Thiobenzophenone is an
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 ...
with the formula (C
6H
5)
2CS. It is the prototypical
thioketone
In organic chemistry, thioketones (; also known as thiones or thiocarbonyls) are organosulfur compounds related to conventional ketones in which the oxygen has been replaced by a sulfur. Instead of a structure of , thioketones have the structure ...
. Unlike other thioketones that tend to
dimer
Dimer may refer to:
* Dimer (chemistry), a chemical structure formed from two similar sub-units
** Protein dimer, a protein quaternary structure
** d-dimer
* Dimer model, an item in statistical mechanics, based on ''domino tiling''
* Julius Dimer ...
ize to form rings and polymers, thiobenzophenone is quite stable, although it photoxidizes in air to form benzophenone and sulfur.
Thiobenzophenone is deep blue and dissolves readily in many organic solvents.
Structure
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°.
[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. ] A variety of thiones with structures and stability related to thiobenzophenone have also been prepared.
Synthesis
One of the first reported syntheses of thiobenzophenone involves the reaction of
sodium hydrosulfide
Sodium hydrosulfide is the chemical compound with the formula NaHS. This compound is the product of the half-neutralization of hydrogen sulfide () with sodium hydroxide (NaOH). NaSH and sodium sulfide are used industrially, often for similar purpos ...
and
diphenyldichloromethane
Diphenyldichloromethane is an organic compound with the formula (C6H5)2CCl2. It is a colorless solid that is used as a precursor to other organic compounds.
Synthesis
It is prepared from carbon tetrachloride and anhydrous aluminium chloride as c ...
":
:Ph
2CCl
2 + 2 NaSH → Ph
2C=S + 2 NaCl + H
2S
An updated method involves sulfiding of benzophenone:
:Ph
2C=O + H
2S → Ph
2C=S + H
2O
In the above reaction scheme, a mixture of gaseous hydrogen chloride and
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 ...
are passed into a cooled solution of benzophenone in ethanol. Thiobenzophenone can also be produced by a
Friedel-Crafts reaction of thiobenzoyl chloride and benzene.
Reactivity
Due to the weakness of the C=S bond, thiobenzophenone is more reactive than its C=O benzophenone counterpart. Thiobenzophenone as well as other thioketones are considered to be superdipolarophiles and
dienophiles that rapidly combine with 1,3-dienes in Diels-Alder cycloadditions.
[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 rate of thioketones in cycloadditions is related but not limited to the size of the small HOMO/LUMO energy gap of the π-MOs of the C=S double bond.
Reactions between thiobenzophenone and most dienes yield Diels-Alder adducts whereas reactions with monoolefins yield bicyclic compounds.
[Okuma, K.; Yamamoto, T.; Shirokawa, T.; Kitamura, T.; Fujiwara, Y. "The First Isolation of Benzyne-Thiobenzophenone Adducts". Tetrahedron Letters, 1996, 49, 8883-8886. ]
References
{{reflist
Thioketones
Benzophenones