Thioketone

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General formula of a thioketone

In

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]

Solution and solid samples of thiobenzophenone. The blue color is consistent with a small HOMO–LUMO gap associated with the thiocarbonyl functional group.

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

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

See also

References

  1. ^ θεῖον Archived 2017-05-10 at the Wayback Machine, Henry George Liddell, Robert Scott, A Greek–English Lexicon
  2. doi:10.1351/goldbook.T06356
  3. ^
    doi:10.1039/9781847557575-00107
    .
  4. ISBN 9780470771051
    .
  5. ^
    doi:10.1021/ja0377551
  6. S2CID 97935620
    .
  7. doi:10.1007/3-540-48956-8_2
  8. ^
    doi:10.1351/pac199668040789
  9. doi:10.1016/j.tetlet.2004.06.091
    .
  10. doi:10.1039/CS9932200199
    .
  11. PMID 10995200
    .
  12. doi:10.1016/S0040-4020(96)01068-X
    .
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