Question

Write short notes on the following: Coupling reaction:

Hint:

The Gabriel phthalimide synthesis is a useful method for preparing primary amines and avoids the use of toxic reagents like sodium azide.

Answer 1

A coupling reaction is a reaction in which two molecules, usually aromatic compounds, are joined together by the formation of a new carbon-carbon bond. This occurs typically in the presence of a catalyst like iron or copper. A well-known example is the coupling of diazonium salts with phenols or aniline derivatives to form azo compounds: \[ \text{ArN}_2^+ + \text{Ar'-OH} \rightarrow \text{Ar-N=Ar'} + \text{H}_2\text{O} \] This reaction is used in the synthesis of azo dyes. (B) Ammonolysis: Ammonolysis is a chemical reaction in which an amine reacts with a substrate to replace a leaving group (often a halide or ester group) with an amino group (-NH₂). A common example is the reaction of alkyl halides with ammonia: \[ \text{R-Cl} + \text{NH}_3 \rightarrow \text{R-NH}_2 + \text{HCl} \] Ammonolysis reactions are often used in the formation of primary amines. (C) Gabriel phthalimide synthesis: The Gabriel phthalimide synthesis is a method used to prepare primary amines from potassium phthalimide and an alkyl halide. The reaction involves the nucleophilic attack of phthalimide on an alkyl halide, followed by hydrolysis to release the primary amine: \[ \text{C}_6\text{H}_4\text{C(O)N}(\text{C}_2\text{H}_5)\text{K} + \text{R-Cl} \rightarrow \text{R-NH}_2 + \text{C}_6\text{H}_4\text{C(O)N}(\text{C}_2\text{H}_5) + \text{KCl} \] Final Answer: Coupling reactions involve the joining of two molecules to form a new carbon-carbon bond, ammonolysis involves the replacement of a leaving group with an amino group, and the Gabriel phthalimide synthesis is a method for preparing primary amines. Correct Answer: The notes on Coupling reaction, Ammonolysis, and Gabriel phthalimide synthesis are provided above.