Premium
Substituent effects on ion abundances and energetics in substituted acetophenones
Author(s) -
Chin Margaret S.,
Harrison A. G.
Publication year - 1969
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.1210021106
Subject(s) - substituent , ion , chemistry , fragmentation (computing) , ionization , mass spectrum , molecule , polyatomic ion , crystallography , analytical chemistry (journal) , stereochemistry , organic chemistry , computer science , operating system
Based on the quasi‐equilibrium theory of mass spectra it is shown that the intensity ratio [A] + /[M] + , where [A] + is a fragment ion and [M] + is the molecular ion, is given by [A] + /[M] + = f′ (k 1 /k t ) ((1/f) − 1), where f is the fraction of molecular ions with insufficient energy to fragment, f′ is the fraction of [A] + ions with insufficient energy to fragment, and k 1 /k t is the fraction of fragmenting molecular ions which form [A] + . For substituted acetophenones it is shown that f depends on the substituent present and that f′ k 1 /k t is also substituent dependent for formation of both [CH 3 CO] + and [YC 6 H 4 CO] + . It is also shown that no direct information concerning the effect of a substituent on the rate of a particular fragmentation reaction can be obtained from intensity studies. The ionization potentials of the parent molecules and the appearance potentials of the [YC 6 H 4 CO] + fragment ions have been measured for fifteen substituted acetophenones and the correlations with substituent constants are discussed.