How is a Gattermann synthesis different from a Gattermann-Koch synthesis?

A Gattermann synthesis involves the formation of aryl aldehydes, while a Gattermann-Koch synthesis forms aromatic aldehydes from aromatic hydrocarbons.

The Gattermann synthesis, also known as the Gattermann formylation, is a method used in organic chemistry to form aryl aldehydes. This reaction involves the use of a diazonium salt, which reacts with a compound containing an acidic hydrogen atom, such as water, alcohol, or an amine, in the presence of a copper(I) salt. The result is an aryl aldehyde, a type of organic compound that contains a formyl group. This reaction is named after the German chemist Ludwig Gattermann.

On the other hand, the Gattermann-Koch synthesis is a variant of the Gattermann synthesis, which is used to form aromatic aldehydes from aromatic hydrocarbons. In this reaction, the aromatic hydrocarbon reacts with carbon monoxide and hydrochloric acid, in the presence of a Lewis acid such as aluminium chloride or ferric chloride. The result is an aromatic aldehyde, which is a type of organic compound that contains a formyl group attached to an aromatic ring. This reaction is named after Ludwig Gattermann and his student Julius Arnold Koch.

While both reactions are used to form aldehydes, the key difference lies in the starting materials and the type of aldehyde produced. The Gattermann synthesis starts with a diazonium salt and produces aryl aldehydes, while the Gattermann-Koch synthesis starts with an aromatic hydrocarbon and produces aromatic aldehydes. Both reactions are important in the field of organic chemistry, as they provide a method for the synthesis of aldehydes, which are key intermediates in many chemical reactions.