Grapefruit mercaptan is the common name for a natural organic compound found in grapefruit. It is a monoterpenoid that contains a thiol (also known as a mercaptan) functional group. Structurally a hydroxy group of terpineol is replaced by the thiol in grapefruit mercaptan, so it also called thioterpineol.
Grapefruit mercaptan is a derivative of terpineol, containing a thiol functional group. It can also be referred to as thioterpineol.