GAS-PHASE ION MOLECULE REACTIONS IN DILUTE MIXTURES OF DIMETHYL ETHER IN KRYPTON - BIMOLECULAR AND CLUSTERING REACTIONS

The results of high‐pressure variable‐temperature and variable ionizing electron energy studies of gas‐phase ion‐molecule reactions of dimethyl ether in krypton are presented. Near the ionization threshold a series of peaks corresponding to (CH3OCH3)nH+ (n = 1‐4) clusters are observed. At higher ionizing electron energies, two new series of peaks appear, corresponding to [CH3OCH2]+(CH3OCH3)n and [(CH3)3O]+ (CH3OCH3)n clusters. The onium ion, [(CH3)3O]+, has been previously reported at elevated temperatures under methane chemical ionization conditions. It was suggested that the onium ion is formed by reaction of (CH3)2OH+ with CH3OCH3 with subsequent elimination of methanel, i.e. by fragmentation of an adduct ion. The present results strongly suggest that, under our conditions, [CH3OCH2]+ rather than thermal (CH3)3OH+, is the precursor to [(CH3)3O]+. Copyright © 1990 John Wiley & Sons, Ltd.