11.13:
Structure and Nomenclature of Thiols and Sulfides
Thiols and sulfides are sulfur equivalents of alcohols and ethers, respectively, where the sulfur atom replaces the oxygen atom of alcohols and ethers.
Thus, thiols have the –SH functional group, also known as the sulfhydryl or the mercapto group, bonded to a hydrocarbon group.
Sulfides, or thioethers, have the central sulfur atom flanked by two hydrocarbon groups on either side.
Accordingly, sulfides can be symmetrical, with two identical groups on both sides, or asymmetrical, with two different groups.
Like alcohols and ethers, thiols and sulfides also exhibit a bent geometry, with the C–S–H and C–S–C bond angles smaller than the corresponding C–O–H and C–O–C bond angles of alcohols and ethers.
When comparing the bond lengths, the C–S bond of thiols and sulfides is longer than the C–O bond of corresponding alcohols and ethers. Similarly, the S–H bond of thiols is longer than the O–H bond of alcohols.
Common names of thiols are derived by adding the suffix "mercaptan" to the name of the alkyl group bonded to the –SH group.
The IUPAC names for thiols use the suffix "thiol" to follow the name of the parent hydrocarbon chain without dropping the letter "e" from the parent chain's name.
The parent chain is numbered from the end close to the –SH group, with the locants indicating the position of the sulfhydryl group and substituents as prefixes.
When present as a substituent, the sulfhydryl group is prefixed as "mercapto" before the parent chain's name.
Common names of sulfides are assigned by adding the suffix "sulfide" to follow the names of alkyl groups listed alphabetically.
When deriving the IUPAC names of sulfides, the longest carbon chain is considered as the parent alkane. The smaller alkyl group containing sulfur is named an alkylthio group and prefixed to the parent alkane's name.
11.13:
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.