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Positive molecular ions and ion‐neutral complexes in the gas phase: Structure and stability of C 2 H 4 O 2 +· and C 2 H 4 O 2 2+ isomers
Author(s) -
Fantuzzi F.,
Baptista L.,
Rocha A. B.,
BoechatRoberty H. M.
Publication year - 2012
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.24181
Subject(s) - chemistry , ion , molecule , gas phase , crystallography , formate , computational chemistry , organic chemistry , biochemistry , catalysis
The structure and stability of several C 2 H 4 O 2 +· and C 2 H 4 O 2 2+ isomers were studied by quantum chemical methods in an attempt to elucidate their most stable molecular arrangements and infer their contribution to the ion chemistry of astrophysical environments. The geometry optimizations were performed at B3LYP/6‐311G** and MP2/6‐311G** level. Single‐point calculations at equilibrium geometries were performed at left eigenstate completely renormalized coupled cluster method, CR‐CCL(2,3). Ninety minimum structures for the ions at the MP2 level were found: 38 related to C 2 H 4 O 2 +· , 33 to C 2 H 4 O 2 2+ , and 19 to ion‐neutral complexes. The more stable C 2 H 4 O 2 +· isomers have enolic structures, in agreement with the McLafferty rearrangement mechanism of straight chain aliphatic acids. In contrast, the most stable C 2 H 4 O 2 2+ isomer has an acyclic OCCO nonplanar linear chain structure, with terminal + OH 2 and CO + linkages. In addition, acetic acid and methyl formate analogue structures were found only for the monopositive ion, with higher energies though. Both global minima are significantly different from the more stable neutral isomers and, therefore, could not be found in a geometry optimization procedure starting from the neutral structures. Dissociative recombination reaction pathways of C 2 H 4 O 2 +· and its application to the formation of astrophysical neutral molecules are also discussed. © 2012 Wiley Periodicals, Inc.