Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2017-05-30T17:17:07Z No. of bitstreams: 1 2015 - Than?zia Ferraz Santos.pdf: 1742658 bytes, checksum: 07706cbaaa52be04cb7ec04d0d453fa2 (MD5) / Made available in DSpace on 2017-05-30T17:17:07Z (GMT). No. of bitstreams: 1 2015 - Than?zia Ferraz Santos.pdf: 1742658 bytes, checksum: 07706cbaaa52be04cb7ec04d0d453fa2 (MD5) Previous issue date: 2015-08-28 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPq / In this work, potential energy surfaces for the reactions of hydroxyl radical and 2,5-dimethylfuran were studied using the Density Functional Theory. The stationary points, such as reactants, pre-barrier complex, transition states and products were located at BHandHLYP/aug-cc-pVDZ and M06-2X-cc-pVDZ levels by geometry optimization, followed by the calculations of vibrational frequencies. Single point calculations using CCSD(T) were also explored. Thermodynamics properties of enthalpy, entrophy and Gibbs free energies have been determinated at 298,15 K within the conventional equations of Statistical Thermodynamics. The results suggest different addition mechanisms, since an analysis of the potential energy surface (PES) in BHandHLYP/ aug-cc-pVDZ points to paths going through a pi-type intermediary, while in M06-2X/aug-cc-pVDZ the intermediary would have a sigma-type interaction. About the abstraction reactions, only the PES obtained in M06-2X/aug-cc-pVDZ level points to the formation of a pre-barrier complex. The rate coefficients have been determined on the basis of the Variational Transition State Theory, with the kcvt program. The coefficient obtained at CCSD(T)/aug-cc-pVDZ//BHandHLYP/aug-cc-pVDZ for the mechanism which includes the participation of ?-PC is ???????=48,4?10?11, cm? molec-1 s-1, approximately 4 times higher than the experimental rate coefficient. Deviations of this magnitude are considered satisfactory in theoretical calculation of kinetic parameters. Addition of OH should be the main degradation pathway for furan and its derivatives, during daytime. Moreover, it was possible to clarify the effect of the formation of pre-barrier complexes in the reactions between DMF and OH radicals and propose rate coefficients in the high temperature region, which can be applied in combustion studies / Neste trabalho, as superf?cies de energia potencial para as rea??es do radical hidroxila (OH) com o 2,5-dimetilfurano (DMF) foram estudadas em detalhes, utilizando a Teoria do Funcional de Densidade. Pontos estacion?rios como reagentes, complexos pr?-barreira, estados de transi??o e produtos foram localizados por procedimentos de otimiza??o de geometria, acompanhado do c?lculo das frequ?ncias vibracionais, em n?veis BHandHLYP/aug-cc-pVDZ e M06-2X/aug-cc-pVDZ. C?lculos single point a partir da metodologia coupled-cluster com simples e duplas excita??es com tratamento perturbativo das triplas conectadas, CCSD(T), tamb?m foi explorado. Propriedades termodin?micas de entalpia, entropia e energia livre de Gibbs foram calculadas a 298,15 K atrav?s das equa??es da Termodin?mica Estat?stica. Os resultados sugerem mecanismos de adi??o diferentes, j? que uma an?lise da superf?cie de energia potencial (SEP) em BHandHLYP/aug-cc-pVDZ aponta para caminhos passando por um intermedi?rio do tipo pi, enquanto em M06-2X/aug-cc-pVDZ o intermedi?rio seria do tipo sigma. Na abstra??o, apenas a SEP obtida em M06-2X/aug-cc-pVDZ aponta para a forma??o de um intermedi?rio pr?-barreira. Coeficientes de velocidade foram determinados com base na Teoria do Estado de Transi??o Variacional, com aux?lio do programa kcvt. O coeficiente CCSD(T)/aug-cc-pVDZ//BHandHLYP/aug-cc-pVDZ para o mecanismo que inclui a participa??o do ?-PC ? de ???????=48,4?10?11 cm? molec-1 s-1, superestimado em rela??o ao coeficiente experimental em aproximadamente 4 vezes. Desvios dessa magnitude s?o esperados em c?lculos te?ricos, especialmente quando envolvem mol?culas volumosas. Pode-se constatar que a adi??o de OH deve ser a principal rota de degrada??o para o furano e seus derivados durante o dia. Al?m disso, foi poss?vel esclarecer o efeito da forma??o de intermedi?rios pr?-barreira nas rea??es entre DMF e o radical OH.