PREFERENCE FOR AN ION-NEUTRAL COMPLEX-MEDIATED PATHWAY OVER A 5-MEMBERED-RING H-SHIFT IN THE ISOMERIZATION OF CH3O-CENTER-DOT TO CH3CH2CH2OH+(CENTER-DOT) BY AB-INITIO THEORY(HCH2CH2)

Ab initio theory is used to explore whether the path from CH3OH+CH2CH2 . (1) to CH3CH2CH22OH+. (5) goes by way of a conventional 1,4-H shift to form . CH2OH+CH2CH3 (2), or via the ion-neutral complex-mediated H transfer [CH3OHCH2 = CH2](+.) (3) --> [(CH3CH2CH2OH+)-C-.] (4). Five l evels of theory all place the highest energy point in the complex-medi ated reaction 3 --> 4 slightly below that for the 1,4-H shift 1 --> 2, but both routes appear energetically feasible near the threshold far the dissociation of 1 to CH3CH2 + CH2 = OH+. Thus, 1 may take both pat hs to 5. It is concluded that when both a conventional and a complex-m ediated pathway seem plausible in a given system, the latter should be considered to be as likely as the former. Ab initio descriptions of o ther species involved in the isomerization of 1 to 2 also are presente d.