ISSN:
0030-493X
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The mass spectra of benzenephosphonic and benzenephosphonous acids are readily observable under normal operating conditions and, at low sample temperatures (50 to 85°C), the 70 eV electron-impact degradations are characteristic. The phosphonic acid shows peaks for the molecular ion at 158 amu and for characteristic degradation fragments at 141 (C6H5PO2H), 94 (C6H6O), 78 to 7 (C6H6, C6H5), 65 (H3PO2, C5H5), 51 (C4H3), 47 (PO) and 39 (C3H3) amu. Above 120°, however, and after a pressure surge indicative of a thermal dehydration in the sample, a peak at 420 amu associated with the cyclic, trimeric anhydride, (C6H5PO2)3, is observed along with a characteristic set of fragment peaks at 373, 357, 343, 327, 280, 262, 233, 216 and 199 amu, whose interrelations are summarized in Scheme 1. The phosphonous acid, at 75°C and at 70 eV, shows peaks for the molecular ion at 142 amu and for characteristic degradation fragments at 124 (C6H5PO), 111 to 107 (C6H5PH ± 2H), 94 (C6H6O), 78 to 7 (C6H6, C6H5), 65 (H3PO2, C5H5), 51 (C4H3), 47 (PO) and 39 (C3H3) amu. The phenylphosphine is apparently formed by rearrangement in the excited state after electron-impact rather than by thermal disproportionation in the sample as the latter requires the formation of relatively more of the phosphonic acid than is observed. At higher sample temperatures (120°C) somewhat increased amounts of the phosphonic acid, presumably formed by partial disproportionation in the sample, are observed. Accurate mass assignments and broad metastables confirm the postulated fragmentation processes.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/oms.1210050606
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