A thiol, also known as a thio alcohol or mercaptan, is an organic compound that has a thiol (–SH) group bound to a carbon atom. Thiols (general formula RSH) are the sulfur analogs of alcohols. They have unpleasant odors resembling rotten cabbage or garlic. Ethane thiol is a typical thiol, having the formula C2H5SH.


Thiols are prepared by excess NaSH of H2S on RX, sulfur on Grignard reagents, of hydrolysis of thiol esters RSC(O)R1. Thiols are readily oxidized to disulfides RSSR and substituted to sulfides RSR1.