Structures and Chemical Rearrangements of Benzoate Derivatives Following Gas Phase Decarboxylation.
J Am Soc Mass Spectrom
; 33(10): 1914-1920, 2022 Oct 05.
Article
em En
| MEDLINE
| ID: mdl-36084146
ABSTRACT
Decarboxylation of carboxylate ions in the gas phase provides a useful window into the chemistry displayed by these reactive carbanion intermediates. Here, we explore the species generated by decarboxylation of two benzoate derivatives 2-formylbenzoate (2FBA) and 2-benzoylbenzoate (2BBA). The nascent product anions are transferred to a cryogenic ion trap where they are cooled to â¼15 K and analyzed by their pattern of vibrational bands obtained with IR photodissociation spectroscopy of weakly bound H2 molecules. The structures of the quenched species are then determined by comparison of these spectra with those predicted by electronic structure calculations for local minima on the potential energy surface. The 2-phenide carbanion generated by decarboxylation of 2FBA occurs in two isomeric forms that differ in the orientation of the formyl group, both of which yield a very large (â¼110 cm-1) redshift in the stretching frequency of the H2 molecule attached to the anionic carbon center. Although calculated to be a local minimum, the analogous 2-phenide species could not be isolated upon decarboxylation of 2BBA. Rather, the anionic product adopts a ring-closed structure, indicating efficient nucleophilic attack on the pendant phenyl group by the nascent phenide. The barrier for ring closing is evaluated with electronic structure calculations.
Texto completo:
1
Bases de dados:
MEDLINE
Idioma:
En
Revista:
J Am Soc Mass Spectrom
Ano de publicação:
2022
Tipo de documento:
Article
País de afiliação:
Estados Unidos