Sulfur compounds rings

Oxidation is the most general reaction of foreign compounds in animal species. It includes oxidation of alcohols, aldehydes, alkyl groups and sulfur compounds, ring hydroxylations, oxidative dealkylation and deamination of amines as well as dehalogenations. Some of these reactions are discussed in the following sections. 

The major part of the sulfur contained in crude petroleum is distributed between the heavy cuts and residues (Table 8.10) in the form of sulfur compounds of the naphthenophenanthrene or naphthenoanthracene type, or in the form of benzothiophenes, that is, molecules having one or several naphthenic and aromatic rings that usually contain a single sulfur atom. 

This reaction was first described by Gabriel in 1910 (40), when he warmed an acylaminoketone (197a) with an equimolecular amount of phosphorus pentasulfide. The reaction (Scheme 103) is similar to the preparation of other five-membered oxygen- and sulfur-containing rings from 1,4-dicarbonyl compounds. 

Substances that contain one or more atoms other than carbon as part of a nng are called heterocyclic compounds Rings m which the heteroatom IS oxygen nitrogen or sulfur rank as both the most common and the most important... 

In the FCC, HjS is formed principally by the catalytic decomposition of non-thiophenic (non-ring) sulfur compounds. Table 2-3 shows the effects of feedstock sulfur compounds on H2S production. 

Adding residue to the feed increases the sulfur content of coke proportional to the incremental sulfur in the feed (Table 2-6). Thiophenic (ring-type) sulfur compounds crack more slowly, and the uncracked thiophenes end up in gasoline, light cycle oil, and decanted oil. 

A useful comparison of the 13C shifts for acyclic and cyclic five- and six-membered sulfur compounds has been made86,220, but data on cyclic sulfur compounds of other ring sizes are rather limited. Typically, oxidation of sulfide to a sulfone results in 20-25 ppm... 

Several trends have emerged in the extensive carbon-13 NMR spectroscopy data that have been accumulated for sulfones and sulfoxides. Based on many studies of cyclic systems—particularly five- and six-membered ring sulfur compounds—these trends were shown to generally apply equally to both the cyclic and acyclic systems . Thus (a) oxidation of a sulfide to a sulfone results in a 20-25 ppm downfield chemical shift for sp -hybridized a-carbon atoms and 4-9 ppm upfield shift for / -carbons , and (b) there is very little difference between the chemical shifts of a-carbon atoms of sulfones and sulfoxides despite the difference in the inductive effects of these two functional groups . A difference is observed, however, in the H chemical shift of related cyclic sulfoxides and sulfones . 

Trickle-bed reactors are used in catalytic hydrotreating (reaction with H2) of petroleum fractions to remove sulfur (hydrodesulfurization), nitrogen (hydrodenitrogena-tion), and metals (hydrodemetallization), as well as in catalytic hydrocracking of petroleum fractions, and other catalytic hydrogenation and oxidation processes. An example of the first is the reaction in which a sulfur compound is represented by diben-zothiophene (Ring and Missen, 1989), and a molybdate catalyst, based, for example, on cobalt molybdate, is used ... 

Single-Ring Heterocyclic Sulfur Compounds Single-Ring Heterocyclic Sulfur Compounds Tetrachlorothiophene Sodium Strontium Sulfides, Disulfides Dimethyl Disulfide Dimethyl Sulfide Sulfides, Disulfides Sulfonic Acids Sulfonic Acids, Sulfoxides Sulfoxides... 

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