Article · Wikipedia archive · Last revised Jun 13, 2026

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. 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. While thioformaldehyde is highly reactive, it is found in interstellar space along with its mono- and di-deuterated isotopologues. With sufficient steric bulk, however, stable thioaldehydes can be isolated.

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Chemical structure of a thial source ↗

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.23 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

Thioacetaldehyde (CH3CHS) has been detected in the Taurus Molecular Cloud.6

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.7

See also

See also

Further reading

Further reading

References

References

  1. Whittingham, William G. (1995). "Thioaldehydes and Thioketones". Comprehensive Organic Functional Group Transformations. pp. 329–380. doi:10.1016/B0-08-044705-8/00169-2. ISBN 978-0-08-044705-6.
  2. H. W. Kroto; B. M. Landsberg; R. J. Suffolk; A. Vodden (1974). "The photoelectron and microwave spectra of the unstable species thioacetaldehyde, CH 3CHS, and thioacetone, (CH 3) 2CS". Chemical Physics Letters. 29 (2): 265–269. Bibcode:1974CPL....29..265K. doi:10.1016/0009-2614(74)85029-3.
  3. E. Block (2010). Garlic and Other Alliums: The Lore and the Science. Royal Society of Chemistry. ISBN 978-0-85404-190-9.
  4. "CDMS".
  5. N. Takeda; N. Tokitoh; R. Okazaki (1997). "Synthesis, Structure, and Reactions of the First Rotational Isomers of Stable Thiobenzaldehydes, 2,4,6-Tris[bis(trimethylsilyl)methyl]thiobenzaldehydes". Chemistry: A European Journal. 3: 62–69. doi:10.1002/chem.19970030111.
  6. Agúndez, M.; et al. (January 2025). "Detection of thioacetaldehyde (CH 3 CHS) in TMC-1: Sulfur-oxygen differentiation along the hydrogenation sequence". Astronomy & Astrophysics. 693: L20. arXiv:2501.05125. doi:10.1051/0004-6361/202453459.
  7. A. Capperucci; A. Degl’Innocenti; P. Scafato; P. Spagnolo (1995). "Synthetic Applications of Bis(trimethylsilyl)sulfide: Part II. Synthesis of Aromatic and Heteroaromatic o-Azido-Thioaldehydes". Chemistry Letters. 24 (2): 147. doi:10.1246/cl.1995.147.