- The antioxidant activity of polysulfides: It's radical!
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Olefin sulfurization, wherein alkenes and sulfur are heated together at high temperatures, produces branched polysulfides. Due to their anti-wear properties, they are indispensible additives to lubricants, but are also added to other petroleum-derived products as oxidation inhibitors. Polysulfides also figure prominently in the chemistry and biology of garlic and other plants of the Allium species. We previously reported that trisulfides, upon oxidation to their corresponding 1-oxides, are surprisingly effective radical-trapping antioxidants (RTAs) at ambient temperatures. Herein, we show that the homolytic substitution mechanism responsible also operates for tetrasulfides, but not trisulfides, disulfides or sulfides. Moreover, we show that this reactivity persists at elevated temperature (160 °C), enabling tetrasulfides to not only eclipse their 1-oxides as RTAs, but also hindered phenols and alkylated diphenylamines-the most common industrial antioxidant additives. The reactivity is unique to higher polysulfides (n ≥ 4), since homolytic substitution upon them at S2 yields stabilized perthiyl radicals. The persistence of perthiyl radicals also underlies the greater reactivity of polysulfides at elevated temperatures relative to their 1-oxides, since homolytic S-S bond cleavage is reversible in the former, but not in the latter. These results suggest that olefin sulfurization processes optimized for tetrasulfide production will afford materials that impart significantly better oxidation stability to hydrocarbon-based products to which polysulfides are added. Moreover, it suggests that RTA activity may contribute to the biological activity of plant-derived polysulfides.
- Chauvin, Jean-Philippe R.,Griesser, Markus,Pratt, Derek A.
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p. 4999 - 5010
(2019/05/29)
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- A rapid, efficient and green procedure for transformation of alkyl halides/ tosylates to organochalcogens in water
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A one-pot and efficient synthesis of dialkyl dichalcogenides (S, Se) in aqueous media under catalyst-free conditions using benzylic, allylic and primary halides with elemental sulfur and selenium has been developed. Also, this procedure was extended to preparation of trisulfides and triselenides from secondary and tertiary halides in same condition. In all cases, products can be obtained in good to excellent yield in short reactions time.
- Soleiman-Beigi, Mohammad,Yavari, Issa,Sadeghizadeh, Fatemeh
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- Simple and green method for synthesis of symmetrical dialkyl disulfides and trisulfides from alkyl halides in water; PMOxT as a sulfur donor
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An environmentally new, mild and efficient method has been developed for the synthesis of dialkyl disulfides and dialkyl trisulfides in aqueous conditions by a reaction between alkyl halides (and tosylate) and potassium-5-methyl-1,3,4-oxadiazole-2-thiolate (PMOxT) as a sulfur transfer reagent. The advantages of this method are that it occurs under mild reaction conditions, it is base free, it uses water as the solvent and it occurs in high yields. A variety of dialkyl disulfides and dialkyl trisulfides can be obtained in good to excellent yields up to 98%.
- Soleiman-Beigi, Mohammad,Mohammadi, Fariba
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p. 134 - 141
(2017/03/07)
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- Unexpected reactivity of the Burgess reagent with thiols: Synthesis of symmetrical disulfides
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(Equation Presented) Reaction of the Burgess reagent with a series of aliphatic and aromatic thiols led to the corresponding symmetrical disulfides in high yields. No olefins were detected in the reactions of aliphatic thiols.
- Banfield, Scott C.,Omori, Alvaro Takeo,Leisch, Hannes,Hudlicky, Tomas
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p. 4989 - 4992
(2008/02/05)
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- Oxidation of thiols to bisulfides by elemental sulfur without contamination by higher polysulfides
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Dialkyl disulfides were prepared in near quantitative yield by oxidation of alkanethiols with elemental sulfur using NaOH and ethoxylated alcohols as catalysts. Tergitol 15-S-7 was one of several ethoxylated alcohols which was used. Contamination by trisulfides was essentially eliminated in the disulfide products. The ratios of disulfide to trisulfide ranged from 100/0 to 99.6/0.4 for reactions with primary and secondary alkanethiols (100% excess) such as 1-propanethiol, 1-octanethiol, 2-propanethiol, and 2-butanethiol. The process did not work for tertiary alkanethiols such as 2-methyl-2-propanethiol where the trisulfide was greatly favored.
