Illustrated Glossary of Organic Chemistry

Arndt-Eistert Reaction: A reaction sequence to convert an ester into a homolog having one additional carbon. The new carbon is inserted adjacent to the carboxyl group of the starting carboxylic acid.




Benzoic acid
A carboxylic acid

Benzoyl chloride
An acid chloride

A diazoketone

Phenylacetic acid
A benzoic acid homolog
In this Arndt-Eistert reaction, benzoic acid (PhCO2H) is converted into phenylacetic acid (PhCH2CO2H) by insertion of a methylene group between the benzene ring and carboxyl group of benzoic acid.