Chemical ionization mass spectrometry studies—VII: Deuterium labeled decanes

CI mass spectra of the five isomeric vicinal d 2 ‐decanes have been recorded using methane and d 4 ‐methane as reagent gases. In contrast to earlier suggestions, we find that a large fraction of the alkyl fragment ions from n ‐decane are formed by elimination of olefins from the abundant [M – 1] ion. Only the C 9 and C 8 fragment ions are produced completely by a one‐step reaction between the decanes and the methane reagent ions. Isotope exchange does not occur between the hydrocarbon and the reagent ions derived from d 4 ‐methane but extensive scrambling of the deuterium label in the d 2 ‐decanes does take place in the [M – 1] ion.