Relative reactivities of polyhalofluoroalkanes toward bromophilic or chlorophilic attacks have been evaluated for the first time by comparing the rates of halophilic attacks by a carbanion derived from the addition of...Relative reactivities of polyhalofluoroalkanes toward bromophilic or chlorophilic attacks have been evaluated for the first time by comparing the rates of halophilic attacks by a carbanion derived from the addition of a nucleophile to an olefin with the rate of β-elimination of the same carbanion intermediate. Relative reactivity orders of some polybromofluoroalkanes and polychlorofluoroalkanes are CF_2Br_2>CF_3CFBr_2 ～ CF_2BrCF_2Br>CF_3CBr_3, and CCl_4 > CF_3CCl_3 > CF_2ClCCl_3 > CFCl_3 > CFCl_2CFCl2 ～ CF_2ClCFCl_2. Early transition states for halophilic attacks are speculated.展开更多
A polymer-supported palladium-imidazole catalyst was used to catalyze the hydrogenation of various olefins under mild conditions. The rate of hydrogenation was studied. The effects of factors such as substrate concent...A polymer-supported palladium-imidazole catalyst was used to catalyze the hydrogenation of various olefins under mild conditions. The rate of hydrogenation was studied. The effects of factors such as substrate concentration,catalyst concentration,partial pressure of hydrogen and temperature on initial rate of reaction of selected olefins were investigated. A mechanism for the reaction was proposed from the rate equation. The effects of the solvent and structure of the olefin on the rate of hydrogenation were investigated. The catalyst showed good reusability without any leaching of metal from the support. The homologous analog of the polymer-supported catalyst could not be used as catalyst for the hydrogenation of olefins in methanol because there was precipitation of the metal during reaction.展开更多
A series of emission reduction measures were conducted in Wuhan,Central China,to ensure good air quality during the 7th Military World Games(MWG)in October 2019.To better understand the implications for ozone(O_(3))po...A series of emission reduction measures were conducted in Wuhan,Central China,to ensure good air quality during the 7th Military World Games(MWG)in October 2019.To better understand the implications for ozone(O_(3))pollution control strategies,we applied integrated analysis approaches based on the de-weathered statistical model,parameterization methods,chemical box model,and positive matrix factorization model.During the MWG,concentrations of O_(3),NO_x,and volatile organic compound(VOCs),OFP(O_(3)formation potential),L_(OH)(OH radical loss rate)were 83μg/m^(3),43μg/m^(3),26 ppbv,188μg/m^(3),and 3.9 s^(-1),respectively,which were 26%,18%,3%,15%,and 13%lower than pre-MWG values and 6%,39%,30%,33%,and 50%lower than post-MWG values,respectively.After removing meteorological influence,O_(3)and its precursors during the MWG decreased largely compared with post-MWG values,and only O_(3),NO_(2),and oxygenated VOCs(OVOCs)declined compared with pre-MWG values,which revealed the emission reduction measures during the MWG played an important role for O_(3)decline.For six VOCs sources,the mass contributions of biomass burning and solvents usage during the MWG decreased largely compared with pre-MWG values.O_(3)production was sensitive to VOCs and the key species were aromatics,OVOCs,and alkenes,which originated mainly from solvents usage,biomass burning,industrial-related combustion,and vehicle exhaust.Decreasing O_(3)concentration during the strict control was mainly caused by OVOCs reduction due to biomass burning control.Generally,the O_(3)abatement strategies of Wuhan should be focused on the mitigation of high-reactivity VOCs.展开更多
文摘Relative reactivities of polyhalofluoroalkanes toward bromophilic or chlorophilic attacks have been evaluated for the first time by comparing the rates of halophilic attacks by a carbanion derived from the addition of a nucleophile to an olefin with the rate of β-elimination of the same carbanion intermediate. Relative reactivity orders of some polybromofluoroalkanes and polychlorofluoroalkanes are CF_2Br_2>CF_3CFBr_2 ～ CF_2BrCF_2Br>CF_3CBr_3, and CCl_4 > CF_3CCl_3 > CF_2ClCCl_3 > CFCl_3 > CFCl_2CFCl2 ～ CF_2ClCFCl_2. Early transition states for halophilic attacks are speculated.
基金Supported by University Grants Commission,Government of India
文摘A polymer-supported palladium-imidazole catalyst was used to catalyze the hydrogenation of various olefins under mild conditions. The rate of hydrogenation was studied. The effects of factors such as substrate concentration,catalyst concentration,partial pressure of hydrogen and temperature on initial rate of reaction of selected olefins were investigated. A mechanism for the reaction was proposed from the rate equation. The effects of the solvent and structure of the olefin on the rate of hydrogenation were investigated. The catalyst showed good reusability without any leaching of metal from the support. The homologous analog of the polymer-supported catalyst could not be used as catalyst for the hydrogenation of olefins in methanol because there was precipitation of the metal during reaction.
基金supported by the National Key Research and Development Program of China (No.2022YFE0136100)the National Natural Science Foundation of China (No.41505133,41775162,and 42061130215)+1 种基金the Royal Society Newton Advanced Fellowship (No.NAFR1201354)the Beijing Major Science and Technology Project (No.Z211100004321006)。
文摘A series of emission reduction measures were conducted in Wuhan,Central China,to ensure good air quality during the 7th Military World Games(MWG)in October 2019.To better understand the implications for ozone(O_(3))pollution control strategies,we applied integrated analysis approaches based on the de-weathered statistical model,parameterization methods,chemical box model,and positive matrix factorization model.During the MWG,concentrations of O_(3),NO_x,and volatile organic compound(VOCs),OFP(O_(3)formation potential),L_(OH)(OH radical loss rate)were 83μg/m^(3),43μg/m^(3),26 ppbv,188μg/m^(3),and 3.9 s^(-1),respectively,which were 26%,18%,3%,15%,and 13%lower than pre-MWG values and 6%,39%,30%,33%,and 50%lower than post-MWG values,respectively.After removing meteorological influence,O_(3)and its precursors during the MWG decreased largely compared with post-MWG values,and only O_(3),NO_(2),and oxygenated VOCs(OVOCs)declined compared with pre-MWG values,which revealed the emission reduction measures during the MWG played an important role for O_(3)decline.For six VOCs sources,the mass contributions of biomass burning and solvents usage during the MWG decreased largely compared with pre-MWG values.O_(3)production was sensitive to VOCs and the key species were aromatics,OVOCs,and alkenes,which originated mainly from solvents usage,biomass burning,industrial-related combustion,and vehicle exhaust.Decreasing O_(3)concentration during the strict control was mainly caused by OVOCs reduction due to biomass burning control.Generally,the O_(3)abatement strategies of Wuhan should be focused on the mitigation of high-reactivity VOCs.
