Science, Tech, Math › Science Mercaptan Definition Share Flipboard Email Print Bacsica / Getty Images Science Chemistry Basics Chemical Laws 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. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College 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. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated October 03, 2019 Definition: Mercaptan is an organic sulfur compound composed of an alkyl or aryl group and a thiol group.General formula: R-SH where R is an alkyl or aryl group. Also Known As: thiol Examples: The amino acid cysteine is a mercaptan.