| DOI | Trouver le DOI : https://doi.org/10.1016/S1387-3806(01)00409-2 |
|---|
| Auteur | Rechercher : Vedernikova, I.; Rechercher : Claeysa, M.; Rechercher : Salahub, D. R.; Rechercher : Casida, M. E. |
|---|
| Format | Texte, Article |
|---|
| Sujet | Alkali adducts; Collision-induced dissociation; Fatty acids; Theoretical calculations |
|---|
| Résumé | Theoretical calculations on Li+ and Na+ cationized methyl and n-butyl acetate, and methyl butyrate, were performed in order to explain the very different fragmentation behavior of Li+ and Na+ cationized fatty acid n-butyl esters in low-energy collisional activation. Li+ cationized n-butyl palmitate shows loss of 1-butene from the ester moiety, while the corresponding Na+ adduct does not reveal this loss. This elimination of 1-butene can be regarded as a McLafferty-type rearrangement and since it bears similarity with the well-known Norrish II photochemical rearrangement of ketones, involving an intramolecular γ-hydrogen transfer due to an excitation of the carbonyl bond, we postulated that an excitation of the Li+ cationized ester carbonyl bond in Li+ adducts of fatty acid n-butyl esters is the trigger for the loss of 1-butene in low-energy collisional activation. For the theoretical calculations using density-functional theory was considered because excited states can be treated by this approach. The results obtained on Li+ and Na+ cationized methyl and n-butyl acetate and methyl butyrate indicate that the inductive effect of Li+ is stronger than that of Na+ and that the ionic effect promotes less accumulation of negative charge on the carbonyl oxygen bound to Li+. The n → π∗ transition which is believed to be involved in McLafferty-type hydrogen rearrangement processes is shown to be energetically more favorable in Li+ complexes compared to Na+ complexes. This result is thus consistent with the experimental finding that loss of 1-butene occurs in Li+ complexes and not in the corresponding Na+ complexes of fatty acid n-butyl esters in low-energy collision-induced dissociation. |
|---|
| Date de publication | 2001-09-14 |
|---|
| Dans | |
|---|
| Langue | anglais |
|---|
| Publication du CNRC | Cette publication n’est pas du CNRCCe sont des publications qui ont été rédigées par un auteur du CNRC, mais avant que celui-ci soit employé du CNRC. |
|---|
| Numéro NPARC | 12338896 |
|---|
| Exporter la notice | Exporter en format RIS |
|---|
| Signaler une correction | Signaler une correction (s'ouvre dans un nouvel onglet) |
|---|
| Identificateur de l’enregistrement | 7981a840-df6c-4ddb-91b7-94fedff56a93 |
|---|
| Enregistrement créé | 2009-09-11 |
|---|
| Enregistrement modifié | 2020-03-27 |
|---|
