Trimethylsulfonium
Names
IUPAC name
Trimethylsulfonium
Systematic IUPAC name
Trimethylsulfanium
Other names
  • Trimesium
  • Trimethylsulfur(1+)
Identifiers
3D model (JSmol)
ChemSpider
UNII
  • InChI=1S/C3H9S/c1-4(2)3/h1-3H3/q+1
    Key: NRZWQKGABZFFKE-UHFFFAOYSA-N
  • C[S+](C)C
Properties
(CH3)3S+
Molar mass 77.17 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Trimethylsulfonium (systematically named trimethylsulfanium) is an organic cation with the chemical formula (CH3)3S+ (also written as C3H9S+).

Compounds

Structure of (CH3)3S+ in its tetraphenylborate salt.[1]

Several salts of trimethylsulfonium are known. X-ray crystallography reveals that the ion has trigonal pyramidal molecular geometry at sulfur atom, with C-S-C angles near 102° and C-S bond distance of 177 picometers. Unless the counteranion is colored, all trimethylsulfonium salts are white or colorless.

Salt Formula Molecular weight (g/mol) Properties[2]
Trimethylsulfonium chloride [(CH3)3S]+Cl− 112.5 Colorless crystals, decompose at 100 °C, very soluble in ethanol, very hygroscopic.[3]
Trimethylsulfonium bromide [(CH3)3S]+Br− 157 Colorless crystals. Decomposes at 172 °C, melts in a sealed tube at 201-201 °C, reacts in neutral aqueous solution.[4]
Trimethylsulfonium iodide [(CH3)3S]+I− 204 Colorless crystals, decomposes at 203-207 °C.[4][5] crystal structure monoclinic, with these parameters: a = 5.94 μm, b = 8.00 μm, c = 8.92 μm, β = 126°32′ 2 formulas per unit cell, density = 1.958 g/cm3[6]
Trimethylsulfonium tetrafluoroborate [(CH3)3S]+[BF4]− 163.97 melting point = 205-210 °C[7]
Trimethylsulfonium methylsulfate [(CH3)3S]+CH3OSO−3 188.27 melting point = 92-94 °C[8] Crystal structure orthorhombic with these parameters: a = 12.6157 μm, b = 8.2419 μm, c = 7.540 μm cell volume 784.0 2 formulas per unit cell

Preparation

Sulfonium compounds can be synthesised by treating a suitable alkyl halide with a thioether. For example, the reaction of dimethyl sulfide with iodomethane yields trimethylsulfonium iodide:

(CH3)2S + CH3I → [(CH3)3S]+I−

An extra oxygen atom can bond to the sulfur atom to yield the trimethylsulfoxonium ion [(CH3)3S=O]+, where the sulfur atom is tetravalent and tetracoordinated.

Use

Glyphosate herbicide is often supplied as a trimethylsulfonium salt, referred to as trimesium.[9]

When mixed with aluminium bromide, or aluminium chloride or even hydrogen bromide, trimethylsulfonium bromide forms an ionic liquid, which melts at temperatures below standard conditions.[10]

References

  1. ↑ Knop, Osvald; Cameron, T. Stanley; Bakshi, Pradip K.; Linden, Antony; Roe, Stephen P. (1994). "Crystal chemistry of tetraradial species. Part 5. Interaction Between Cation Lone Pairs and Phenyl Groups in Tetraphenylborates: Crystal Structures of Me3S+,Et3S+, Me3SO+, Ph2I+, and 1-Azoniapropellane Tetraphenylborates". Canadian Journal of Chemistry. 72 (8): 1870–1881. doi:10.1139/v94-238.
  2. ↑ Heilbron's Dictionary of Organic Compounds, volume 4, revised edition published in 1953. Published in Great Britain
  3. ↑ Blättler, H. (1919). "Über Trimethylsulfoniumverbindungen". Monatshefte für Chemie und verwandte Teile anderer Wissenschaften. 40 (8): 417–429. doi:10.1007/BF01559085. S2CID 197766904.
  4. 1 2 Steinkopf, W.; Müller, S. (1923). "Über die Einwirkung von Jodmethyl auf Disulfide". Chem. Ber. 56 (8): 1926–1930. doi:10.1002/cber.19230560834.
  5. ↑ Mussgnug, F. (1941). "Trimethylammoniumjodid und Trimethylsulfoniumjodid". Naturwissenschaften. 29 (17): 256. Bibcode:1941NW.....29..256M. doi:10.1007/BF01479158. S2CID 33842580.
  6. ↑ Zuccaro, D. Ε.; McCullough, J. D. (1 January 1959). "The crystal structure of trimethylsulfonium iodide". Zeitschrift für Kristallographie - Crystalline Materials. 112 (1–6): 401–408. doi:10.1524/zkri.1959.112.jg.401. S2CID 98338161.
  7. ↑ "Trimethylsulfonium tetrafluoroborate". Sigma-Aldrich. Retrieved 23 September 2016.
  8. ↑ "Trimethylsulfonium methyl sulfate". Sigma-Aldrich. Retrieved 23 September 2016.
  9. ↑ "Glyphosate-trimesium". PubChem.
  10. ↑ Ma, M.; Johnson, K.E. (April 1995). "Some physicochemical characteristics of molten salts derived from trimethylsulfonium bromide". Canadian Journal of Chemistry. 73 (4): 593–598. doi:10.1139/v95-076.

See also

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