The unexpected desulfurization of 4-aminothiophenols

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Journal titleJournal of Organic Chemistry
Pages23792386; # of pages: 8
SubjectFirst-order kinetics; Hexadecane; Kinetic modeling; Sulfur loss; Amino acids; Aromatic compounds; Phenols; Rate constants; Reaction kinetics; Thermolysis; Desulfurization; 4 aminophenylbenzyl sulfide; 4 aminothiophenol derivative; ampholyte; anthracene; benzylsulfamide; hexadecane; solvent; thiophenol derivative; unclassified drug; article; chemical bond; chemical reaction kinetics; desulfurization; reaction analysis; thermal analysis
AbstractThermolysis of 4-aminophenyl benzyl sulfide at 523 K in the hydrogen donor solvent (HDS), 9,10-dihydroanthracene (AnH2), gave 4-aminothiophenol and toluene as the predominant products of the homolytic S-C bond cleavage. Under these conditions, a portion of the 4-aminothiophenol was desulfurized to aniline with first-order kinetics and with a rate constant estimated by kinetic modeling to be 7.0 × 10-6 s-1. Starting with 4-NH2C6H4SH at 523 K, it was found that sulfur loss was more efficient in the non-HDSs, anthracene and hexadecane, than in AnH2. Under similar (competitive) reaction conditions, YC 6H4SHs with Y = H, 4-CN, and 3-CF3 were completely inert; with Y = 4-CH3O, there was some very minor desulfurization, whereas with Y = 4-N(CH3)2 and 4-N(CH3)(H), the sulfur extrusions were as fast as that for Y = 4-NH2. We tentatively suggest that this apparently novel reaction is a chain process initiated by the bimolecular formation of diatomic sulfur, S2, followed by a reversible addition of ground state, triplet 3S2 to the thiol sulfur atom, 4-NH2C 6H4S↑(SS↑)H, and insertion into the S-H bond, 4-NH2C6H4SSSH. In a cascade of reactions, aniline and S8 are formed with the chains being terminated by reaction of 4-NH2C6H4S↑(SS↑)H with 4-NH2C6H4SH. Such a reaction mechanism is consistent with the first-order kinetics. That this reaction is primarily observed with 4-YC6H4SH having Y = N(CH3) 2, N(CH3)(H), and NH2 is attributed to the fact that these compounds can exist as zwitterions. © 2007 American Chemical Society.
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AffiliationNational Research Council Canada (NRC-CNRC)
Peer reviewedYes
NPARC number21276683
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Record identifier82c1dd4c-26be-4e71-9907-b7e366f1effd
Record created2015-10-13
Record modified2016-05-09
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