The Oxidation of Trialkyl Trithioarsenites, (RS)₃As, by Octasulfur/Triethylamine and Dioxygen

Abstract

Trialkyl trithioarsenites, (RS) 3 As, bearing terminal carboxy ( COOH) or carboxylate ( COO − Na + ) or zwitterionic ( CH(NH 3 + )COO − ) groups were studied for their ability to be oxidized by octasulfur, S 8 , and by dioxygen. The carboxy-bearing trithioarsenites are not oxidized by S 8 to the corresponding As(V) esters, (RS) 3 As=S, probably because they cannot open the octasulfur ring, but they react with S 8 in the presence of triethylamine, which acts as an activator of S 8 . The carboxylatebearing trithioarsenites, however, do react under drastic conditions with S 8 . In both cases colored insoluble solids were obtained which could not be characterized. The carboxy-bearing trithioarsenites are oxidized by air in a hydrocarbon chain-length depended manner, while the carboxylate-bearing trithioarsenites are not, if at all, oxidized by air to arsenic(III) oxide, As 2 O 3 , and disulfide, RSSR. The zwitterionbearing tris(penicillamine), tris(cysteine), and tris(glutathione) trithioarsenites are air oxidized slower than their corresponding parent thiols and this may be of biochemical significance.

The reactions of triethylamine-activated octasulfur with thioarsinites, L2As‒SPh (L = Me, Ph), Bunsen's cacodyl disulfide, Me2As(S)‒S‒AsMe2, and triphenylarsine

“…When octasulfur was activated by catalytic amounts of triethylamine [6], the (ArS) 3 As esters gave disulfides, As 2 O 3 , and colored, insoluble to all common solvents, solids which could not be characterized [3]. The same was observed with certain aliphatic esters (RS) 3 As [7].…”

“…5/5a may have been formed in solution when excess S 8 had been used, but they, too, are not stable, by analogy to 3/3a. From our previous [2,3,5,7] and present work, it seems that the system S 8 /Et 3 N is or can be useful only for the preparation of some sesquisulfides (ArAs) 2 S 3 from ArÀ ÀAs(SPh) 2 [2], and organoarsine sulfides from organoarsines.…”

“…The thioarsenite 1 is oxidized by sulfur slower than 1a and this parallels their air oxidation [24]. From the available qualitative data on the reaction of (ArS) 3 As [3,5], (RS) 3 As [7], LÀ ÀAs(SPh) 2 (L ¼ Me, Ph) [2], 1/1a, 2/2a, and Ph 3 As (this work) toward activated octasulfur, the reactivity follows the order: (ArS) 3 As 4 (RS) 3 As 4 PhÀ ÀAs(SPh) 2 , MeÀ ÀAs(SPh) 2 4 2/2a 4 1/1a 4 Ph 3 As…”

“…Continuing our work on the use of triethylamine-activated octasulfur for the oxidation of As(III) compounds under mild conditions [2,3,5,7], in this article, we report on the reactions of Me 2 AsÀ ÀSPh 1, and Ph 2 AsÀ ÀSPh 1a, with S 8 in the absence and in the presence of catalytic amounts of triethylamine (as an activator of S 8 [6]) in stoichiometries which satisfy the Equations (1)-(3), as well as using excess S 8 or triethylamine, to see whether we can prepare the As(V) compounds 2/2a, 3/3a, and 5/ 5a.…”

Synthesis and Characterization of Organoarsenic(III) Derivatives with 2-Aminocyclopentene 1-Carbodithioc Acid and with Their Nitrogen/Sulfur Alkyl Derivatives

“…In some cases, these bind with the metal through sulfur-sulfur coordination and sulfur-nitrogen coordination. 4 A survey of the literature reveals that only stray references [5][6][7][8] are available in the literature on the synthesis and characterization of organoarsenic (III) derivatives. In view of the above, we were interested in synthesizing and characterizing some organo-arsenic(III) derivatives with the abovementioned ligands.…”