Chapter 15: Alcohols, Diols and Thiols

Thiols

Nomenclature:
Thiols are the sulfur analogues of alcohols.
Functional group suffix = -thiol (review)
Functional group prefix = mercapto-

Physical Properties:

• Hydrogen bonding is much weaker than that in alcohols.
• Lower boiling points than similar alcohols.

• Generally similar to alcohols, but bonds to S are longer and weaker than those to O.
• The thiol functional group consists of an S atom bonded to a C atom and a H atom via s bonds.
• The S-H bonds is less polar than that in alcohols since S is less electronegativity than O.

• Thiols are much more acidic than similar alcohols, e.g. RSH (pK_a = 10) versus ROH (pK_a = 16 to 19)
• Thiols are also much more nucleophilic than similar alcohols, infact RSH is about as nucleophilic as RO^-
• Thiols are readily oxidised but to S-O systems rather than C=S systems.
• Thiols are commonly oxidised to disulfides, R-S-S-R, a biologically important reaction.

© Dr. Ian Hunt, Department of Chemistry