Negative Chemical Ionization Mass Spectrometric Studies on Dissociative Electron Attachment Processes of Chloroethylenes and Bromoethylenes

The temperature dependence of the formation of negative ions from chloroethylenes (cis-1,2-C2H2Cl2, trans-1,2-C2H2Cl2, C2HCl3, C2Cl3F, C2Cl4) and bromoethylenes (cis-1,2-C2H2Br2, trans-1,2-C2H2Br2, C2HBr3, 1,1-C2Br2F2) was studied using negative chemical ionization mass spectrometry. The halide ion was observed for all samples. Other fragment anions, (M-X)- (parent molecule, M, less one halogen atom, X)- and X2- were produced for some samples. The former was observed for trans-1,2-C2H2X2 and C2HBr3, and the latter for 1,2-C2H2Cl2, cis-1,2-C2H2Br2, and C2HBr3. The branching ratio of X2- and (M-X)- decreases with increasing the temperature. The branching ratio of X2- is considerably different for chloroethylenes and for bromoethylenes.