Mecanismos de fragmentação iônica da r-carvona produzidos pelo impacto de elétrons com baixas energias

Abstract

In this work, the ionic fragmentation of R-carvone (C10H14O) from electron impact was studied. R-carvone is a molecule presents in large quantities in peppermint (Menta Spicata) and which has several applications in the health area, highlighting its potential in the treatment against the cancer. The experimental measurements of the cations formation produced by the electron impact on the R-carvone molecule were carried out, using a Hiden Quadrupole Mass Spectrometer (EPIC 300), in the mass region of 1-151 amu , with resolution of 1 u.m.a.. The mass spectrum, recorded for incident electron energy of 70 eV, was placed in absolute scale, revealing cross sections of 103 different formed cations, by direct or dissociative ionization of R-carvone. The number of fragments recorded in this spectrum was much higher than that observed in previously reported studies using electron impact, most likely due to the higher mass resolution of our spectrometer.The relative abundances of the formed cations compare reasonably well with the corresponding values reported in the literature. Individual partial ionization cross sections (PICS) for 78 cations recorded with high intensities in the mass spectrum were measured for the first time in this work, to the best of our knowledge, in the electron impact energy regions of their formation thresholds up to 100 eV. Total ionization cross sections (TICS) of R-Carvone were also obtained for the first time in this work. Furthermore, appearance energies (AEs) and Wannier exponents (ps) were determined for 38 of the cationic fragments observed in the mass spectrum, 36 of them for the first time in the literature. From the data generated in this work, it was possible to propose several mechanisms of ionic fragmentation and molecular structural ionic fragmentation mechanisms for R-carvone, correlating them with the values of AEs and PICS profiles.