INFIQC   05475
INSTITUTO DE INVESTIGACIONES EN FISICO- QUIMICA DE CORDOBA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Theoretical study of linear Perfluoroalkyl Peroxynitrates CxF2x+1OONO2, from x= 2 to 4. DFT and RRKM calculations
Autor/es:
ADRIANA G. BOSSOLASCO; MAXIMILIANO A. BURGOS PACI; GUSTAVO A. ARGÜELLO; FABIO E. MALANCA *
Lugar:
Carlos Paz
Reunión:
Congreso; 13th Conferencia Latinoamericana de Fisico-Química Organica (CLAFQO-13); 2015
Resumen:
p { margin-bottom: 0.1in; direction: ltr; color: rgb(0, 0, 0); line-height: 120%; widows: 2; orphans: 2; }p.western { font-family: "Calibri",sans-serif; font-size: 11pt; }p.cjk { font-family: "Batang","바탕",serif; font-size: 11pt; }p.ctl { font-family: "Times New Roman",serif; font-size: 11pt; }a:link { color: rgb(0, 0, 255); }Peroxynitrates(ROONO2)are formed in the degradation of volatile organic compounds emittedto the atmosphere and are important because they act as reservoirs ofNO2and ROOradicals.Industrial compounds such as chlorofluorocarbons (CFCs),hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), andhydrofluoroethers (HFEs) lead to the formation of fluorinatedperoxynitrates. For example, compounds such as HCFC-225ca(C2F5CHCl2),HFC-227a (C3F7H)and HFC-329p (C4F9H)could lead to the formation of C2F5OONO2,C3F7OONO2and C4F9OONO2,respectively.Inthis work we used DensityFunctional Theory (DFT) to evaluate the ground-state geometricparameters, vibrational frequencies, and the relative populations ofthe different conformers of each peroxynitrate. These parameters werecalculated using the hybrid density functional B3LYP with the6-311+G* basis set, using the G09 program package in conjunction withGaussView 5.0. Thermal rate coefficients and their pressuredependence for the unimolecular decomposition of these peroxynitrateswere evaluated by standard RRKM theory implemented in the UNIMOLprogram.Fourdifferent conformers are found in the Potential Energy Surface (PES)for C3F7OONO2and C4F9OONO2.A qualitative inspection of the PES shows that interconversionbetween them could involve trajectories needing less than 4 kcal, andthat the relative energies are less than 1.8 kcal mol−1with respect to the more stable conformer. On the other hand, forC2F5OONO2two different minima are found, with 0.016 Kcal for theinterconversión energy between them, so it is expected anappreciable amount of both conformers at room temperature.Themost interesting parameters in peroxynitrates are the X-O−O−Ndihedral and the O−Ndistance. Previous studies show that the dihedral is around 105° forthis kind of peroxynitrates 1.The calculated value of this parameter is 104.5° for C2F5OONO2and 104.7º for C3F7OONO2and C4F9OONO2.The N−Odistance, extremely long in peroxynitrates, takes values of 1.56 Åfor this family.RRKMcalculation for the thermal decomposition rate constant show a goodagreement with the reported experimental values 2,3.The dependence of the rate constant with the pressure decreases withthe length of the carbon chain for pressures higher than 1 mbar. Forpressures lower than 1 mbar the dependence with the length of thecarbon chain is reversed.