| The study and determination of rate constants for a specific chemicalreaction has always been one of the main research fields in chemistry. It is one of themost active subjects to predict the rate constants in different conditions theoretically. Inthis thesis, the typical Criegee radical CH2O2 and CH3CHO2 atmospheric chemistryreaction and radical amplifier chemistry water effect have been investigated with thetheory method. The reaction mechanism of CH2O2 and H2O, NO, CO in the atmospherehave been studied at the QCISD(T)/6-311+g(2d,2p)//B3LYP/6-311+G(2d,2p) andQCISD(T)/6-311G(d,p)//B3LYP/6-311G(d,p) level. The geometries for reactants, thetransition states and the products were completely optimized. All the transition states areverified by the vibration analysis and the intrisic reaction coordinate (IRC) calculation,provide the possible reaction route of every reaction. The result of study CH2O2+H2Ohave three channels: CH2O2+H2O→HMHP (R1),CH2O2+H2O→HCO+OH+H2O(R2) and CH2O2+H2O→HCHO+H2O2 (R3). R1 is the dominant reaction channel.By means of the POLYRATE program, the reaction rate constants with in 200-2000K are calculated the conventional transition-state theory (TST), the canonicalvariation transition-state theory (CVT) and with the small-curvature tunnelingcorrection (CVT/SCT) are applied to obtain the reaction rate constants. The resultsshow that the CVT/SCT rate constants at the QCISD/B3LYP level are in the bestunanimity with the experiment. At 298 K, calculate the rate constants of R1 is5.22×10-17cm3·molecule-1·s-1. The CH2O2 and NO reaction products are HCHO+NO2.At 298 K, calculate the rate constants is 4.38×10-15 cm3·molecule-1·s-1. The CH2O2 andCO reaction products are HCHO+CO2. At 298 K, calculate the rate constants is2.25×1015 cm3·molecule-1·s-1.Study the reaction mechanism of CH3CHO2 and H2O at CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p) level, The result of study indicates that reacting begins by twointermediate IM1a and IM1b, have six channels in all, the result has the formulationchannels HOCH3CHOOH, CH3CO, CH3CHO, HO, H2O2. No matter weather it wereconsidered from the viewpoint of kinetics or theromodynamics, its primary responsechannels for syn-HOCH3CHOOH and anti-HOCH3CHOOH result. Utilize Polyrate program to study the rate constants between 200-2000 K of the dominant reactionchannel. At 298 K, the rate constants are 1.14×10-16 and 6.23×10-19 cm3·molecule-1·s-1,respectively.Study radical amplifier chemistry chain propagation reaction HO2+NO in watervapor at the CCSD(T)/6-311G(d,p)//B3LYP/6-311G(d,p) level. The result of studyindicate that reactions HO2·H2O+NO mainly produces the molecule result HNO3+H2Oand HOONO+H2O. Product HNO3+H2O is the dominant reaction channel, is createsthe water effect the important reason. At 298 K, the rate constants of this reaction is2.51×10-12 cm3·molecule-1·s-1. Apply this rate constant to the mode while calculating,can fit in the water effect curve that the experiment gets well.The calculated results are fully compared with the experimental values, and theresults show that the DFT direct dynamics method is reliable and feasible. Wesuccessfully predicted the rate constants and activation energy for the reactions, andpredicted their temperature dependence for the reactions. This research provides auseful exploration for the dynamics study on the system with Criegee free radicals andradical amplifier chemistry water effect.
|
PDF Full Text Request