Sandmeyer reaction is one of the most important reactions in organic chemistry included in JEE syllabus. It is one of the major reactions for the synthesis of haloarenes. Some FAQs related to Sandmeyer reaction are:
Question: What is Sandmeyer reaction?
Answer: When a primary aromatic amine is treated with sodium nitrite in the presence of cold aqueous mineral acid, a diazonium salt is formed. This freshly prepared diazonium salt is further mixed with cuprous chloride or bromide which results in the replacement of diazonium group by –Cl or –Br. This reaction for the synthesis of haloarenes from a diazonium salt is popularly known as Sandmeyer reaction.
Questions: What is the general mechanism of Sandmeyer reaction?
Answer: The mechanism for the replacement of diazonium group with halogen is found to be radical in nature contrary to being ionic. A general mechanism includes:
Synthesis of diazonium ion:
- Preparation of nitrous acid from sodium nitrite and acid through protonation.
- Formation of nitrogen monoxide cation due to the loss of one equivalent of water from nitrous acid due to protonation.
- The reaction of an aromatic amine with nitrite to form an aryl diazonium salt.
Synthesis of aryl halides:
- The diazonium salt synthesized reacts with copper salt at a temperature of 25-30oC to form the desired aryl halide.
- This reaction is an aradical-nucleophilic aromatic substitution.
Questions: Which reference books can one follow for understanding Sandmeyer reaction?
Answer: For understanding Sandmeyer reaction, one must go through the NCERT class 12th chemistry textbook part-2. A brisk walk through NCERT will give you a sound idea about this reaction. Apart from this, you can follow a reference book to understand the detailed mechanism of this reaction. Some authentic books for understanding the detailed mechanism of Sandmeyer reaction include books from authors like Solomons & Fryhle, Morrison & Boyd. Once you have understood the reaction, you can practice questions from the books of authors like M. S. Chauhan, etc.