title: Electron ionisation and fast-atom bombardment mass spectrometry study of diaryl carbonates.
abstract: Electron ionisation mass spectrometry studies were performed previously for p-diphenyl carbonate and some monosubstituted diphenyl carbonates. In this work, p-diphenyl carbonate and p-methoxyphenylphenyl carbonate are re-examined, and p-chlorophenyl phenyl carbonate and two disubstituted diphenyl carbonates, bis (p-chlorophenyl) carbonate and p-methoxyphenyl-p-fluorophenyl carbonate, are studied for the first time. The previously established fragmentation routes were observed for all compounds investigated. Some other different sequences were observed, and a fragmentation path, other than decarboxylation, of the molecular ion is proposed. In the fast-atom bombardment study it was observed that the M(+*)/[MH](+) ion abundance ratio increased from 0.44 for compound 1 to 2.95 for compound 5. [MH](+) is not a dominant ion in most of compounds studied, in spite of the presence of a carbonyl group, a strong proton acceptor. The presence of two oxygen atoms bonded to the carbonyl group appears to induce delocalisation of the electron pairs, thus deactivating the carbonyl site for protonation. In addition, m-nitrobenzyl alcohol (NBA) being a relatively aprotic/hydrophobic matrix reinforces the deactivation for protonation. Because the carbonate group and NBA are common features to the study, the contributions of the substituents were taken into account to explain the different behaviour of the five compounds with respect to protonation.
authors.affiliation: Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Edifício C8, Campo Grande, 1749-016 Lisboa, Portugal.
authors.forename: Vitor
authors.initials: V
authors.lastname: Pinto
authors.forename: Fátima
authors.initials: F
authors.lastname: Norberto
authors.forename: Teresa
authors.initials: T
authors.lastname: Pamplona
authors.forename: M Tereza
authors.initials: MT
authors.lastname: Fernandez
authors.forename: M Filomena
authors.initials: MF
authors.lastname: Duarte
mesh_terms: D002254:Carbonates / Q000032:analysis* / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D002254:Carbonates