Thial

In organic chemistry, a thial or thioaldehyde is a functional group which is similar to an aldehyde, RC(O)H, in which a sulfur (S) atom replaces the oxygen (O) atom of the aldehyde (R represents an alkyl or aryl group).^[1] Thioaldehydes are even more reactive than thioketones. Unhindered thioaldehydes are generally too reactive to be isolated — for example, thioformaldehyde, H₂C=S, condenses to the cyclic trimer 1,3,5-trithiane. Thioacrolein, H₂C=CHCH=S, formed by decomposition of allicin from garlic, undergoes a self Diels-Alder reaction giving isomeric vinyldithiins.^[2][3] While thioformaldehyde is highly reactive, it is found in interstellar space along with its mono- and di-deuterated isotopologues.^[4] With sufficient steric bulk, however, stable thioaldehydes can be isolated.^[5]

Chemical structure of a thial

In early work, the existence of thioaldehydes was inferred by trapping processes. For instance the reaction of Fc₂P₂S₄ with benzaldehyde was proposed to form thiobenzaldehyde, which forms a cycloadduct with the dithiophosphine ylides to form a C₂PS₃ ring.^[6]

See also

• Thioketone
• Thioenol
• Organosulfur compounds

Further reading

• Cooper, N.J. (2005). "Thioaldehydes and Thioketones". Comprehensive Organic Functional Group Transformations II. pp. 355–396. doi:10.1016/B0-08-044655-8/00053-2. ISBN 978-0-08-044655-4.
• Murai, Toshiaki (2018). "The Construction and Application of C=S Bonds". Topics in Current Chemistry. 376 (4): 31. doi:10.1007/s41061-018-0209-0. PMID 29987439. S2CID 51605664.