Esterthiol

Esterthiol is not a widely used term with a single, well-defined meaning in chemistry. In literature it is sometimes applied ambiguously to two related concepts: thioesters, which have the structure R-CO-S-R', and, less commonly, compounds that contain both an ester functional group and a free thiol (-SH) on the same molecule. Because of this ambiguity, precise usage normally specifies thioester or mercaptoester to avoid confusion.

Thioesters are esters in which the alkoxy oxygen of an ordinary ester is replaced by sulfur, giving a carbonyl carbon bonded to sulfur (R-CO-S-R'). They are commonly prepared by coupling carboxylic acids with thiols or by transesterification of thioester derivatives. In biology, acyl-CoA thioesters such as acetyl-CoA and various fatty acyl-CoAs act as activated acyl donors in metabolism. Thioesters are generally more reactive toward hydrolysis and acyl transfer than corresponding oxygen esters because sulfur is a softer, better leaving group than alkoxide. This increased reactivity makes thioesters valuable intermediates in organic synthesis and in enzymatic processes, including peptide and lipid biosynthesis.

Some compounds contain both an ester group and a free thiol group, sometimes called mercaptoesters or thiol esters in a broad sense. The thiol moiety is prone to oxidation to disulfides and to nucleophilic reactions, while the ester can undergo hydrolysis. Such multifunctional molecules are used as building blocks in materials chemistry, as ligands in coordination chemistry, or as intermediates in synthetic sequences that exploit the dual functionality for intramolecular or intermolecular transformations.

Handling and characterization of esterthiol-related species typically involve standard organic methods, with attention to thiol reactivity and potential oxidation. The terminology remains informal in many contexts, so precise description usually specifies thioester or mercaptoester.