Chemistry:Thioketone
In organic chemistry, thioketones (from grc θεῖον (theion) 'sulfur';[1] also known as thiones or thiocarbonyls) are organosulfur compounds related to conventional ketones in which the oxygen has been replaced by a sulfur.[2] Instead of a structure of R
2C=O, thioketones have the structure R
2C=S, which is reflected by the prefix "thio-" in the name of the functional group. Thus the simplest thioketone is thioacetone, the sulfur analog of acetone. Unhindered alkylthioketones typically tend to form polymers or rings.[3][4]
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°.[5] Unhindered dialkylthiones polymerize or oligomerize but thiocamphor is well characterized red solid.[6]
Consistent with the double bond rule, most alkyl thioketones are unstable with respect to dimerization.[7] The energy difference between the p orbitals of sulfur and carbon is greater than that between oxygen and carbon in ketones.[8] The relative difference in energy and diffusity of the atomic orbitals of sulfur compared with carbon results in poor overlap of the atomic orbitals and the energy gap between the HOMO and LUMO is thus reduced for C=S molecular orbitals relative to C=O.[5] The striking blue appearance of thiobenzophenone is attributed to π→ π* transitions upon the absorption of red light.[8] 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[9] and the related reagent Lawesson's reagent. Other methods uses a mixture of hydrogen chloride combined with hydrogen sulfide. Bis(trimethylsilyl)sulfide has also been employed.[3][10]
Thiobenzophenone [(C6H5)2CS] is a stable deep blue compound that dissolves readily in organic solvents. It photooxidizes in air to benzophenone and sulfur. Since its discovery, a variety of related thiones have been prepared.[11]
Thiosulfines
Thiosulfines, also called thiocarbonyl S-sulfides, are compounds with the formula R2CSS. Although superficially appearing to be cumulenes, 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 dithiiranes, 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.[12]
External links and further reading
- Kroto, H.; Landsberg, B. M.; Suffolk, R. J.; Vodden, A. (1974). "The photoelectron and microwave spectra of the unstable species thioacetaldehyde, CH3CHS, and thioacetone, (CH3)2CS". Chemical Physics Letters 29 (2): 265–269. doi:10.1016/0009-2614(74)85029-3. Bibcode: 1974CPL....29..265K.
- Cooper, N.J. (2005). "Thioaldehydes and Thioketones". Comprehensive Organic Functional Group Transformations II. pp. 355–396. doi:10.1016/B0-08-044655-8/00053-2. ISBN 978-0-08-044655-4.
- Murai, Toshiaki (2018). "The Construction and Application of C=S Bonds". Topics in Current Chemistry 376 (4): 31. doi:10.1007/s41061-018-0209-0. PMID 29987439.
See also
- Thial, for a description of thioaldehydes.
- Thioketene
- Sulfene
- Selone (often called selenone)
References
- ↑ θεῖον , Henry George Liddell, Robert Scott, A Greek–English Lexicon
- ↑ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "Thioketones". doi:10.1351/goldbook.T06356
- ↑ 3.0 3.1 Kuhn, N.; Verani, G. (2007). "Chalcogenone C=E compounds". Handbook of Chalcogen Chemistry: New Perspectives in Sulfur, Selenium and Tellurium. Royal Society of Chemistry. doi:10.1039/9781847557575-00107.
- ↑ E. Champaigne (1966). "Thioketones". in Saul Patai. The Carbonyl Group. PATAI'S Chemistry of Functional Groups. 1. John Wiley & Sons Ltd.. p. 916. doi:10.1002/9780470771051.ch17. ISBN 9780470771051.
- ↑ 5.0 5.1 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. doi:10.1021/ja0377551
- ↑ Brunelli, M.; Fitch, A. N.; Mora, A. J. (2002). "Crystal Structures of R-Thiocamphor". Zeitschrift für Kristallographie - Crystalline Materials 217 (2): 83–87. doi:10.1524/zkri.217.2.83.20627. Bibcode: 2002ZK....217...83B.
- ↑ Organosulfur Chemistry I: Topics in Current Chemistry, 1999, Volume 204/1999, 127-181, doi:10.1007/3-540-48956-8_2
- ↑ 8.0 8.1 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. doi:10.1351/pac199668040789
- ↑ Polshettiwar, Vivek; Kaushik, M. P. (2004). "A new, efficient and simple method for the thionation of ketones to thioketones using P4S10/Al2O3". Tetrahedron Letters 45 (33): 6255–6257. doi:10.1016/j.tetlet.2004.06.091.
- ↑ Mcgregor, W. M.; Sherrington, D. C. (1993). "Some recent synthetic routes to thioketones and thioaldehydes". Chemical Society Reviews 22 (3): 199. doi:10.1039/CS9932200199.
- ↑ Okazaki, R.; Tokitoh, N. (2000). "Heavy ketones, the heavier element congeners of a ketone". Accounts of Chemical Research 33 (9): 625–630. doi:10.1021/ar980073b. PMID 10995200.
- ↑ Rolf Huisgen; J. Rapp (1997). "1,3-Dipolar Cycloadditions. 98. The Chemistry of Thiocarbonyl S-Sulfides". Tetrahedron 53 (3): 939–960. doi:10.1016/S0040-4020(96)01068-X.
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