11.14: Structure and Nomenclature of Thiols and Sulfides
Thiols and sulfides are sulfur analogs of alcohols and ethers, respectively, where the sulfur atom takes the place of the oxygen atom. Thus, thiols are generally represented as RSH, where R is an alkyl substituent and —SH is the functional group. On the other hand, in sulfides, the central sulfur atom is bonded to two hydrocarbon groups on either side. Depending upon the type of group, sulfides can be either symmetrical or asymmetrical. Both thiols and sulfides display a bent geometry, similar to alcohols and ethers. However, the larger size of the sulfur atom deviates the C–S–C and C–S–H bond angles and the C–S and S–H bond lengths from the corresponding bond angle and bond length values of alcohols and ethers.
Generally, common names of thiols consist of the suffix "mercaptan," following the name of the parent alkyl group. In contrast, the IUPAC names of thiols are obtained by adding the suffix "thiol" to the parent alkane name while retaining the letter "e" of the parent alkane. Similarly, the suffix "sulfide" is added to the alkyl groups' names listed in alphabetical order to derive the common names of sulfides. The IUPAC names of sulfides are obtained by first determining the parent chain and prefixing the name of the smaller alkyl group as an alkylthio substituent to the parent alkane name.