tiioester

Thioesters are a class of organic compounds with the general formula R-C(=O)-SR', where R and R' are organic groups. They are analogous to esters, but with a sulfur atom replacing the oxygen atom of the carboxyl group. The sulfur atom is typically bonded to the carbonyl carbon and the R' group. Thioesters are formed through the reaction of a carboxylic acid or its derivative with a thiol. These reactions can occur under acidic or basic conditions, or with the aid of coupling reagents.

Thioesters play crucial roles in biochemistry. A particularly important example is acetyl-CoA, which is central to cellular metabolism, including the citric acid cycle and fatty acid synthesis. The thioester bond in acetyl-CoA is a high-energy bond, meaning that its hydrolysis releases a significant amount of free energy. This energy can be harnessed to drive other biochemical reactions. Other biologically relevant thioesters include succinyl-CoA and malonyl-CoA.

In organic synthesis, thioesters can serve as intermediates or protecting groups. They can be prepared from carboxylic acids using thiols and activating agents, or by reaction of acyl halides or anhydrides with thiols. Thioesters are generally more reactive than their oxygen ester counterparts due to the weaker C-S bond compared to the C-O bond and the greater polarizability of sulfur. This increased reactivity can be advantageous in certain synthetic transformations.