Sulfenic acid

A sulfenic acid is an organosulfur compound and oxoacid with the general formula RSOH, where R ≠ H. Simple sulfenic acids, such as methanesulfenic acid, CH3SOH, are highly reactive and cannot be isolated in solution. In the gas phase the lifetime of methanesulfenic acid is about one minute. The gas phase structure of methanesulfenic acid was found by microwave spectroscopy (rotational spectroscopy) to be CH3–S–O–H.[1] Sulfenic acids can be stabilized through steric effects, which prevent the sulfenic acid from condensing with itself to form thiosulfinates, RS(O)SR, such as allicin from garlic. Through the use of X-ray crystallography, the structure of such stabilized sulfenic acids were shown to be R–S–O–H.[2][3]

Sulfenic acids are produced by the enzymatic decomposition of alliin and related compounds following tissue damage to garlic, onions, and other plants of the Allium genus. Mass spectrometry with a DART ion source were used to identify 2-propenesulfenic formed when garlic is cut or crushed and to demonstrate that this sulfenic acid has a lifetime of less than one second.[4]

Sulfenyl group

The prefix sulfenyl in organic nomenclature denotes the RS group (R≠H), for instance an arylsulfenylpyridine Ar-S-Py [5].

References

  1. ^ Penn RE, Block E, Revelle LK (1978). "Methanesulfenic Acid". Journal of the American Chemical Society 100 (11): 3622–3624. doi:10.1021/ja00479a068. 
  2. ^ Goto K, Holler M, Okazaki R (1997). "Synthesis, Structure, and Reactions of a Sulfenic Acid Bearing a Novel Bowl-Type Substituent: The First Synthesis of a Stable Sulfenic Acid by Direct Oxidation of a Thiol". Journal of the American Chemical Society 119 (6): 1460–1461. doi:10.1021/ja962994s. 
  3. ^ Ishii A, Komiya K, Nakayama J (1996). "Synthesis of a Stable Sulfenic Acid by Oxidation of a Sterically Hindered Thiol (Thiophenetriptycene-8-thiol)1 and Its Characterization". Journal of the American Chemical Society 118 (50): 12836–12837. doi:10.1021/ja962995k. 
  4. ^ Block E, Dane AJ, Thomas S, Cody RB (2010). "Applications of Direct Analysis in Real Time–Mass Spectrometry (DART-MS) in Allium Chemistry. 2-Propenesulfenic and 2-Propenesulfinic Acids, Diallyl Trisulfane S-Oxide and Other Reactive Sulfur Compounds from Crushed Garlic and Other Alliums". Journal of Agricultural and Food Chemistry 58 (8): 4617–4625. doi:10.1021/jf1000106. PMID 20225897. 
  5. ^ IUPAC Gold Book http://www.iupac.org/goldbook/S06098.pdf