Loss of CO2 from Monodeprotonated Phthalic Acid upon Photodissociation and Dissociative Electron Detachment

E. J. MARCECA; JENNIFER A. NOBLE; CLAUDE DEDONDER-LARDEUX; CHRISTOPHE JOUVET

JOURNAL OF PHYSICAL CHEMISTRY A

AMER CHEMICAL SOC

Año: 2021

1089-5639

The decarboxylation (CO2 loss) mechanism of cold monodeprotonated phthalic acid was studied in a photodissociation action spectrometer by quantifying mass-selected product anions and neutral particles as a function of the excitation energy. The analysis proceeded by interpreting the translational energy distribution of the generated noncharged products, and with the help of quantum calculations. A particular result of this study reveals different fragmentation pathways in the deprotonated anion and in the radical generated upon electron photodetachment. Unlike the behaviour found in other deprotonated aryl carboxylic acids, which do not fragment in the anion excited state, a double loss of CO2 molecules takes place in the phthalic monoanion. Moreover, at higher excitation energies the phthalic monoanion experiences decarboxylative photodetachment with a statistical distribution of product translational energies, which contrasts with the impulsive dissociation reactions characteristic of other aryl carboxylic anions.