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Substituent and H/D randomization in the mass spectra of substituted diphenylacetylenic compounds
Author(s) -
Safe S.
Publication year - 1973
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210071205
Subject(s) - chemistry , substituent , mass spectrum , ion , fragmentation (computing) , polyatomic ion , protonation , medicinal chemistry , metastability , crystallography , stereochemistry , organic chemistry , computer science , operating system
The mass spectra of several substituted diphenylacetylenes are reported and the [metastable ion]/[daughter ion] ratios for the isomeric chloro‐ and bromodiphenylacetylenes suggested substituent scrambling in their respective molecular ions. The metastable ion data also indicated equilibration of the chloro substituents in a series of isomeric dichlorodiphenylacetylenes. In addition, the fragmentation patterns for the amino‐ and nitrodiphenylacetylenes differed somewhat from most other aromatic amino and nitro compounds. The aminodiphenylacetylenes fragment with expulsion of H 2 CN from the molecular ion and the expulsion of HCN from the [M – 1] + ion was only a relatively minor reaction. 4‐Nitrodiphenylacetylene loses NO from the molecular ion and OH from the [M – NO] + ˙, whereas the more familiar loss of OH from the molecular ion was not observed. The mass spectra of several deuterated substituted diphenylacetylenes clearly showed extensive (but not complete) H/D equilibration in the molecular ion or some subsequent decomposition ion. Comparative studies between 4‐chloro and 4‐bromo substituted biphenyl, diphenylacetylene and diphenyldiacetylene indicated similar degrees of H/D randomization, and the results showed that the CC group did not inhibit the proton equilibration between the two phenyl groups.