Styrene biological oxidation

Figure 15.10 Biological oxidation of styrene to (S)-styrene oxide.

PVAc, PVA and PVB homopolymers as well as the different copolymers mentioned above all have a similar chemical motif in common. They exhibit an all carbon-carbon single bond backbone, which needs to be broken at some point in a potential biodegradation mechanism. With respect to the backbone, poly(vinyl ester)s are closely related to poly(olefin)s, poly(styrene)s and poly(acrylate)s. These three are known not to be biodegradable. Instead, they usually decompose by the impact of UV radiation, oxidation and hydrolysis reactions, which are not considered to be biological degradation. 

Gonsidering that the chiral aldehydes obtained by asymmetric hydroformylation of vinylarenes are often oxidized to give the corresponding acids that exhibit biological activities, asymmetric hydrocarboxylation and its related reactions naturally attract much attention. Unfortunately, however, less successful work has not been reported on this subject than on the hydroformylation. Palladium(ii) is most commonly used for this purpose. Styrene and other vinylaromatics are most widely examined and the data for representative examples are summarized in Table 14. The products are of... 

Adducts to hemoglobin are perhaps the most useful means of biological monitoring by adduct formation. Hemoglobin is, of course, present in blood, which is the most accurate type of sample for biological monitoring. Adducts to blood plasma albumin are also useful monitors and have been applied to the determination of exposure to toluene diisocyanate, benzo(a)pyrene, styrene, styrene oxide, and aflatoxin Bj. The DNA adduct of styrene oxide has been measured to indicate exposure to carcinogenic styrene oxide.12... 

Exposure to styrene is the main occupational hygiene problem in reinforced plastics industry, where it is used as a crosslinking agent and solvent in unsaturated polyester resins. In addition, workers are exposed to acetone which is used as a clean-up solvent. Other solvents, such as methylene chloride, toluene, xylene, heptane (TLV 400 ppm, the Finnish OEL 300 ppm), methylcyclohexane (TLV and the Finnish OEL 400 ppm), and butyl acetate (TLV and the Finnish OEL 150 ppm) may also be used. Styrene is neurotoxic. Styrene is also a suspected carcinogen because it is metabolized via styrene-7,8-oxide. The TLV and the Finnish OEL of styrene is 20 ppm. Urinary mandelic acid concentration is the most common biological monitoring method for styrene. The ACGIH BEI is 800 mg/g creatinine and the FIOH BEI 3.2 mmol/1. 

Notably, the Dimroth rearrangement has been shown to occur in nature with the purine and pyrimidine bases of nucleosides and nucleotides upon exposure to certain chemical entities. For example, 3,4-epoxybutene, styrene oxide and other aromatic hydrocarbon based epoxides, butadiene and butadiene monoxide, chloroethylene oxirane, chlorambucil, and acrolein, " among others, have been shown to facilitate Dimroth rearrangement, and in some cases subsequent cross-linking of DNA. While interesting from a mechanistic and biological perspective, these reactions will not be reviewed here. 

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