- Shaw, James E.,McAfee, Marilyn G.
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p. 125 - 131
(2007/10/03)
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- Use of a sacriflcial-sulfur electrode in electroorganic chemistry. V. Formation of the sequence CSSSC from S and thiols or thiolates
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At a working potential of about +2.0 V (vs SCE) the carbon-sulfur electrode is a source of the electrogenerated cation S2+. In organic media, this electrophile reacts with thiols (or thiolates) to give a mixture of polysulfides of which the trisulfide is the main product. The reaction between electrogenerated Sy2- and alkyl halides is less selective. Elsevier,.
- Do, Quang Tho,Elothmani, Driss,Simonet, Jacques,Guillanton, Georges Le
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p. 273 - 281
(2007/10/03)
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- The Chemistry of Alkylsulfenyl Alkylsulfinyl Thioanhydrides. The Mechanism of Decomposition
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The decomposition mechanism of alkylsulfenyl alkylsulfinyl thioanhydrides has been investigated.Although the product mixture is complex in most cases, a detailed decomposition study as well as a careful analysis of the products allows for a proposal for a general mechanism which is interesting and not simple.We find, however, that the decomposition process is consistent with that of related systems.
- Derbesy, Gerard,Harpp, David N.
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p. 4468 - 4474
(2007/10/02)
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- Process for treating organic polysulfide compounds
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A process for reducing the metal corrosiveness of an organic polysulfide comprises contacting the polysulfide with a metal such as a transition metal at an elevated temperature. A process for reducing the concentration of a polysulfide, having four or more sulfur atoms in the polysulfide molecule, in a polysulfide mixture is also provided which comprises contacting the polysulfide mixture with a metal such as a transition metal. Further provided is a process for reducing the concentration of an organic trisulfide in a mixture of an organic disulfide and trisulfide wherein the process comprises contacting the mixture with a metal such as a transitional metal.
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- A simple method to prepare unsymmetrical di- tri- and tetrasulfides
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Unsymmetrical di- tri- and tetrasulfides can be prepared in a one-pot reaction using SO2Cl2 SCl2 and S2Cl2 respectively to permit coupling of the appropriate thiols.
- Derbesy, Gerard,Harpp, David N.
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p. 5381 - 5384
(2007/10/02)
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- Peroxidation of S-(2-Methyl-2-propyl) 2-Methyl-2-propanesulfinothioate
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Oxidation of 1 equiv of S-(2-methyl-2-propyl) 2-methyl-2-propanesulfinothioate (1) with 2 equiv of m-chloroperoxybenzoic acid (MCPBA) gives S-(2-methyl-2-propyl) 2-methyl-2-propanesulfonothioate (4, 13percent), 2-methyl-2-propanesulfenic 2-methyl-2-propanesolfonic thioanhydride (5, 32percent), 2-methyl-2-propyl-3-chlorobenzoate (11, 4percent), 2-methyl-2-propyl 2-methyl-2-propanesulfinate (12, 22percent), and small amounts of bis(2-methyl-2-propyl) trisulfide (7) and bis(2-methyl-2-propyl) tetrasulfide (10).Possible mechanisms for product formation are discussed.
- Freeman, Fillmore,Lee, Choonsun
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p. 1263 - 1266
(2007/10/02)
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- VOLATILE POLYSULPHIDES OF ASAFOETIDA
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By means of steam distillation, adsorption chromatography and GC/MS analysis, seven sulphur components (di-, tri- and tetrasulphides) have been characterized in addition to those previously reported from Ferula asafoetida of Afghan origin.The identity of some of the components has been confirmed by synthesis and comparison of GC retentions.The quantitative composition of the constituents in the volatile oil has also been determined.Key Word Index - Ferula asafoetida; Umbelliferae; volatiles; oleoresin; 2-butyl methyl disulphide; 2-butyl methyltrisulphide; and di-2-butyl tetrasulphide.
