Science, Tech, Math › Science What Is a Thiol Group? Definition and Examples Share Flipboard Email Print This is the chemical structure of cysteine. The yellow SH on the left hand side is a thiol group. Todd Helmenstine Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry in Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate by Anne Marie Helmenstine, Ph.D. 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. Continue Reading