Ge Maofa

The CH3N Diradical: Experimental and Theoretical Determinations of the Ionization Energies

Pyrolysis of CH3 N3 under the protection of NO generates a continuous methylnitrene CH3 N diradical beam that enables the ionization energies of different ionic states of the CH3 N diradical to be determined by HeI photoelectron spectroscopy (PES; see spectrum) and both ab initio and density functional theory (DFT) calculations. The ab initio and DFT results are in excellent agreement with the PES experiment and show that the CH3 N diradical has C3v symmetry and the ground state of the CH3 N radical cation is the (2) E state.

First experimental observation on different ionic states of the CH3SS radical: A HeI photoelectron spectrum

A continuous flowing CH3SS radical beam is produced in situ by pyrolysis of CH3SSCH3 at 215(±0.5) °C. An obvious and complete photoelectron (PE) spectrum of the CH3SS radical is recorded in situ for the first time. Five sharp peaks at 8.63, 9.36, 9.94, 10.29, 10.72 eV and one broader band at 11.82 eV are observed in the PE spectrum below 12 eV. The first peak with the lowest ionization energy, 8.63 eV, is attributed to removal of an electron from the highest occupied molecular orbital (HOMO) 5a″ of the CH3SS radical, corresponding to the CH3SS+(X 1A′)←CH3SS(X 2A″) ionization. The vibrational spacing 600±60 cm−1 on the first peak corresponds to the S–S stretch mode excited in the CH3SS+ cation upon photoionization process. The sharp peaks at 9.36 and 9.94 eV come from removal of the electron from the 16a′ orbital, leading to 3A″ and 1A″ ionic states of the CH3SS radical, and the sharp peaks at 10.29 and 10.72 eV should be the result of removal of the electron from the 15a′ orbital of the CH3SS radical. To ...

Rate Constants for the Gas Phase Reactions of Ozone with Diethylamine and Triethylamine

Kinetics of the reactions of ozone with diethylamine (DEA) and triethylamine (TEA) were investigated in a self鄄made Teflon chamber. Experiments were conducted under pseudo鄄first鄄order decay conditions using excess DEA and TEA. Cyclohexane was added to the reactor to quench OH radicals. At (298依1) K and 1.01伊105 Pa, the measured absolute rate constants were (1.33依0.15)伊10-17 cm3·molecule-1·s-1 for DEA and (8.20依1.01)伊10-17 cm3·molecule-1·s-1 for TEA. Comparing our results with data for the reactions of analogous amines with ozone, we propose that the amines react with ozone probably through an electrophilic reaction mechanism. In addition, the reactions of trialkylamines with ozone are all much faster than those of dialkylamines with ozone, which may explain the intriguing finding in several field studies where higher concentrations of dialkylammonium were detected in aerosol samples. The atmospheric lifetimes of DEA and TEA were also estimated based on the measured rate constants and the ambient tropospheric concentration of ozone, which indicates that the reaction with ozone is an important loss pathway for these amines in the atmosphere, especially in polluted areas.

Evaluation and Application of Dual-Reactor Chamber for Studying Atmospheric Oxidation Processes and Mechanisms

A new smog chamber with dual reactors was designed and constructed to study atmospheric oxidation processes that may form ozone or secondary organic aerosols (SOAs). The chamber consists of two 5 m(3) fluorinated ethylene propylene (FEP) Teflon-film reactors housed in a thermally isolated enclosure, in which the temperature can be well controlled in the range of -10 to 40 degrees C. The influence of the light source on the gas-phase oxidation mechanism of propene was investigated. The results showed that multiple ultraviolet (UV) light sources were better than traditional narrow-band black-lamp light sources. Preliminary experiments on propene and m-xylene photo-oxidation processes were performed. The results showed that the dual-reactor chamber can simulate the gas-phase oxidation processes that form ozone or SOAs, and can be used to determine the effects of various species by comparing experiments performed using different initial concentrations. The SOA yield data from m-xylene photo-oxidation under different NOx conditions were in good agreement with those from previous studies. This proves that the chamber can simulate gas-to-particle conversion processes. The dual reactors have the advantage of enabling experiments to be performed with only one key parameter being changed. This will help us to further understand the role of key factors in complex atmospheric pollution processes.

