Sulphonation

Sulphonation is a chemical process in which a sulphonic acid group (SO3H) is introduced onto an organic molecule. This reaction is typically carried out using a sulphur trioxide (SO3) source, such as fuming sulphuric acid or chlorosulphonic acid, in the presence of a catalyst. The process is commonly used in the production of dyes, detergents, and pharmaceuticals.

The sulphonation reaction can occur through two main mechanisms: electrophilic aromatic substitution and nucleophilic aromatic substitution. In electrophilic aromatic substitution, the sulphur trioxide acts as an electrophile, attacking the aromatic ring of the substrate. This mechanism is often used for the sulphonation of aromatic compounds. In nucleophilic aromatic substitution, the sulphur trioxide reacts with a nucleophile, such as an alcohol or amine, to form a sulphonate ester. This mechanism is less common but can be useful for the sulphonation of less reactive substrates.

Sulphonation is a versatile reaction that can be used to introduce a wide range of functional groups onto organic molecules. The resulting sulphonate groups can be further modified or used as handles for subsequent reactions. The process is typically carried out under mild conditions and can be scaled up for industrial applications. However, the use of sulphur trioxide and its derivatives can be hazardous, and appropriate safety measures must be taken when handling these reagents.