Study On Enol Cyclization Reaction Based On C-H Activation And Hydrogenation Degradation Of Pesticides

Carbon-Hydrogen bond?C-H?is one of the most common and simple chemical bonds in the organic compounds.By the transformation of C-H bond,chemists can construct several other chemical bonds successfully,such as C-C,C-O,C-N,C-S,etc.However,the transformation of C-H bond is not easy to implement because of its high bond energy and low reactivity.Comparing with traditional methods,the direct C-H activation transformation has shown greater advantages.By this way,the prefunctionalization of substrates is not needed,so the synthetic steps and the waste emissions are both reduced.At present,there are two common patterns of direct C-H activation,one is transition-metal catalyzed C-H activation,the other is C-H activation through radical processes.In this thesis,with the aiding of certain experimental method,theoretical study was conducted to explore the detailed mechanism of several C-H activation reactions.The research contents are as follows:1.A DFT study on rhodium???-catalyzed C-H functionalization of o-vinylphenols with alkynes: regioselectivity and chemoselectivityA molecular mechanism of rhodium???-catalyzed C-H functionalization of o-vinylphenols with alkynes has been investigated with DFT calculations.The results suggest the whole reaction is comprised with four stages:?I?O-H deprotonation,?II?C-H activation induced by Rh???catalyst interacting with o-vinylphenols,???alkyne coordination and?IV?regeneration of Rh???catalyst.The C-H activation step proceeds under the concerted metalation deprotonation mechanism.The regioselectivity and chemoselectivity of the reaction also have been studied respectively.The regioselectivity for different C-H activation sites is depended on the coordination structure of the related Rh???complex.When the substrates are substituted with alkyl?or alkenes?at the terminal position of the alkene,such as?E?-2-?prop-1-en-1-yl?phenol and 2-allylphenol,the apparent activation energies??G?are obvious higher than that of o-vinylphenols,which indicates that they are unfavorable to occur.The effect of CO2 Me substituent on the para position to the hydroxyl is also investigated.The calculated results would provide useful information for chemists to deeply understand the Rh???-catalyzed C-H functionalization reactions and to design new high selectivity catalysts.2.Theoretical and experimental study on the degradation mechanism of atrazine in Fenton oxidation treatmentThe residues of atrazine in surface and ground water will cause harm to human health as they are slowly biodegraded microbiologically.In this work,Density Functional Theory?DFT?and the Polarizable Continuum Model?PCM?were used to investigate the degradation of atrazine in the aqueous medium by Fenton oxidation technology.The results show that H atom abstraction pathways are more probable than both OH-radical addition and Cl atom substitution pathways.Moreover,the H atom abstraction from the –CH– of –CH?CH₃?₂ group and –CH₂– of –CH₂CH₃ group are expected to occur more easily.New dealkylation and alkyl oxidation mechanisms are proposed,in which water can act as a catalyst to reduce the reaction barrier dramatically.The stable intermediates and products: CH₃COCH₃,DEDIA,DIA,DEA,CAFT,CDAT,CDET,CDFT and CFIT,have been identified with LC/MS analysis.This study offers a cost-effective way to probe the degradation mechanism of atrazine in the aqueous medium by Fenton oxidation technology.3.Mechanism for OH-Initiated Degradation of Levofloxacin in aqueous-phaseAdvanced oxidation methods is one of the most efficient water treatment methods to treat levofloxacin.Using high OH-radicals oxidation activity and oxidation reduction potential can effectively remove the antibiotics in the water.Research on OH-radicals' degradation of levofloxacin helps to provide more accurate data to support advanced oxidation technology.We calculate the Ozzie and Harriet addition of levofloxacin and oxidation degradation respectively,finding out the optimal degradation path.