The diradical (CH3)2CHN and its isomeric molecule (CH3)2C=HN: Generation and characterization

A continuously flowing (CH3)2CHN beam is generated by pyrolysis of (CH3)2CHN3 at 113(±0.5)°C using normal inlet system with an 8 mm bore of the exit of the quartz tube under the presence of molecular sieve (30 A) and stabilizing NO gas, and its HeI photoelectron (PE) spectrum is also recorded in situ. A spectrum recorded further away from the pyrolysis catalyst or by using a 0.4 mm bore of the quartz tube is the PE spectrum of (CH3)2C=NH, which comes from the isomerization of (CH3)2CHN. The ionization energies of (CH3)2CHN and (CH3)2C=NH are determined for the first time by the photoelectron spectroscopy experiment, and Gaussian 2 and improved density functional theory calculations. Experimental and theoretical results agree reasonably well, and show that (CH3)2CHN is a diradical with Cs symmetry and has a 3A″ ground state, and (CH3)2C=NH is a closed shell molecule with Cs symmetry.

Synthesis, spectra, structure and quantum chemistry study on two novel oxovanadium complexes with hydrotris (pyrazolyl) borate ligands

Two novel oxo-vanadium complexes of VO(HB(pz)3)(pzH)(SCN) (1) and VO(HB(3,5-Me2pz)3) (3,5-Me2pzH)(SCN)(SCNH)2 (2) with tris(pyrazolyl) hydroborate ligands were prepared by the reaction of VOSO4·nH2O, KSCN with Na(HB(pz)3), pyrazole, or Na(HB(3,5-Me2pz)3) and methyl-substituted pyrazole in the solution of MeOH, respectively. The complexes were characterized by element analysis, IR, and UV-vis spectra. In the mean time, the fluorescence spectrum was studied too, and the result indicates that the luminescence of the complexes is related to the interaction between oxovanadium ion and tris(pyrazolyl) hydroborate ligands. In addition, structures of oxovanadium complexes 1 and 2 were determined by X-ray diffraction. The electronic structures and the bonding characters of the two complexes were analyzed with ab initio calculations.

Electronic structure and conformation properties of halogen-substituted acetyl acrylic anhydrides, CX3C(O)OC(O)CH═CH2 (X = H, F, or Cl).

Acetyl acrylic anhydride (CH(3)C(O)OC(O)CHCH(2)) and its halogen-substituted derivatives (CF(3)C(O)OC(O)CHCH(2) and CCl(3)C(O)OC(O)CHCH(2)) were prepared by the heterogeneous reaction of gaseous CH(2)═CHC(O)Cl with CX(3)C(O)OAg (X = H, F, or Cl). The molecular conformations and electronic structure of these three compounds were investigated by HeI photoelectron spectroscopy, photoionization mass spectroscopy, FT-IR, and theoretical calculations. They were theoretically predicted to prefer the [ss-c] conformation, with each C═O bond syn with respect to the opposite O-C bond and the C═C bond in cis orientation to the adjacent C═O bond. The experimental first vertical ionization potential for CH(3)C(O)OC(O)CHCH(2), CF(3)C(O)OC(O)CHCH(2), and CCl(3)C(O)OC(O)CHCH(2) was determined to be 10.91, 11.42, and 11.07 eV, respectively. In this study, the rule of the conformation properties of anhydride XC(O)OC(O)Y was improved by analyzing the different conformations of anhydrides with various substitutes.

