【作者】 赵燕；

【导师】 张庆竹；

【作者基本信息】 山东大学 ， 环境科学， 2009， 博士

【摘要】 挥发性有机化合物（Volatile Organic Compounds,VOCs）是大气对流层重要的痕量组分,其排放量巨大,种类繁多,而且结构多样,可与OH自由基、NO₃自由基及O₃等大气对流层中的重要的氧化性物质发生化学反应,生成醇、醛、酮、酸、酯等低挥发性的氧化性产物。这些产物的极性和水溶性增强,易通过成核、水合或吸附反应生成二次有机气溶胶（Secondary Organic Aerosol,SOA）。二次有机气溶胶粒子尺度小,平均寿命长,不仅会影响空气能见度和全球气候变化,而且严重威胁人类的健康。因此,研究挥发性有机化合物的大气氧化反应过程对于探讨区域及全球大气化学、气候变化和环境效应等都有非常重要的意义。本文采用密度泛函理论（Density Functional Theory,DFT）,对桧烯与O₃、β-丁香烯与O₃、正辛烷与OH自由基以及1-戊醇与OH自由基的大气氧化反应进行了系统的研究。详细分析了转化过程中各基元反应的势垒、焓变及自由能等物理化学参数,获得了一些有意义的研究结果,具体如下:（1）桧烯与O₃的大气反应本文从理论上研究了桧烯与臭氧的大气氧化反应机理。结果表明:桧酮、甲醛和甲酸是该反应体系的主要气相产物;实验上给出的3-氧代桧酮的气相形成机理是不合理的,本文给出了在大气环境中可以进行的反应通道;分子量为154的产物应为3-羟基桧酮而不是1-羟基桧酮;分子量为170的气相反应产物为2-异丙基-2-（2-氧代乙基）环丙烷羧酸和（2-甲酰-1-异丙基环丙基）乙酸的混合物;2-甲酰-1-异丙基环丙烷羧酸和1-异丙基环丙烷-1,2-二羧酸也是桧烯与臭氧气相反应的产物。在DFT计算给出的信息基础上,采用变分过渡态理论加小曲率隧道效应校正计算了桧烯与O₃的重要基元反应在200-400 K温度范围内的速率常数,并分析了反应途径的动力学性质。计算结果表明:对于桧烯与O₃的加成反应,隧道效应显著;理论得到的速率常数表现出较强的非阿仑尼乌斯（Arrhenius）行为,计算得到的变分过渡态加小曲率隧道效应（CVT/SCT）校正的速率常数与实验值符合的很好:速-温关系用三参数公式拟合为:k（T）=(2.49×10^-25)T^{（3.37）exp（-195.49/T）cm3 molecule-1 s-1。对于IM2的两个单分子分解反应（R（3）和R（4））,隧道效应都是可以忽略的。（2）β-丁香烯与O₃的大气反应本文在MPWB1K/6-31G（d）水平上研究了β-丁香烯与臭氧的大气氧化反应机理和氧化产物的结构。研究结果表明:β-丁香烯与臭氧的大气氧化反应的主要产物为4-[3,3-二甲基-2-（3-氧代丁基）环丁基]-4-戊烯酸、4-[3,3-二甲基-2-（3-氧代丁基）环丁基]-4-戊烯醛和甲醛;4-[2-（4-羟基-3-氧代丁基）-3,3-二甲基环丁基]-4-戊烯醛和7,11,11-三甲基-2-氧代双环[8.2.0]-6-十二碳烯-3-酮不是气相反应产物:对于实验上给出的产物4-[3,3-二甲基-2-（3-氧代丁基）环丁基]-4-戊烯酸的形成机理的研究结果表明从IM6到P1的通道是可行的;分子量为212的产物为1-羟基-β-丁香烯酮。（3）正辛烷与OH自由基的大气反应在B3LYP/6-31G（d）理论水平上对OH抽提正辛烷中C5位上的H引发的大气氧化反应通道进行了量子化学计算。计算结果表明:一级反应产物主要是1-丙基戊基硝酸酯、4-辛酮和7-羟基-4-辛酮;2-羟基-3-氧代-5-甲基-2-异丙基二氢呋喃和1-甲基-3-氧代丙基丁酸酯是二级反应的主要产物;4-辛烷氧基中间体与O₂的氧化反应是很容易发生的,它优于异构化反应以及单分子分解反应通道;对于中间体5-甲基-2-丙基-2-羟基四氢呋喃和2-甲基-5-异丙基-2,3-二氢呋喃之间的反应过程,反应开始时H₂O分子作为反应物参与反应,形成六元环以促使发生OH迁移,从而降低了反应的势垒,反应结束时又有H₂O分子生成。对整个反应来说H₂O分子起催化剂的作用。（4）1-戊醇与OH自由基的大气反应在B3LYP/6-31G（d）理论水平上研究了1-戊醇与OH自由基在大气中的氧化反应机理,得到了一些有价值的研究结果:β-羟基烷氧基中间体中C1-C2键断裂的分解反应的势垒比较低,仅仅0.37 kcal/mol,远远小于C2-C3键断裂的分解反应的势垒（8.54 kcal/mol）;3-羟基丙醛是}γ-羟基烷氧基的气相反应产物;δ-羟基烷氧基的异构化反应的势垒仅为1.79 kcal/mol,故该反应在大气环境中是容易发生的;由IM12及IM22的异构化反应（R（21）和R（26））势垒可知仲碳上的H比伯碳上的H更容易发生分子内迁移反应（异构化反应）。更多还原

