Thiols

THIOLS

Figure 94.

Much of the chemistry of thiols and related compounds can be predicted from a knowledge of their oxygen-containing analogues. The SH group can be called a sulfhydryl group or a mercapto group. Sulfides, as you’ll remember have the RSR’ configuration, while the disulfide compound is referred to as the RSSR’ molecule. The sulfate ion goes by the chemical name of SO4(two minus), while thiosulfate is the S2O3 (two-minus). The thiolate anion is the RS- anion, similar to the alkoxy- anion. The trialkylsulfonium ion is referred to as R3S+ anion, similar to the hydronium ion (H3O+) ion as shown in figure 94:

Figure 95.

Thiols are made by using alkyl halides and the hydrosulfide anion (SH anion), which acts as a nucleophile in the reaction to create a thiol. The hydrosulfide anion attacks the carbon atom on the alkyl halide, displacing the bromine or chlorine to make the thiol and a bromine or chlorine anion. The problem with this reaction is that the sulfide side product can be formed by continuation of the reaction. The way around this is to use thiourea as the nucleophile with hydrolyzing the intermediate in a basic solution as is seen in figure 95: