Thiol formation [HS(–)]
Thiol formation (HS‾) Definition:
Alkyl halides (or tosylate) will react with the hydrosulfide anion (HS‾) to give thiols.
Thiol formation (HS‾) Explained:
In a concerted process, nucleophilic attack and loss of a leaving group occur simultaneously. The attack of the nucleophile (hydrosulfide anion) is carried out on the opposite side of the leaving group (bromide). Because of this, backside attack results in inversion of configuration on the chiral center.
In the transition state dotted lines show the partial bonds which are breaking and forming.