Heterogeneous Processes between Secondary Photochemical Oxidants and Aerosols

A wide range of gaseous and particulate phase pollutants are emitted into the atmosphere by routes like external or internal combustion,evaporation,eolian and others.Once released into the atmosphere,these primary emissions are dispersed,transported and,at the same time,transformed by various chemical processes that determine their ultimate environmental fate.The secondary products of these processes are more important ones concerning their effects on human health and the quality of the environment,which represent the critical property determining the establishment of certain air standards and regulatory policies.The prevalence of tropospheric photooxidants is of international concern because of their adverse effects on human health and environment.A lot of nitrogen oxides(NOx) and volatile organic compounds(VOCs) have been emitted from natural and factitious sources,and then transform into secondary photochemical oxidants by the atmospheric oxidation reactions,contributing to atmospheric oxidation capacity and climate change patterns.The formation of secondary photochemical oxidants including ozone(O3),gaseous nitric acid(HNO3),hydrogen peroxide(H2O2) and peroxy acetyl nitrate(PAN) is driven by hydroxyl radical(OH) during the daytime whose main sources are photolysis of O3 and nitrous acid(HONO).At night,the nitrite radical(NO3) substitutes OH radical and plays the most important role in the nighttime atmospheric chemical processes.However,the more complicated situation is that aerosol particles are ubiquitous in the Earths atmosphere.As reactive surfaces they can take part in the heterogeneous reactions with secondary photochemical oxidants.It changes the tropospheric composition and the properties of the gaseous reactants,making the atmosphere pollution even more serious.It also alters the properties of aerosols like hygroscopicity and influences the radiation balance by the direct and indirect effects.Thus,many efforts have been made to this subject,which has become one of focuses of the atmospheric chemical research currently.In order to make clear the intricate coupling effect between secondary photochemical oxidants and aerosol particles,laboratory simulation is basic.Aerosol samples produced in the laboratory or collected in the atmosphere are selected and put into the reactor such as flow tube,Knudsen cell or aerosol chamber,which react with the secondary photochemical introduced.The kinetics processes and products can be detected by the equipment involving mass spectrometry(MS),Fourier transform infrared spectrometry(FTIR),diffuse reflectance infrared Fourier transform(DRIFTS) and aerosol mass spectrometry(AMS),which are connected to the reactors.Chromatography and surface characterization techniques also can be applied to detect the heterogeneous reaction as the off-line methods.Laboratory researches about heterogeneous kinetic and mechanism are of importance to understand this coupling effect,which could contribute to comprehending the field observed events and provide the basic parameters to model forecast.Research on heterogeneous reactions of secondary photochemical oxidants is challenging.However,there are some aspects that are not clear,and more studies are needed.First,the researches mainly concentrate on the O3 and HNO3 heterogeneous reactions,while less about others.The data must be enriched through the future studies.Second,the reaction system often has isolated secondary photochemical oxidant and individual particles,which is not consistent with real atmospheric composition.It leads certain error between the results from laboratory simulation and field observation.Last but not least,no commercial equipment is applicable to this area.Researchers must establish high-precision and sensitive apparatuses to detect the transformation of reactants under atmospheric conditions.In this review,the formation of secondary photochemical oxidants is introducesd and the recent international laboratory researches and state of the art with regard to this area are concluded.In the end the main scientific problems are put forward,and the prospect is made.

A novel heterogeneous reaction for generating gaseous nitrous acid

The short-lived reactive specimen nitrous acid HONO was generated in the gas phase by the heterogeneous reaction of gaseous HCI with AgNO2 which can generate higher concentration of HONO than other methods. We investigated the process from generation to dissociation in the gas phase under different controlled temperatures, and discussed the ionization and reaction on the solid surface by combination of the photoelectron spectroscopy and photoionization mass spectroscopy (PES-PIMS) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS).

Synthesis, Structure and Non-thermal Decomposition Kinetics of Scorpionates Oxovanadium Complexes with Carboxyl Acid Ligand

Two new oxovanadium complexes with poly(pyrazolyl)borate and carboxylic acid as ligands,VO [phCH_2CH (NH_2)COO][HB(pz)_3] (1) and VO(3,5-Me2pz)[HB(3,5-Meapz)_3](CH_3COO) (2),were synthesized successfully.The two complexes were characterized by IR,elemental analyses,thermal analyses,and single crystal X-ray diffraction.The study of non-isothermal decomposition kinetics for complex 1 showed that the possible reaction mechanisms of the two steps were nucleation and growth with n=1/4,and chemical reaction,respectively;the kinetic equations may be expressed as dα/dT=(A/β)e~(-ElRT)(1/4)(1-α)[-ln(1-α)]~(-3) and dα/dT=(A/β)e~(ElRT)(1-α)~2,respectively,the apparent activation energies of the steps are 223.52 and 331.94 kJ·mol~(-1),respectively,the pre-exponentials ln(A/s~(-1)) are 49.67 as well as 57.50. The study of non-isothermal decomposition kinetics for complex 2 showed:the possible reaction mechanisms of the two steps were chemical reaction,and nucleation and growth with n=1/2,respectively,the kinetic equations may be expressed as dα/dT=(A/β)e~(-ElRT)(1-α)~2,and dα/dT=(A/β)e~(-ElRT)(1/2)(1-α)[-in(1-α)]~(-1),respectively,the apparent activation energies of the steps were 300.56 and 444.72 kJ·mol~(-1),respectively,the pre-exponentials In(A/s~(-1)) were 75.53 as well as 92.50.