Sulphur-containing solvents

When working with this solvent, its toxicity (it is a blood and nerve poison) and particularly its high flammability should be borne in mind. Distillation of 

The analytical reagent grade is suitable for most purposes. The commercial substance may be purified by shaking for 3 hours with three portions of potassium permanganate solution (5 g per litre), twice for 6 hours with mercury and finally with a solution of mercury(n) sulphate (2.5 g per litre). It is then dried over anhydrous calcium chloride, and fractionated from a water bath at 55-65 °C. The pure compound boils at 46.5 °C/760 mmHg. 

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Nitrogen-containing solvents 409 Sulphur-containing solvents 411 Phosphorus-containing solvents 412... 

The groups found when classifying by chemical structure have already been mentioned the three main classes used are hydrocarbons, oxygenated and chlorinated solvents. Others, such as nitrogen and sulphur-containing solvents are speciality products and not the main focus of this book. 

Multi-element analyses involving solvent extraction and high performance liquid chromatography (HPLC) have also been described. The extracts, containing metal-chelate complexes with sulphur-containing reagents, such as dithizone and diethyldithiocarbamate, were used directly for determination of the metals by HPLC.14... 

In addition to benzenoid diazo components, diazotised heterocyclic amines in which the amino group is attached to a nitrogen- or sulphur-containing ring figure prominently in the preparation of disperse dyes [87,88], since these can produce marked bathochromic shifts. The most commonly used of these are the 6-substituted 2-aminobenzothiazoles, prepared by the reaction of a suitable arylamine with bromine and potassium thiocyanate (Scheme 4.31). Intermediates of this type, such as the 6-nitro derivative (4.79), are the source of red dyes, as in Cl Disperse Red 145 (4.80). It has been found that dichloroacetic acid is an effective solvent for the diazotisation of 2-amino-6-nitrobenzothiazole [89]. Subsequent coupling reactions can be carried out in the same solvent system. Monoazo disperse dyes have also been synthesised from other isomeric nitro derivatives of 2-aminobenzothiazole [90]. Various dichloronitro derivatives of this amine can be used to generate reddish blue dyes for polyester [91]. 

Table V summarises the data of the sulphur analysis of the hydrocracked liquids and the various bpt fractions for CoMo and NiMo catalysed experiments. The sulphur contents of neither the total hydrocracked liquids nor the individual bpt fractions showed any dependence on repeat contact or catalyst type. The values did show that the sulphur concentrated in the recycle solvent fraction (275-450°C), suggesting that, even under the relatively strong conditions used, certain sulphur-containing compounds will survive to be recycled in the solvent However, the sulphur content of the coal liquid feed was reduced by about 50% and the sulphur content of the likely upgradable product was low.

Lamkin et al. [276] studied in detail the GC analysis of silylated methylthiohydantoins of all protein amino acids. They effected the silylation with BSA-acetonitrile (1 3) at 100°C for 10 min. They separated the products in a simple column packed with 2% of OV-17 on Gas-Chrom Q at 145—230°C, and Fig. 5.20 illustrates the results. The authors used a flame photometric detector, sensitive to sulphur-containing compounds, in order to ensure sensitive and selective detection. Minor incidental peaks that were often noticed during the analysis of the samples obtained by the Edman degradation of proteins with the use of an FID did not appear and the peak of the solvent was not detected. The baseline stability was good and the response was linear over a range of two orders of magnitude of concentration. Asn and Phe were the only unresolved pair Arg, as in previous instances, did not form a volatile derivative. 

In conclusion, we have studied the supported polyoxometalate/H202/solvent system for the oxidation of sulphur containing compounds, and found that significant advantages in terms of product selectivity can be obtained when homogeneous species are immobilized. 

The results of several photolysis reactions of sulphur-containing rings can be rationalized by postulating this process. One example is the photolysis of lipoic acid (182) which yielded 185 (in water) or 186 (in methanol). The proposed mechanism is a homolytic scission of the S—S bond to the diradical 183 and migration of the tertiary hydrogen atom as a radical, to form the thionthiol 184 which reacts with the solvent. A similar mechanism which involves a primary homolytic cleavage of a C—S bond was assumed to occur in the photolysis of mercaptols . 

With the development of the definitions of acids and bases due to Bronsted and Lowry many solvents were found to which these definitions could be applied. It followed, therefore, that solvents were classified as proton containing solvents and proton-free solvents ". The former contain hydrogen in an ionizable form and the cations produced by auto-ionization are considered to be solvated protons. Typical proton-containing solvents are water, liquid ammonia, hydrazine, hydrogen cyanide, sulphuric acid, nitric acid, acetic and formic acids, alcohols and amides. Liquid hydrogen fluoride and the other hydrogen halides may also be included in this group of solvents. 

A new method is described for the quantitative determination of some sulphur-containing antioxidants in PE. The polymer matrix is dissolved in hot n-heptane/ isopropyl alcohol, 97/3 v/v at 160 deg.C under elevated pressure (0.33 MPa) and precipitated by cooling. The solution is injected directly into a normal-phase silica gel column flushed with the same solvent as used for the dissolution of the polymer. This method gives high recovery of the antioxidants, good repeatability of the analysis and a low detection limit of 0.011 mg 4,4 -thiobis(3-methyl-6-tert-butylphenol) (Santonox R) /I g PE 0.074 mg ditetradecyl-beta,beta -thiodipropionate (Chimox 14) / 1... 

C5H10O2, CHjCOOPr. Colourless liquid with a fragrant odour b.p. 88 C. Manufactured by leading propene into hot ethanoic acid containing sulphuric acid, or by heating isopropyl alcohol with ethanoic and sulphuric acids. Used as a solvent for cellulose nitrate and various gums. 

The beat method of drying, if time permits, is to place the crystals in a desiccator containing an appropriate substance (usually anhydrous calcium chloride, silica gel, or concentrated sulphuric acid) to absorb the solvent. More eflicient and more rapid drying is obtained with the aid of a vacuum desiccator (see Section 11,38 and Fig. 77, 38, 1). 

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