Active sulphur

Metal deactivator To form inactive protective films on metal surfaces which otherwise might catalyse oxidation and corrosion reactions Trialkyl and triaryl phosphites, organic dihydroxyphosphines, some active sulphur compounds, diamines in lubricating greases, mercaptobenzothiazole and phosphites... 

Recently, sulphur has also been found on the surface of Mars it was probably deposited from the atmosphere and originated in volcanic activity. Sulphur was also found in meteorites which probably originated on Mars (Farquhar et al., 2000). The mean surface temperature is 210 K (at night 150 K and during the day 270 K). 

A method of vulcanising thin rubber articles, now of historical interest only. The products are exposed successively to the gases, sulphur dioxide and hydrogen sulphide, which react to form active sulphur which brings about vulcanisation. 

A curing agent which splits off active sulphur during the vulcanisation reaction. One example is di-morpholinodisulphide (Sulfasan R). 

The activated sulphur compound PhCOCH2SPh has been shown to react in a two stage process to produce, firstly, at lower potential, the monofluoro- derivative, and then, at higher potential, the difluoro-compound, both in good yields... 

NcigSgOg, made by boiling with inactive NagSOg, yields a precipitate of active sulphur on acidification but no activity remains in the S03 solution ... 

The mechanism may involve chelation of metal ions essential for enzyme activity by the oxothiazolidine and dithiocarbamate metabolites of carbon disulphide, which are formed by reaction with glutathione and glycine, respectively. However, reactive metabolites may also be formed such as active sulphur (figure 4,26) which might play a role in the various toxic effects. 

Sieh and Dunham have described an analytical procedure for the estimation of the active sulphur trioxide in pyridine-sulphur trioxide (131) complex. The hydrolysis of the latter when added to water, is completed in one hour. However, when the complex is dissolved in 0.1% water in pyridine solution, complete hydrolysis takes place in 5 minutes. This increased rate of hydrolysis allow the estimation of the complex by Karl Fischer titration with good precision. The reaction was extended to the determination of the active sulphur trioxide in the trimethylamine-sulphur trioxide complex182. A solid adduct of S03 and dimethylformamide has been used as a titrant for the conductiometric titration of aliphatic, aromatic and cyclic amines183. 

The aim of this section is to present a short summary of the processes used for the resolution of some simple phosphonic and phosphinic acid derivatives, and to indicate how the enantiomeric purity of such preparations, and of other optically active sulphur-containing organophosphorus esters, may be assessed. In most of the work to be described the phosphonic monoesters and phosphinic acids contining sulphur or selenium were prepared from the corresponding acid chloride this and other preparative routes are indicated in Scheme 11. 

Le Bel s resolution of a quaternary ammonium compound l abcdX. was doubtful, but Pope, S. J. Peachey, and A. W. Harvey resolved a quaternary nitrogen compound by means of camphorsulphonic acid. S. Smiles and Pope and Peachey prepared optically active sulphur compounds. Pope and Neville a selenium compound, and Pope and Peachey tin compounds. A very simple compound, CHCl SOgH), was resolved by Pope and Read. Pope and C. S. Gibson prepared alkyl derivatives of gold, and Pope and Peachey of platinum. 

Finally, on July 18 Marie and Pierre Curie delivered a report to a session of the Paris Academy of Sciences entitled On a new radioactive substance contained in pitchblende . They reported that they had managed to extract from pitchblende a very active sulphur compound of a metal that had previously been unknown. According to its analytical... 

During vulcanisation, the brass surface is exposed to active sulphur-containing molecules present in the rubber compound and a strong bond is formed between the rubber compound and the tyre cord by the action of an interfacial, non-stoichiometric Cu S layer (x 1.8)... 

The active sulphurating agent is itself produced by a multi-step reaction. The first step involves the reaction of zinc oxide, fatty acid and accelerator to produce the precursor (I) in situ in the rubber. The most common of the so-called accelerators are the thiazoles, the... 

Although the zinc perthiomercaptides are not isolable they are commonly believed to be the active sulphurating agent. Two sets of experimental results will however be cited later which are not entirely in accord with this theory. 

The structures of several natural products containing a thiolan ring have been determined. Among these are breynolide (30), which is a degradation product of a bio-active sulphur-containing glycoside, and several related alkaloids, e.g. thiobinupharidine (31), isolated from Nuphar plant material. ... 

No.3, 18th April 1996, p.425-30 THIURAM ACCELERATED SULPHUR VULCANISATION. I. THE FORMATION OF THE ACTIVE SULPHURATING AGENT... 

Duralink HTS 1,6-hexamethylenebissodium thiosulphate (Flexsys America) was used as a post-vulcanisation stabiliser in the sulphur vulcanisation of an NR compound. The effects of this additive on the cure characteristics and on the tensile properties and tear strength of vulcanisates were investigated. The improved reversion resistance, network sulphur rank analysis on overcure and the stoichiometric dependence of activation energy on HTS level supported the conclusion that the active sulphurating species was altered. Improvements in tear strength at equal modulus were consistent with the formation of a bimodal network. 16 refs. 

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