The mass spectrometry of DT-and monosubstituted biphenyls: Dependence of fragmentation patterns on position of substitution

Mass spectra of the oxygenated products generated from phenanthrene under simulated environmental conditions

The photooxidation of phenanthrene under stimulated environmental conditions to 9,10-epoxy-9,10-dihydrophenanthrene, among other oxygenated products, serves as a model for the conversion of polycyclic aromatic hydrocarbons to potentially mutagenic and/or carcinogenic products. The separation and identification were achieved by glass capillary gas chromatography mass spectrometry, and by comparison of gas chromatographic retention times and mass spectral fragmentation patterns with data observed for authentic samples obtained independently through synthesis or from commercial sources. The structural rearrangements of 2,2'-di-substituted biphenyls such as 2-formyl biphenyl-2'-carboxylic acid, 2,2' diformyl biphenyl and diphenic acid anhydride, induced upon electron impact are investigated and discussed in detail. The mass spectral comparison of 9,10-epoxy-9,10-dihydrophenanthrene, a primary mammalian metabolite of phenanthrene, and certain other structural isomers was conducted and the results of this study suggest a mass spectral technique capable of differentiating arene oxides from oxepin, phenol and carbonyl isomers. A discussion of the potential impact of the sensitized photooxidation of more condensed environmental polycyclic aromatic hydrocarbon pollutants is presented and the role of bioactive arene oxides produced under such photooxidation conditions is also discussed. Related oxides of polycyclic aromatic hydrocarbons are known to be proximate carcinogens and/or mutagens generated by metabolic activation. The role and significance of solar induced oxidation in the weathering of petroleum hydrocarbons at air-sea interfaces and the incorporation of potentially bioactive organic residues in the food chain are also addressed.

The effect of ortho substitution on the mass spectral fragmentation of polychlorinated biphenyls

Isomeric chlorinated biphenyls are observed to yield very similar mass spectra, rarely exhibiting a [M - Cl]+ fragment of any significant magnitude. However, those isomers containing three ortho chloro substituents display a relatively intense [M - Cl]+ fragment. A rationalization for this observation is put forth on the basis of the relative stabilities of both product and reactant.