tert-Butylthiol, also known as tert-butyl mercaptan (TBM), and abbreviated t-BuSH, is an organosulfur compound with the formula . This thiol has a strong odor. It is considered a flavoring agent.
tert-Butylthiol was first prepared in 1890 by Leonard Dobbin by the reaction of zinc sulfide and t-butyl chloride.
The compound was later prepared by the reaction of the Grignard reagent, t-BuMgCl, with sulfur to give the corresponding thiolate, followed by hydrolysis. This preparation is shown below:
It is made industrially by the reaction of isobutylene with hydrogen sulfide over a clay (silica alumina) catalyst.
tert-Butylthiol is deprotonated by lithium hydride in an aprotic solvent such as hexamethylphosphoramide (HMPA). The resulting lithium thiolate salt has been used as demethylating reagent. For example, treatment with 7-methylguanosine gives guanosine. Other N-methylated nucleosides in tRNA are not demethylated by this reagent.
tert-Butylthiol reacts with thallium(I) ethoxide to give the thallium thiolate:
This thallium thiolate can be used to convert acyl chlorides to the thioester:
reacts with with to give the tetrathiolate complex:
tert-Butylthiol is the main ingredient in many gas odorant blends. It is always utilized as a blend of other compounds, typically dimethyl sulfide, methyl ethyl sulfide, tetrahydrothiophene or other mercaptans such as isopropyl mercaptan, sec-butyl mercaptan and/or n-butyl mercaptan, due to its rather high melting point of . These blends are used only with natural gas and not propane, as the boiling points of these blends and propane are quite different. Because propane is delivered as a liquid and vaporizes to gas when it is delivered to the appliance, the vapor liquid equilibrium would substantially reduce the amount of odorant blend in the vapor.
tert-Butylthiol had been listed on the European Food Safety Authority (FL-no: 12.174) as a flavor additive. There is no indication of what flavor(s) it may have been used in. It has been removed from this list.
tert-Butylthiol is a very minor component of cooked potatoes.
The threshold limit value (TLV) is 0.5 ppm. tert-butylthiol has an odor threshold of <0.33 ppb.