Chemistry:Thioacyl chloride
In organic chemistry, a thioacyl chloride is an organic compound containing the functional group –C(=S)Cl. Their formula is usually written R–C(S)Cl, where R is a side chain. Thioacyl chlorides are analogous to acyl chlorides, but much rarer and less robust. Indeed, one of the simplest, thioacetyl chloride (c.f. acetyl chloride), remained unknown as of 1972.[1]: 350
Most thioacyl halides are "highly coloured, labile oils with pronounced pungent odours".[1]: 358 Simple alkyl derivatives are volatile.[1]: 359
The best studied thioacyl chloride is thiobenzoyl chloride, a purple oil first prepared by chlorination of dithiobenzoic acid with a combination of chlorine and thionyl chloride.[2][1]: 350–351 A more modern preparation employs phosgene as the chlorinating agent,[3] by-producing carbonyl sulfide:
- PhCS2H + COCl2 → PhC(S)Cl + HCl + COS
One example of a thioacyl chloride has been crystallized.[4]
In general, thioacyl chlorides are produced from passing halocarbons through phosphorus pentasulfide or boiling sulfur. Such is the case for the simplest thioacyl chloride, thiophosgene.[1]: 351–352, 354 Thiocarbamyl and -carbonyl chlorides are prepared from the corresponding amines and alcohols by careful thiophosgenation.[1]: 356–358
Reactions
Thioacyl chlorides are electrophilic at the carbon atom. Amines, alcohols, and thiols displace the chloride to form (respectively) thioamides, thionoesters, and dithioesters.[1]: 362–365 Friedel-Crafts reaction thioacylate arenes.[1]: 369–370
Cyanide reacts with thioacyl chlorides to form thioacyl cyanides. These thioacyl cyanides are known to dimerize to dicyanoalkenes, eliminating sulfur.[1]: 365 Likewise thioacyl azide cyclizes to a thiatriazole, and diazo compounds and tetrazoles react to thiadiazoles.[1]: 366–368
Like other unstabilized thiocarbonyls, thioacyl chlorides undergo a variety of dimerization and cycloaddition reactions. "Simple thiocarbonyl halides all show a tendency to dimerize to some degree, especially fluorothioacyl fluorides," the only exception being trifluorothioacetyl fluoride.[1]: 370–371 Carbenes attack the double bond to form episulfides, and the double-bond in general is an extremely active dienophile.[1]: 371–372
Safety
Thioacyl chlorides are toxic.[1]: 359
References
- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 Saul Patai, ed (1972). "Thiocarbonyl halides". Acyl Halides. PATAI'S Chemistry of Functional Groups. pp. 349–380. doi:10.1002/9780470771273.ch11. ISBN 9780470771273.
- ↑ Hermann Staudinger; Siegwart, J. (1920). "Ueber Thiobenzoylchlorid". Helvetica Chimica Acta 3: 824–833. doi:10.1002/hlca.19200030177. https://zenodo.org/record/1426807.
- ↑ "Eine neue Darstellungsmethode für aromatische Thiocarbonsäurechloride". Z. Chem. 15 (9): 348. 1975. doi:10.1002/zfch.19750150904.
- ↑ Ogurtsov, Vladimir A.; Rakitin, Oleg A.; Rees, Charles W.; Smolentsev, Alexey A.; Belyakov, Pavel A.; Golovanov, Denis G.; Lyssenko, Konstantin A. (2005). "Synthesis of Thienothiopyranthiones by a New Molecular Rearrangement". Organic Letters 7 (5): 791–794. doi:10.1021/ol0476669. PMID 15727442.
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