What Is a Thiol Group?

Definition and Examples

This is the chemical structure of cysteine.
This is the chemical structure of cysteine. The yellow SH on the left hand side is a thiol group. Todd Helmenstine
by Anne Marie Helmenstine, Ph.D.
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
Updated May 14, 2018

Definition: A thiol group is a fuctional group containing a sulfur atom bonded to a hydrogen atom. General formula: -SH

Also Known As: sulfanyl group, mercapto group

Examples: The amino acid cysteine contains a thiol group.