Thial
Encyclopedia
A thial or thioaldehyde is a functional group
Functional group
In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...

 in organic chemistry
Organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...

 which is similar to an aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....

, RC(O)H, in which a sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

 (S) atom replaces the oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 (O) atom of the aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....

 (R represents an alkyl or aryl
Aryl
In the context of organic molecules, aryl refers to any functional group or substituent derived from an aromatic ring, be it phenyl, naphthyl, thienyl, indolyl, etc....

 group). Thioaldehydes are even more reactive than the thioketone
Thioketone
Thioketones are organosulfur compounds related to conventional ketones. Instead of the formula R2C=O, thioketones have the formula R2C=S. Unhindered alkylthioketones are typically unstable; such compounds tend to form polymers or rings.-Preparative methods:Thiones are usually prepared from ketones...

s. Unhindered thioaldehydes are generally unstable — for example, thioformaldehyde, H2C=S, condenses to the cyclic trimer 1,3,5-trithiane
1,3,5-Trithiane
1,3,5-Trithiane is the chemical compound with the formula 3. This heterocycle is the cyclic trimer of the otherwise unstable species thioformaldehyde. It consists of a six-membered ring with alternating methylene and thioether groups...

. With sufficient steric bulk, however, stable thioaldehydes can be isolated.

In early work, the existence of thioaldehydes was inferred by trapping processes. For instance the reaction of Fc2P2S4
1,3,2,4-Dithiadiphosphetane 2,4-disulfides
1,3,2,4-Dithiadiphosphetane 2,4-disulfides are a class of four-membered ring compounds which contain a P2S2 ring, many of these compounds are able to act as sources of the dithiophosphine ylides...

 with benzaldehyde
Benzaldehyde
Benzaldehyde is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. This colorless liquid has a characteristic pleasant almond-like odor...

was proposed to form thiobenzaldehyde, which forms a cycloadduct with the dithiophosphine ylides to form a C2PS3 ring.
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