Aliphatic disulphides

Trisubstit jted benzenes Aliphatic disulphides Thiophenes Primary thinaThides... 

In Raman spectra, the S-S stretching vibration gives rise to a strong polarised band whereas, in infrared spectra, because of the symmetry of the S-S group, aliphatic disulphides have two weak bands. These bands occur at... 

Aromatic disulphides and diselenides adopt a conformation in which the torsion angle between the C—S—S— and —S—S—C— planes lies between 70 and 90°. Related studies of aliphatic disulphides have also been undertaken. Comparisons of S, Se, and O analogues represented by ArXMe, (At = Ph or mem-substituted phenyl) and aryl diarylmethyl sulphides have been made, in terms of their conformational behaviour. Studies of diaryl ditellurides ArTeTeAr and phenyl tellurobenzoates PhCOTeR provide dipole-moment data consistent with a non-planar C conformation and planar Z conformation,... 

Aliphatic hydrocarbons (bp 50-200°C) Allyl propyl disulphide Amines (general)... 

The nature of the amino acid residues is of prime importance in the development and maintenance of protein structure. Polypeptide chains composed of simple aliphatic amino acids tend to form helices more readily than do those involving many different amino acids. Sections of a polypeptide chain which are mainly non-polar and hydrophobic tend to be buried in the interior of the molecule away from the interface with water, whereas the polar amino acid residues usually lie on the exterior of a globular protein. The folded polypeptide chain is further stabilized by the presence of disulphide bonds, which are produced by the oxidation of two cysteine residues. Such covalent bonds are extremely important in maintaining protein structure, both internally in the globular proteins and externally in the bonding between adjacent chains in the fibrous proteins. 

Aromatic and aliphatic thiols are oxidized by quaternary ammonium dichromate salts to disulphides (8, 13]. Yields are very good, even with the oxidative dimerization of diethyl phosphorothiolothionate to the corresponding disulphide (79%). 

Aliphatic and aromatic sulphonic acids have been reduced to symmetrical disulphides in almost quantitative yields using potassium iodide and ethyl polyphosphate... 

Carbon disulphide reacts additively with primary and secondary aliphatic amines to form alkylammonium salts of alkyldithiocarbamic acids. The products obtained with dimethylamine, diethylamine and piperidine, also certain derivatives of these products, are manufactured on a large scale for use as accelerators in the vulcanisation of rubber. With aromatic amines the disulphide reacts with elimination of hydrogen sulphide and formation of substituted thio-ureas, e.g. thiocarbanilide. 

DIB in combination with sodium azide and diphenyl disulphide or diphenyl diselenide can replace the methinic hydrogen of aliphatic, aromatic and heteroaromatic aldehydes by the phenylthio or phenylseleno group. The corresponding esters were obtained in moderate (for unsaturated aldehydes) to very good yields [109] ... 

Thiolate ions have been reported to undergo reactions with aliphatic a-halonitro compounds5114,115 to yield the substitution products a-nitrosulphides or disulphides by oxidative dimerization. The substitution reaction is favoured by weakly nucleophilic thiolate ions and proceeds by an S l mechanism. On the other hand, strongly nucleophilic thiolate ions favour the redox reaction by an ionic abstraction (X-philic) mechanism. 

Aromatic, benzylic, and aliphatic thiols 135 are oxidized to the corresponding disulphides 136 by sodium tellurite under phase transfer conditions200 (Scheme 73). 

Liquids agreeing with (3) are called normal liquids they include benzene and other hydrocarbons (aliphatic and aromatic), ether, carbon tetrachloride, carbon disulphide, ethyl iodide, nickel carbonyl, sulphuryl chloride, sulphur chloride, phosphorus trichloride, phosphorus oxychloride, silicon tetrachloride, and nitrogen dioxide. 

