{{Short description|1=Chemical group (–CH=S)}} thumb|right|150px|Chemical structure of a thial
In organic chemistry, a '''thial''' or '''thioaldehyde''' is a functional group which is similar to an aldehyde, {{chem2|RC(O)H}}, in which a sulfur (S) atom replaces the oxygen (O) atom of the aldehyde (R represents an alkyl or aryl group).<ref name= Whittingham>{{cite book |last1=Whittingham |first1=William G. |title=Comprehensive Organic Functional Group Transformations |chapter=Thioaldehydes and Thioketones |date=1995 |pages=329–380 |doi=10.1016/B0-08-044705-8/00169-2 |isbn=978-0-08-044705-6 }}</ref> Thioaldehydes are even more reactive than thioketones. Unhindered thioaldehydes are generally too reactive to be isolated — for example, thioformaldehyde, {{chem2|H2C\dS}}, condenses to the cyclic trimer 1,3,5-trithiane. Thioacrolein, {{chem2|H2C\dCHCH\dS}}, formed by decomposition of allicin from garlic, undergoes a self Diels-Alder reaction giving isomeric vinyldithiins.<ref>{{cite journal | journal = Chemical Physics Letters | volume = 29 | issue = 2 | year = 1974 | pages = 265–269 | title = The photoelectron and microwave spectra of the unstable species thioacetaldehyde, CH 3CHS, and thioacetone, (CH 3) 2CS |author1=H. W. Kroto |author2=B. M. Landsberg |author3=R. J. Suffolk |author4=A. Vodden | doi = 10.1016/0009-2614(74)85029-3 | bibcode=1974CPL....29..265K}}</ref><ref>{{cite book|author=E. Block|title=Garlic and Other Alliums: The Lore and the Science|url=https://books.google.com/books?id=6AB89RHV9ucC|publisher=Royal Society of Chemistry|year=2010|isbn=978-0-85404-190-9}}</ref> While thioformaldehyde is highly reactive, it is found in interstellar space along with its mono- and di-deuterated isotopologues.<ref>{{Cite web|url=http://www.astro.uni-koeln.de/site/vorhersagen/molecules/ism/H2CS.html|title = CDMS}}</ref> With sufficient steric bulk, however, stable thioaldehydes can be isolated.<ref>{{cite journal |author1=N. Takeda |author2=N. Tokitoh |author3=R. Okazaki | title = Synthesis, Structure, and Reactions of the First Rotational Isomers of Stable Thiobenzaldehydes, 2,4,6-Tris[bis(trimethylsilyl)methyl]thiobenzaldehydes | journal = Chemistry: A European Journal | year = 1997 | volume = 3 | pages = 62–69 | doi = 10.1002/chem.19970030111}}</ref>
Thioacetaldehyde (CH<sub>3</sub>CHS) has been detected in the Taurus Molecular Cloud.<ref name="thioacetaldehyde">{{cite journal |display-authors=1 |last1=Agúndez |first1=M. |last2=Molpeceres |first2=G. |last3=Cabezas |first3=C. |last4=Marcelino |first4=N. |last5=Tercero |first5=B. |last6=Fuentetaja |first6=R. |last7=de Vicente |first7=P. |last8=Cernicharo |first8=J. |title=Detection of thioacetaldehyde (CH 3 CHS) in TMC-1: Sulfur-oxygen differentiation along the hydrogenation sequence |journal=Astronomy & Astrophysics |date=January 2025 |volume=693 |pages=L20 |doi=10.1051/0004-6361/202453459 |arxiv=2501.05125 |url=https://www.aanda.org/articles/aa/full_html/2025/01/aa53459-24/aa53459-24.html}}</ref>
In early work, the existence of thioaldehydes was inferred by trapping processes. For instance the reaction of {{chem2|Fc2P2S4}} with benzaldehyde was proposed to form thiobenzaldehyde, which forms a cycloadduct with the dithiophosphine ylides to form a {{chem2|C2PS3}} ring.<ref>{{cite journal| title = Synthetic Applications of Bis(trimethylsilyl)sulfide: Part II. Synthesis of Aromatic and Heteroaromatic o-Azido-Thioaldehydes|author1=A. Capperucci |author2=A. Degl’Innocenti |author3=P. Scafato |author4=P. Spagnolo | journal = Chemistry Letters| volume = 24| pages = 147| year = 1995| doi = 10.1246/cl.1995.147| issue = 2}}</ref>
==See also== *Thioketone *Thioenol *Organosulfur compounds
==Further reading== * {{cite book |doi=10.1016/B0-08-044655-8/00053-2 |chapter=Thioaldehydes and Thioketones |title=Comprehensive Organic Functional Group Transformations II |date=2005 |last1=Cooper |first1=N.J. |pages=355–396 |isbn=978-0-08-044655-4 }} * {{cite journal |doi=10.1007/s41061-018-0209-0 |title=The Construction and Application of C=S Bonds |date=2018 |last1=Murai |first1=Toshiaki |journal=Topics in Current Chemistry |volume=376 |issue=4 |page=31 |pmid=29987439 |s2cid=51605664 }}
==References== {{Reflist}}
{{Functional group}} {{Authority control}}
Category:Functional groups Category:Thioaldehydes