Degradation sulfones

Reactions other than those of the nucleophilic reactivity of alkyl sulfates iavolve reactions with hydrocarbons, thermal degradation, sulfonation, halogenation of the alkyl groups, and reduction of the sulfate groups. Aromatic hydrocarbons, eg, benzene and naphthalene, react with alkyl sulfates when cataly2ed by aluminum chloride to give Fhedel-Crafts-type alkylation product mixtures (59). Isobutane is readily alkylated by a dipropyl sulfate mixture from the reaction of propylene ia propane with sulfuric acid (60). 

Carbamates such as Aldicarb undergo degradation under both aerobic and anaerobic conditions. Indeed the oxidation of the sulfur moiety to the sulfoxide and sulfone is part of the activation of the compound to its most potent form. Subsequent aerobic metaboHsm can completely mineralize the compound, although this process is usually relatively slow so that it is an effective iasecticide, acaricide and nematocide. Anaerobically these compounds are hydrolyzed, and then mineralized by methanogens (61). 

Sulfones have been prepared by three principally different strategies One-component methods include various isomerizations, rearrangements under degradation, and hydrolysis of oxygen-substituted dialkyl (diaryl) sulfuranes(VI). 

Bowmer and Bowden75 studied the radiation degradation of poly-2-methyl-l-pentene sulfone and found that at low radiation doses the S02/olefin ratio is 2 1, however at high doses this ratio is decreased and is close to unity. Thus the oligomerization of the olefin, which is the cause for the discrepancy between G(S02) and G(olefin), appears to be reversible. 

The main reaction in the radiation degradation of all the polyfolefin sulfone)s is the depropagation step... 

FIGURE 8. Overall reactions scheme for radiation degradation of poly(olefin sulfone)s. Reproduced by permission of the authors from Reference 74. 

However, Pacansky and his coworkers77 studied the degradation of poly(2-methyl-l-pentene sulfone) by electron beams and from infrared studies of the products suggest another mechanism. They claim that S02 was exclusively produced at low doses with no concomitant formation of the olefin. The residual polymer was considered to be essentially pure poly(2-methyl-l-pentene) and this polyolefin underwent depolymerization after further irradiation. However, the high yield of S02 requires the assumption of a chain reaction and it is difficult to think of a chain reaction which will form S02 and no olefin. 

Bowden and Thompson83 studied the degradation of thin films of various poly(olefin sulfone)s of low olefins due to radiolysis by electron beams at 20 °C. All samples decreased in thickness, indicating scission and depropagation. 

When comparing secondary alkanesulfonates (SAS) and linear alkylbenzene-sulfonates (LAS), it is obvious that SAS are more readily degraded than LAS. This is somewhat more pronounced at lower temperatures (Table 34). 

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