Theoretical Research Of Kemp Elimination Reaction And Its Mechanism

As an important kind of organic reactions, kemp elimination reaction in organic chemistry occupies an important position in organic chemistry, biochemistry, electrochemistry, chemical, pharmaceutical, and other aspects Benzoxazole commonly used in a number of additional infected material molecules, such as color film of a sense of the green sensitizer 1523, B114-3 and so on. Methyl-benzoxazole dye, pharmaceutical and other industrial organic synthesis intermediates and reagents important applications . PBO used for making films and fibers, etc.Back in the early twentieth century, someone has done Kemp Elimination Reaction of research, the study reported isoxazole derivatives rapid, irreversible decomposition of the formation of o-cyano-ketone or enol. In 1973, Casey and. Kemp reported benzoxazole based on the catalytic decomposition of the Kemp elimination reaction mechanism. In the same year, on the basis of catalytic decomposition of benzoxazole with the Bronsted linear relationship between the free energy has also been reported. In 1975, Kemp and Cox pairs of 3 -carbonic acid phenyl benzoxazole Decarboxylation of origin and to accelerate the rate of spontaneous dissolution reactions were also studied. At present, the Kemp elimination reaction of the reported number.Although the Kemp elimination reaction of a lot, but with the quantum chemistry calculation study also less. Having reviewed the literature on the basis, we plan to use quantum chemical calculation method and system studied in detail under the kemp elimination in alkaline catalytic reaction mechanism, including the search for reactants, products of the balance of the structure, vibrational frequencies, reaction transition state and reaction pathway , calculate the energy change in reaction, the reaction barrier, thermal kinetic parameters, as well as the activation energy at different temperatures, using transition state theory calculation of the reaction rate under different temperatures, allowing a detailed study under the conditions of alkaline catalysis, kemp elimination of the reaction mechanism.Specific studies include:1. The Kemp elimination reaction of benzoxazole:Using density functional theory (DFT) in the B3LYP method at 6-311 + G ** level, the first full-parameter optimization in gas phase benzoxazole isolated molecule, and its relationship with OH-formed complex configuration, and optimize the product of complex, the transition-state geometries, vibrational frequencies through the configuration of the calculation of the equilibrium configuration and the transition state structures for corroboration; by intrinsic reaction coordinate (IRC) analytic calculation to establish that the transition state and the reactants and the product of the correctness of the connection; Finally, from the perspective of the activation energy barrier of small molecules, allowing comparisons of catalytic performance. The results showed that: There is OH- involved in the reaction, the more isolated benzoxazole molecule decomposition ,Activation energy decreased significantly.2. The Kemp elimination reaction of nitro - benzoxazolylUsing DFT in the B3LYP method at 6-311 + G ** level, the first full-parameter optimization in gas phase nitro - benzoxazole (in the o-time because of the electron withdrawing ability of nitro too strong, resulting in the kinds of situations Under the transition state is difficult to find, so we have only studied the nitro in the right position between the bit and when the reaction mechanism) isolated molecules and their complexes formed by OH-configuration, and optimizing the product of complex, transition state conformation , through the configuration of the calculation of vibrational frequencies of equilibrium geometries and transition state structures for corroboration; by the intrinsic reaction coordinate (IRC) analytic calculation to establish that the transition state and the reactants and products connected to the correctness; and finally,From the perspective of the activation energy barrier OH- to make note of catalytic performance. The results showed that: There is OH- involved in the reaction, the activation energy significantly reduced, 6 - nitro - benzoxazolyl than the 5 - nitro - benzoxazolyl activation energy reduction ranges from great.3. The Kemp elimination reaction of chloro-- benzoxazolylUsing DFT in the B3LYP method at 6-311 + G ** level, the first full-parameter optimization of chlorine-based gas - benzoxazolyl isolated molecules and their complexes formed by OH- configuration, and optimize the product of complex materials, transition-state geometries, vibrational frequencies through the configuration of the calculation of the equilibrium configuration and the transition state structures for corroboration; by intrinsic reaction coordinate (IRC) analytic calculation to establish that the transition state and the reactants and products connected to the right sex; Finally, from the perspective of the activation energy barrier OH- make a note of catalytic performance. The results showed that: There is OH- involved in the reaction, the activation energy significantly lower activation energy reduction ranges from:6 - chloro - benzoxazole >5 - chloro– benzoxazole>7 - chloro - benzoxazole >4 - chloro - benzo-oxazole4. The Kemp elimination reaction of methyl - benzoxazolyl:Using DFT in the B3LYP method at 6-311 + G ** level, the first full-parameter optimization of chlorine-based gas - benzoxazolyl isolated molecules and their complexes formed by OH- configuration, and optimize the product of complex materials, transition-state geometries, vibrational frequencies through the configuration of the calculation of the equilibrium configuration and the transition state structures for corroboration; by intrinsic reaction coordinate (IRC) analytic calculation to establish that the transition state and the reactants and products connected to the right sex; Finally, from the perspective of the activation energy barrier OH- make a note of catalytic performance. The results showed that: There is OH- involved in the reaction, the activation energy significantly lower activation energy reduction ranges from:7 - methyl - benzoxazolyl >5 - methyl– benzoxazolyl> 4 - methyl - benzoxazolyl >6 - methyl - benzo-oxazole.All theoretical calculations of this work are carried out by using the GAUSSIAN-03 program package.