Thiophene, sulfur

A review by Klemm and co-workers4 contains a brief but up-to-date discussion on the thiophene-forming reactions of hydrocarbons with sulfur. Thiophene itself is produced commercially by such a reaction more complex examples have been reported recently.21... 

Sulfur. Thiophene and benzo[ >] thiophene are both aromatic heterocycles, as discussed earlier in this review. Isothiazole is a planar molecule with an aromaticity comparable with those of thiazole and pyrazole, and higher than those of isoxazole and oxazole,122 140 as evaluated on the basis of Bird s aromaticity index A, based upon the statistical degree of uniformity of the bond orders of the ring periphery. Theoretical calculations and experimental data in connection with the aromaticity of isothiazole have been reviewed.141 Thiazole is also viewed as an aromatic molecule, similar to thiophene. It lacks an experimental aromaticity value, but the heat of formation together with bond lengths and angles have been calculated by various computational meth-... 

Coal Total Sulfur (wt %) Organic Sulfur (wt %) Aliphatic Sulfides Mercaptans Aromatic Sulfides (3) Mercaptans % of Organic Sulfur Thiophenic Heating value (BTU/lb) Pyrite (wt %)... 

Dimethametryn heterocyclic nitrogen, triazine Dimethazone see Clomazone Dimethenamid heterocyclic sulfur, thiophene, amide Dimethipin heterocyclic sulfur, dithiin, sulfone Dimethirimol heterocyclic nitrogen, pyrimidine Dimethoate phosphoro organic, phosphoro dithioate, amide... 

Tetradifon halogenated aromatic, sulfone Tetramethrin pyrethroid Tetrasul halogenated aromatic o,o,o, o -Tetrapropyl dithiopyrophosphate phosphoro organic, thiopyrophosphate Thenylchlon amide, heterocyclic sulfur, thiophene Thiabendazole heterocyclic nitrogen, benzimidazole, thiazole... 

The benzols are treated with sulfuric add or by catalytic hydrorefining to remove compounds containing sulfur (thiophene, mercaptans), oxygen (phenols) and nitrogen pyridine, cyanidesi. The refined product is then distilled to ield crude benzene containing the following hydrocarbons . ... 

Extrapolation of this dissociative mechanism to the prediction of isotope incorporation in heterocyclic molecules shows that the lone pair on the nitrogen atom (pyridine) or sulfur (thiophene) should again assist the formation of the respective transition states (16) and (17). Owing to this effect, ease of exchange in the positions in pyridine should be a > j8 > y. 

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