- Rajanikanth, B.,Ravindranath, B.,Shankaranarayana, M. L.
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p. 899 - 900
(2007/10/02)
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- Electro-organic Reactions. Part 24. Preparative and Mechanistic Aspects of the Anodic Oxidation of Dithioacetals and 1,3-Dithianes
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Anodic oxidation of the title compounds is a convenient and efficient method for deprotection, i.e. for the regeneration of carbonyl compounds. A detailed investigation of sulphur-containing products confirmed that the initial, 2 F mol-1, products are disulphides which, in aqueous acetonitrile, are oxidised further to alkyl alkane thiosulphinates and the corresponding thiosulphonates.In some cases alkyl polysulphides and N-alkylacetamides are important products.Unsymmetrical dithioacetals are oxidised anodically to the three possible disulphides, i.e. cross-coupling occurs.Unsymmetrical disulphides are similarly oxidised to a complex mixture of symmetrical and unsymmetrical thiosulphinates and thiosulphonates. These results, combined with those of cyclic voltammetric and coulometric experiments, suggest a mechanism in which the key step in carbon-sulphur bond cleavage in the initially formed radical cation.The direction of the cleavage is determined by understandable substituent effects.
- Porter, Quentin N.,Utley, James H. P.,Machion, Pedro D.,Pardini, Vera L.,Schumacher, Paolo R.,Viertler, Hans
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p. 973 - 979
(2007/10/02)
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- REACTION OF SULFUR DIOXIDE WITH THIOLS CATALYZED BY BORON TRIFLUORIDE ETHERATE. EVIDENCE FOR A POSSIBLE INTERVENTION OF DITHIOSULFITE AS A REACTION INTERMEDIATE.
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The reaction of sulfur dioxide (SO//2) with 1-propanethiol (NPT), 2-propanethiol (IPT), or 2-methyl-2-propanethiol (TBT) catalyzed by boron trifluoride ethrate (BF//3OEt//2) was investigated. The ratios of dialkyl trisulfide to dialkyl disulfide obtained (RSSSR/RSSR) at an early stage of the reaction were larger than 1 for the reaction of TBT and less than 1 for the reaction of NPT or IPT. The reaction of dithiosulfites with BF//3OEt//2 in the presence or absence of thiol was investigated. From a consideration of the similarity of the composition of the sulfides formed in the reaction of dithiosulfites with BF//3OEt//2 to those in the reaction of SO//2 witn thiol in the presence of BF//3OEt//2, the possibility of the intervention of dithiosulfite as a reaction intermediate in the reaction of SO//2 with thiol is discussed.
- Akiyama
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p. 2657 - 2660
(2007/10/02)
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- Desulfurization of Organic Trisulfides by Tris(dialkylamino)phosphines. Mechanistic Aspects
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Tris(dialkylamino)phosphines effect a rapid desulfurization of trisulfides to disulfides under mild conditions.The reaction mechanism involves a bimolecular process, proceeding by the rate-determining formation of a phosphonium salt intermediate.The central sulfur atom of a diaryl trisulfide is removed in the process, while a dialkyl trisulfide loses a terminal sulfur atom to the aminophosphine.
- Harpp, David N.,Ash, David K.,Smith, Roger A.
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p. 5155 - 5160
(2007/10/02)
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- A NEW SYNTHESIS OF ORGANIC TRISULFIDES
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Thiols react with diimidazolylsulfide under mild conditions to give simmetrical trisulfides in good yield and high purity.
- Banerji, Asoke,Kalena, Govind P.
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p. 3003 - 3004
(2007/10/02)
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