![Thioketone Structural Formulae V](https://upload.wikimedia.org/wikipedia/commons/6/65/Thioketone_Structural_Formulae_V.1.png)
In
organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J.; ...
, thioketones (; also known as thiones or thiocarbonyls) are
organosulfur compound
Organosulfur compounds are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g., saccharin. Nature abounds with organosulfur compounds—sulfu ...
s related to conventional
ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...
s in which the oxygen has been replaced by a sulfur. Instead of a structure of , thioketones have the structure , which is reflected by the prefix "
thio-
The prefix thio-, when applied to a chemical, such as an ion, means that an oxygen atom in the compound has been replaced by a sulfur atom. This term is often used in organic chemistry. For example, from the word ''ether,'' referring to an oxyg ...
" in the name of the functional group. Unhindered alkylthioketones typically tend to form
polymers
A polymer (; Greek '' poly-'', "many" + ''-mer'', "part")
is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic an ...
or
rings
Ring may refer to:
* Ring (jewellery), a round band, usually made of metal, worn as ornamental jewelry
* To make a sound with a bell, and the sound made by a bell
:(hence) to initiate a telephone connection
Arts, entertainment and media Film and ...
.
Structure and bonding
The C=S bond length of thiobenzophenone is 1.63 Å, which is comparable to 1.64 Å, the C=S bond length of thioformaldehyde, measured in the gas phase. Due to steric interactions, the phenyl groups are not coplanar and the dihedral angle SC-CC is 36°.
Unhindered dialkylthiones polymerize or oligomerize but thio
camphor
Camphor () is a waxy, colorless solid with a strong aroma. It is classified as a terpenoid and a cyclic ketone. It is found in the wood of the camphor laurel ('' Cinnamomum camphora''), a large evergreen tree found in East Asia; and in the k ...
is well characterized red solid.
Consistent with the
double bond rule
In chemistry, the double bond rule states that elements with a principal quantum number greater than 2 for their valence electrons (period 3 elements and higher) tend not to form multiple bonds (e.g. double bonds and triple bonds). The double bon ...
, most alkyl thioketones are unstable with respect to dimerization.
[Organosulfur Chemistry I: Topics in Current Chemistry, 1999, Volume 204/1999, 127-181, ] The energy difference between the p orbitals of sulfur and carbon is greater than that between oxygen and carbon in ketones.
[Fisera, L.; Huisgen, R.; Kalwinsch, I.; Langhals,E.; Li, X.; Mloston, G.; Polborn, K.; Rapp, J.; Sicking, W.; Sustmann, R. "New Thione Chemistry". Pure Appl. Chem., 1996, 68, 789-798. ] The relative difference in energy and diffusity of the atomic orbitals of sulfur compared to carbon results in poor overlap of the orbitals and the energy gap between the HOMO and LUMO is thus reduced for C=S relative to C=O.
[Sustmann, R.; Sicking, W.; Huisgen, R. "A Computational Study of the Cycloaddition of Thiobenzophenone S-Methylide to Thiobenzophenone". J. Am. Chem. Soc. 2003, 125, 14425-14434. ] The striking blue appearance of thiobenzophenone is attributed to
π→ π* transitions upon the absorption of red light.
Thiocamphor is red.
Preparative methods
Thiones are usually prepared from ketones using reagents that exchange S and O atoms. A common reagent is
phosphorus pentasulfide
Phosphorus pentasulfide is the inorganic compound with the formula (monomer) or (dimer). This yellow solid is the one of two phosphorus sulfides of commercial value. Samples often appear greenish-gray due to impurities. It is soluble in carbon d ...
and the related reagent
Lawesson's reagent
Lawesson's reagent (LR) is a chemical compound used in organic synthesis as a thiation agent. Lawesson's reagent was first made popular by Sven-Olov Lawesson, who did not, however, invent it. Lawesson's reagent was first made in 1956 during a sys ...
. Other methods uses a mixture of
hydrogen chloride
The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride ga ...
combined with
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
.
Bis(trimethylsilyl)sulfide
Bis(trimethylsilyl) sulfide is the chemical compound with the formula ((CH3)3Si)2S. Often abbreviated ( tms)2S, this colourless, vile-smelling liquid is a useful aprotic source of "S2−" in chemical synthesis.
Synthesis
The reagent is prepared ...
has also been employed.
[
]
Thiobenzophenone
Thiobenzophenone is an organosulfur compound with the formula (C6H5)2CS. It is the prototypical thioketone. Unlike other thioketones that tend to dimerize to form rings and polymers, thiobenzophenone is quite stable, although it photoxidizes in ...
6H5)2CS">C6H5)2CSis a stable deep blue
Blue is one of the three primary colours in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model. It lies between violet and cyan on the spectrum of visible light. The eye perceives blue when obs ...
compound that dissolves readily in organic solvents. It photooxidizes in air to benzophenone
Benzophenone is the organic compound with the formula (C6H5)2CO, generally abbreviated Ph2CO. It is a white solid that is soluble in organic solvents. Benzophenone is a widely used building block in organic chemistry, being the parent diarylket ...
and sulfur. Since its discovery, a variety of related thiones have been prepared.
Thiosulfines
Thiosulfines, also called thiocarbonyl ''S''-sulfides, are compounds with the formula R2CSS. Although superficially appearing to be cumulene
In organic chemistry, a cumulene is a compound having three or more ''cumulative'' (consecutive) double bonds. They are analogous to allenes, only having a more extensive chain. The simplest molecule in this class is butatriene (), which is also ...
s, with the linkage R2C=S=S, they are more usefully classified as 1,3-dipoles and indeed participate in 1,3-dipolar cycloadditions. Thiosulfines are proposed to exist in equilibrium with dithiirane
In organic chemistry, episulfides are a class of organic compounds that contain a saturated, heterocyclic ring consisting of two carbon atoms and one sulfur atom. It is the sulfur analogue of an epoxide or aziridine. They are also known as thiira ...
s, three-membered CS2 rings. Thiosulfines are often invoked as intermediates in mechanistic discussions of the chemistry of thiones. For example, thiobenzophenone decomposes upon oxidation to the 1,2,4- trithiolane (Ph2C)2S3, which arises via the cycloaddition of Ph2CSS to its parent Ph2CS.
See also
*Thial
In organic chemistry, a thial or thioaldehyde is a functional group which is similar to an aldehyde, , in which a sulfur (S) atom replaces the oxygen (O) atom of the aldehyde (R represents an alkyl or aryl group). Thioaldehydes are even more rea ...
, for a description of thioaldehydes.
*Thioketene
In organic chemistry, thioketenes are organosulfur compounds analogous to ketenes with the general formula , where R is alkyl or aryl. Thioketene (ethenthione) is also the name of the compound , which is the simplest thioketene. Thioketenes are ...
*Thioacetone
Thioacetone is an organosulfur compound belonging to the -thione group called thioketones, with a chemical formula (CH3)2CS. It is an unstable orange or brown substance that can be isolated only at low temperatures. Above , thioacetone readily co ...
References
External links and further reading
Definition of Selones in the IUPAC Gold Book
*
{{Functional group
Functional groups