A9.6.4.7 The Nordic Council of Ministers issued a report (Pederson et al, 1995) entitled Environmental Hazard Classification, that includes information on data collection and interpretation, as well as a section (5.2.8) entitled QSAR estimates of water solubility and acute aquatic toxicity . This section also discusses the estimation of physicochemical properties, including log Kow For the sake of classification purposes, estimation methods are recommended for prediction of minimum acute aquatic toxicity, for ...neutral, organic, non-reactive and non-ionizable compounds such as alcohols, ketones, ethers, alkyl, and aryl halides, and can also be used for aromatic hydrocarbons, halogenated aromatic and aliphatic hydrocarbons as well as sulphides and disulphides, as cited in an earlier OECD Guidance Document (OECD, 1995). The Nordic document also includes diskettes for a computerized application of some of these methods. 

Acid Chlorides. Phenyl dichloroarsine, when treated with the aliphatic acid chlorides, e.g., acetyl chloride, in carbon disulphide solution and in presence of aluminium chloride, forms acetophenone and arsenic trichloride ... 

Acyl Chlorides. When diphenyl chloroarsine is treated with one of the aliphatic acyl chlorides, like acetyl chloride, dissolved in carbon disulphide and in presence of aluminium chloride, acetophenone and arsenic trichloride are formed ... 

With carbon disulphide. Another reaction which distinguishes the aromatic amines from the aliphatic amines is the one with carbon disulphide. When methyl amine is treated with carbon disulphide a product is obtained according to the following reaction ... 

No successful attempts to observe the spectrum of the thiophenoxy radical or its unhindered substituted analogues have been reported in solution studies. Smentowski (1963) found that the p-chlorobenzene-thiolate anion reacts with nitrosobenzene to give the spectrum of the latter s radical-anion (flow system) and a high yield of the disulphide thep-chlorothiophenoxy radical is apparently formed as an intermediate but dimerizes too rapidly for spectroscopic detection. The spectra of both aromatic and aliphatic thiol radicals have, however, been observed when the species, generated by ultraviolet irradiation of the corresponding disulphides, are trapped in the solid state (Smissman and Sorensen, 1965 Windle et al., 1964). 

Two different methods for introducing disulphide bonds or cross-links have been reported. In the first, an aliphatic isocyanate with a pyridyl-protected... 

This section covers the preparation of sulphonic acids by the oxidation of three different types of sulphur-containing functionality. Thiols, disulphides and related functional group oxidations are covered in the first part. The oxidation of both thiols and disulphides to sulphonic acids is one of the classical methods for the preparation of aliphatic and aromatic sulphonic acids. 

Secondary phosphine sulphides can be obtained in a variety of reactions including the action of caustic soda on aliphatic diphosphine disulphides, or hydrogen sulphide on phosphinous amides. Secondary phosphine sulphides readily add more sulphur to give phosphino dithioic acids (6.79) -an excess produces diphosphine derivatives (below). 

Simple phosphonothious (9.454a) or primary phosphinodithioic (9.454b) acids are unknown. Esters of (9.454a) can, however, be made by reacting primary phosphines with sulphenyl chlorides (9.455), disulphides (9.456) or from phosphonous amides (9.457). Phosphonodithious (thiophosphonous) esters react with aliphatic thiols or sulphur to give phosphonotrithioic (thiophosphonic) esters (9.458). 

Aliphatic and aromatic thiols are easily oxidized to disulphides in aqueous or alcoholic solutions under both acid and alkaline conditions. Higher molecular weight thiols are better oxidized as copper salts . Particularly in the presence of aliphatic amines the oxidation is easily carried out also in hydrocarbon solvents . 

In hydrocarbons, and more generally in aprotic solvents, lower molecular weight aliphatic peracids are quite effective in oxidizing thiols to disulphides. 

Aliphatic and aromatic thiols are oxidized by a variety of reagents to disulphides and to higher oxidation products depending on the specific reaction conditions (Scheme 1). 

When thiols and olefins are co-oxidized in the presence of an aliphatic amine, the end-products are 2-mercaptoethanols, disulphides and water (equation 101). 

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