mainly for preparing aromatic primary amines instead in routine practice overall in most cases under typical conditions
Correct answer: A. Potassium phthalimide is used; after SN2 alkylation and hydrazinolysis, only primary amines form because the phthalimide N can only be monoalkylated
Explanation: In Gabriel synthesis, potassium phthalimide (N has only one active H equivalent) undergoes SN2 with an alkyl halide. After hydrazinolysis (or acid hydrolysis), only a primary amine (RNH₂) is obtained; no secondary or tertiary amines are possible.
SN2 proceeds in a single step with backside attack and inversion of configuration, while SN1 forms a planar carbocation intermediate first, leading to racemisation.
Concept context
Study carbon-halogen compounds: how they are made, how they react via SN1/SN2 and elimination, their stereochemistry, and their environmental impact.