Organo-sulfur

As seen in Figure 1, the organo sulfur compounds are methylated at the boiling point (90°C) of dimethyl carbonate, whereas methylation (or alkylation with other alkyl groups) of other functional groups requites higher temperatures. This has resulted in the selective methylation of sulfhydryl groups of compounds that contain other substituents that can be alkylated. The other substituents can then be alkylated at elevated temperatures (63). 

Slimicide and biocide toxic pollutants containing pentachlorophenol are used at mills in the pulp, paper, and paperboard industry. Initially, pentachlorophenol was used as a replacement for heavy metal salts, particularly mercuric types. Trichlorophenols are also used because of their availability as a byproduct from the manufacture of certain herbicides. Formulations containing organo-bromides and organo-sulfur compounds are also being used. Substitution of alternative slimicide and biocide formulations can lead to the virtual elimination of pentachlorophenol and trichlorophenol from these sources. 

This section surveys the most important reactions of chiral organo-sulfur compounds. Some of these were touched on in the previous sections. For the sake of convenience, a variety of reactions occurring at the chiral sulfur center are divided into three main types of reactions racemization, nucleophilic substitution reactions, and electrophilic reactions. 

Hydrocarbon feedstocks for fluid catalytic cracking units (FCCU s) contain organo-sulfur compounds. The sulfur content of these feedstocks is about 0.3% to 3.0%, expressed as elemental sulfur. 

Mushrush, George W. 1992. Fuel instability 2 Organo-sulfur hydroperoxide reactions. Fuel Science and Technology International 10(10) 1563-1600. 

Skeletal-Rearrangement Processes in the Mass Spectra of Organo-Sulfur Compounds J. H. Bowie, B. K. Simons and S. O. Lawesson, Rev. PureAppl. Chem., 1969,19,61-80. 

The stabilization of these heteroaldehydes and -ketones by coordination to transition metals is the subject of this review. Many problems connected with the high reactivity of these heterocarbonyl compounds can be circumvented by using their transition metal complexes. The chemistry of organo-sulfur and organoselenium transition metal complexes in more general terms30,31 and some aspects of thio- and selenoaldehydes and -ketones as... 

Soft metal ions such as Hg11 and Ag1 have long been known to react readily with organo sulfur compounds, and a review of the metal ion-promoted reactions which can occur is available.17... 

Hydroxypropyl methanethiosulfonate. Organo-sulfur group. Good bacterial slime controller for cooling systems with pH below 7.5. Limited value as algaecide or fungicide and at alkaline pH. Typical product is 11 to 12% active, with dose rate of 20 to 100 ppm based on volume. 

At present the exact details of the mechanisms leading to each of the products are far from well understood (7.81. However, it seems likely that oxidation of the common naturally-occurring organo-sulfur compounds (dimethyl sulfide, methyl mercaptan and dimethyl disulfide) proceeds, at least in part, through formation of the methyl thiyl radical, CHjS (4.9-111. That is the main reason for carrying out direct studies on CH3S radical reactions where the individual reactions are isolated. 

Hie determinations of the Laboratoire de Physico-Chimie de r Atmosphere (LPCA) in France (101 are based on measurements of horizontal concentrations s of organo-sulfur compounds close to a local intensive source (algae such as one finds in the Breton coastal area. These results should be... 

Making some assumptions on the chemical filiation between some organo-sulfur compounds, it was possible to establish the mathematical variation law for the concentration ratio of the various detected species and consequently to deduce the depletion rate constant of these compounds. From the measurements at the "Pointe de Penmarc h" in September 1983, the DMS lifetime estimations obtained are reported in Table I. This method for determining chemical lifetimes can only be applied for local and intensive sources. The most critical point concerns the chemical relation between the various sulfur compounds which should be verified in order to validate these estimations. However, the other assumptions do not seem to have a significant influence on the lifetime estimation within an order of magnitude. 

From this, it can be seen that the amount of KOH within the hydroxide mixture would probably be critical in removing organo-sulfur from coal. While the particular role of KOH has not been determined, evidence from the literature has shown that the size of the cation may be important in stabilizing intermediate carbanions. Wallace et al. (J ) conducted a series of base- catalyzed, beta-elimination reactions with isopropyl sulfide and measured the amount of olefin production. The proposed mechanism involved initial abstraction of a proton by the t-butoxide base, and formation of a carbanion, with subsequent elimination of the sulfur moiety (which can be considered a good leaving group) to form the olefin (Equation 5). 

Cysteic acid is obtained in nearly quantitative yield from cysteine with aqueous hydrogen peroxide in the presence of iron(II) ions.397 Molybdates and tungstates have also been used as effective catalysts for similar transformations.398 An excellent route for the oxidation of 2-thioethanol to isothionic acid has been developed.399 Heteropolyoxometallates supported on alumina400 can also be used to oxidize a range of organo-sulfur compounds. For example, alkyl monosulfides to sulfoxides and sulfones, and thiols to sulfonic acids are a few possibilities (Figure 3.98). 

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