CH3CS

CH3CS, also known as thioacetaldehyde, is an organic compound with the chemical formula CH3CS. It is a sulfur analog of acetaldehyde, where the oxygen atom in the carbonyl group has been replaced by a sulfur atom. Thioacetaldehyde is an unstable and highly reactive species, making it difficult to isolate and study in its pure form. It readily undergoes polymerization and other reactions.

The molecule features a carbon-carbon double bond and a carbon-sulfur double bond. Due to the presence of the C=S double bond, CH3CS is considered a thioketone. The instability of thioacetaldehyde is attributed to the relatively weak C=S double bond compared to the C=O double bond found in aldehydes and ketones. This weakness makes it prone to Diels-Alder reactions, [2+2] cycloadditions, and nucleophilic attack.

Thioacetaldehyde can be generated in situ through various chemical reactions. For instance, it can be formed by the pyrolysis of certain sulfur-containing organic compounds. Its transient nature means that it is often detected and characterized by spectroscopic methods immediately after its generation, without isolation. Research into thioacetaldehyde primarily focuses on its reactivity and its role as an intermediate in complex organic synthesis pathways. Despite its instability, understanding its chemistry is important for fields such as organic chemistry and theoretical chemistry.