What functional group of aspirin causes it to irritate the stomach?

The functional group of the aspirin in which causes this compound to cause a person’s stomach to be irritated is most likely because of the acetyl salicylic acid in which its acid portion of this drug causes the person’s stomach to feel stomach irritation.

The acid (-COOH) functional group of aspirin causes it to irritate the stomach

Explanation:

Aspirin is acetylsalicylic acid with a molecular formula C₉H₈O₈.

It is a cyclic compound composed of a benzene ring along with 2 functional groups: the carboxylic acid (-COOH) and acetyl group (-OCOCH3)

The most common side effect of consuming aspirin is an upset stomach. This is due to the acid functional group which can irritate the stomach lining.