Illustrated Glossary of Organic Chemistry

Thioester (thiolester): A functional group characterized by a sulfur atom flanked by one carbonyl group and one carbon of any hybridization.

Generic thioester structure.
R = any carbon group.
   
Phenyl thioacetate
(S-phenyl ethanethioate).

Acetyl-CoA, a coenzyme which supplies two-carbon acetate units for biosynthesis.