What is produced when benzene undergoes ozonolysis?

Ozonolysis is an oxidation reaction in which an organic compound containing double or multiple bonds reacts with ozone (O₃) to form smaller oxygenated products such as aldehydes, ketones, or acids. When benzene (C₆H₆) undergoes ozonolysis, it reacts with ozone to form an unstable ozonide intermediate, which upon hydrolysis produces glyoxal (OHC–CHO) molecules.

Benzene is an aromatic compound consisting of a six-membered carbon ring with alternating double bonds. During ozonolysis, ozone attacks these π bonds, breaking the ring structure completely. Each carbon-carbon double bond is cleaved, resulting in the formation of three molecules of glyoxal, which is the simplest dialdehyde.

The reaction can be represented as:

C6H6+3O3→3OHC–CHOC_6H_6 + 3O_3 → 3OHC–CHOC6H6+3O3→3OHC–CHO

This reaction demonstrates that ozonolysis of aromatic rings leads to oxidative cleavage, converting the stable aromatic structure into open-chain aldehyde or carboxylic compounds, depending on reaction conditions. In the case of benzene, mild hydrolysis yields glyoxal, whereas stronger oxidative conditions can further oxidize the product to oxalic acid.

It is important to note that compounds like glycol and vicinal diols are produced when alkenes undergo ozonolysis followed by reduction or hydration, not in the case of benzene. The aromatic stability of benzene is lost during ozonolysis, and the ring-opening results exclusively in glyoxal formation under typical reaction conditions.

Understanding ozonolysis is essential in organic chemistry because it helps determine the position of double bonds in unknown compounds and provides insight into reaction mechanisms involving oxidation and ring cleavage in hydrocarbons