Banca de DEFESA: DIEGO DE OLIVEIRA ROGÉRIO
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.DISCENTE : DIEGO DE OLIVEIRA ROGÉRIO
DATA : 07/12/2021
HORA: 14:00
LOCAL: https://meet.google.com/sow-ywvv-kvd
TÍTULO:
Study of the electronic structure and the dissociative ionization dynamics induced by vacuum ultraviolet radiation of the 1,2-dichloropropane (C3H6Cl2) and chloroacetone (C3H5OCl) molecules
PÁGINAS: 237
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Físico-Química
ESPECIALIDADE: Espectroscopia
RESUMO:
The organochlorine compounds, among which the 1,2-dichloropropane and the chloroacetone molecules can be highlighted, display a great versatility of applications in chemical and pharmaceutical processes. The behavior of these compounds in the environment is of significant concern for the scientific community, since they can take part in the formation of secondary subproducts, which can be originated through the photoionization and photofragmentation processes and may play an important role in the dynamics of chemical reactions that take place in the atmosphere. In spite of the relevance of the given topic, only few studies concerning the behavior of these species when exposed to the electromagnetic radiation or their electronic structures are available in the literature. The developed project presents a strong interdisciplinary character and encompasses important experimental and theoretical branches of chemistry, allowing a better comprehension of fundamental properties of the species under study and a more justified discussion of the obtained results. Besides, the access and mastering of the several scientific branches involved in this work will serve as an important basis for new projects yet to be developed in the fields of spectroscopy and thermochemistry of molecular systems of scientific interest in the gas phase. Therefore, the present work is based on the investigation of the dissociative ionization dynamics and related properties of these molecular systems in the gas phase in the energy range of the vacuum ultraviolet radiation by employing the time-of-flight mass spectrometry coupled with the photoelectron-photoion coincidence spectroscopy and the synchrotron radiation, where the possible reactions leading to the fragmentation channels observed were proposed and discussed, as well as the theoretical study of the structural, electronic and thermochemical properties of the species observed by means of advanced computational methods. The theoretical results have shown that the isolated chloroacetone neutral molecule displays two conformational isomers, being the structure with the chlorine atom on the edge of a gauche/cis conformation with respect to the methyl group more stable in comparison with the trans conformation, as for the molecular cation, only the gauche conformation was found as a point of minimum on the potential energy surface. The analysis of the mass spectra has shown that the main photofragmentation channel in the energy range of 10.85 – 21.28 eV corresponds to the formation of the cation species at m/z=43. From the data available in the literature, the enthalpies of formation of the neutral molecule and its molecular cation have been derived by means of thermochemical routes as -207.8 ± 5.8 kJ/mol e 755.1 ± 6.8 kJ/mol., respectively. According to the theoretical results for the 1,2-dichloropropane, the most stable conformation of the isolated neutral molecule corresponds to the trans conformation involving the chlorine atoms, as the other stable structures present these atoms with the (+) gauche and (-) gauche conformations, as the molecular cation, besides from these configurations, presents the (+) near cis and (-) near cis isomers, being the latter regarded as the most stable structure. From the respective mass spectra, which were collected in the energy range from 11.26 to 21.56 eV, it was shown that the main dissociation channels of the 1,2-dichloropropane molecule led to the formation of the cation species at m/z=62, m/z=63 and m/z=76. Finally, a comparative analysis on the structures, properties and dissociation dynamics of both species was performed. The results obtained in this work may provide means for a better comprehension of the stability and reactivity of these species and serve as a model for the determination of photochemical and photophysical properties of similar halogenated and carbonyl compounds.
MEMBROS DA BANCA:
Presidente - Interno ao Programa - 2604704 - ALEXSANDRE FIGUEIREDO LAGO
Membro Titular - Examinador(a) Interno ao Programa - 1544394 - PAULA HOMEM DE MELLO
Membro Titular - Examinador(a) Externo à Instituição - ARNALDO NAVES DE BRITO - UNICAMP
Membro Suplente - Examinador(a) Interno ao Programa - 1864481 - HUEDER PAULO MOISES DE OLIVEIRA
Membro Suplente - Examinador(a) Externo ao Programa - 1600879 - REINALDO LUIZ CAVASSO FILHO