What is the most suitable temperature for the diazotisation reaction to take place?

0°C

The correct answer is option 1. 0°C.

Diazotization reactions involve the conversion of aromatic primary amines to diazonium salts by treatment with nitrous acid \((HNO_2)\) or a nitrite salt \((NaNO_2)\) under acidic conditions. These reactions are crucial in organic synthesis for introducing diazonium groups onto aromatic compounds, which can then undergo various substitution reactions to form a wide range of organic products, such as azo dyes.

The most suitable temperature for diazotization reactions is typically in the range of 0°C to 5°C. Here's why:

Control of Reaction Rate: Diazotization reactions are highly exothermic, meaning they release a significant amount of heat as they proceed. Performing the reaction at low temperatures helps to slow down the rate of reaction, preventing it from proceeding too quickly and potentially leading to uncontrolled reactions or even explosions. By controlling the reaction rate, it's easier to manage the reaction conditions and ensure a successful outcome.

Minimization of Side Reactions: At higher temperatures, the diazonium salt formed during the reaction can undergo unwanted side reactions or decomposition, leading to the formation of undesired by-products. Performing the reaction at low temperatures minimizes these side reactions, enhancing the selectivity of the reaction and increasing the yield of the desired product.

Prevention of Decomposition: Diazonium salts are relatively unstable compounds that can decompose under certain conditions, especially at elevated temperatures. Cooling the reaction mixture helps to stabilize the diazonium salt and prevent its decomposition during the reaction.

Improved Safety: Performing diazotization reactions at low temperatures improves safety by reducing the risk of accidents or hazardous situations associated with highly exothermic reactions. It minimizes the potential for overheating and helps to maintain a controlled environment in the laboratory.

In summary, the most suitable temperature for diazotization reactions is typically around 0°C to 5°C. Operating at these low temperatures allows for better control of the reaction rate, minimization of side reactions, prevention of decomposition, and improved safety, ultimately leading to higher yields and better quality products.