【Abstract】 Volatile organic compounds（VOCs） are very important trace constituents of the troposphere.They have huge emissions and a wide range of structural diversities. They can be transformed by the chemical reactions with hydroxyl radical（OH）, nitrate radical（NO₃） radical and ozone（O₃）,and products are typically multifunctional low-volatile oxidation products containing aldehyde,ketone, organic acid,ester and alcohol moieties.Most of products in the atmosphere can contribute to the formation of secondary organic aerosol（SOA） through nucleation, hydration or absorption since their polarity and water-solubility are enhanced. Because of the small size,long average lifetime and adverse environment effects of SOA,they not only degrade air visibility,change global climate,but also are a severe threaten to human body.Therefore,the oxidation process investigation of volatile organic compounds in atmosphere is of great significance for exploring the regional and global atmospheric chemistry,climate change and environmental effects.In this thesis,a series of quantum chemical calculations based on density functional theory have been carried out to study several different atmospheric oxidation reaction systems（sabinene andβ-caryophyllene with ozone,n-octane and 1-pentanol with OH radical）.As a result,some significant progresses have been made,which can be described as follows:（1） Atmospheric reaction of sabinene with ozoneThe reaction mechanism of sabinene with ozone has been investigated systematically for the first time.The calculation results indicate that the main gas-phase products are sabina ketone,formaldehyde,and formic acid;The formation mechanisms of 3-oxo-sabina ketone provided by experiment are unreasonable and the more favorable pathway is found for the first time in this paper;The structure of product（molecular weight is 154） is just like 3-hydroxy sabina ketone but not 1-hydroxy sabina ketone;the compound（molecular weight is 170） can be found in gas phase and their structures are mostly due to 2-isopropyl-2-（2-oxoethyl）cyclopropane carboxylic acid and（2-formyl-1-isopropyl-cyclopropyl）acetic acid;2-formyl-1-isopropylcyclopropanecarboxylic acid and 1-isopropylcyclopropane-1,2- dicarboxylic acid do exist in gas phase.On the basis of density functional theory data,the kinetics calculations have been deduced using canonical variational transition state theory（CVT） with small-curvature tunneling correction method（SCT） over the temperature range of 200-400 K.Changes of geometries,generalized normal-mode vibrational frequencies,and potential energies along the reaction paths are discussed and compared.Studies show:the quantum tunneling effect are significant for the O₃ addition reaction with sabinene;the calculated rate constants exhibit typical non-Arrhenius behavior;the calculated CVT/SCT rate constants are in excellent agreement with the experimental values;The relationship of rate-temperature can be described as follows:k（T）=(2.49×10^-25)T^3.37exp（-195.49/T） cm³ molecule^-1 s^-1;For the two decompositions of IM2,the quantum tunneling effect can be neglected.（2） Atmospheric reaction ofβ-caryophyllene with ozoneThe O₃-initiated atmospheric oxidation reaction ofβ-caryophyllene is studied at the B3LYP/6-31G（d） level.The results show that 4-[3,3-dimethyl-2-（3-oxobutyl）-cyclobutyl]pent-4-enoic acid,4-[3,3-dimethyl-2-（3-oxobutyl）cyclobutyl]pent-4-enal, and formaldehyde are the primary gas-phase products;4-[2-（4-hydroxy-3-oxobutyl） -3,3-dimethylcyclobutyl]pent-4-enal and 7,11,11-trimethyl-2-oxabicyclo[8.2.0]dod-ec-6-en-3-one do not exist in the gas phase;The formation mechanisms of 4-[3,3-dimethyl-2-（3-oxobutyl）cyclobutyl]pent-4-enoic acid provided by experiment are investigated and the pathway from IM6 is feasible under general atmospheric conditions.The structure of product（molecular weight is 154） is just like 1-hydroxyl-β-caryophylla ketone but not 3-hydroxyl-β-caryophylla ketone.（3） Atmospheric reaction of n-octane with OH radicalsQuantum chemiscal calculations are carried out to study the OH-initiated atmospheric oxidation reaction of n-octane at B3LYP/6-31G（d） level.Several major conclusions can be drawn as follows:The main first generation products are 1-propylpentyl nitrate,4-octanone,and 7-hydroxy-4-octanone;2-hydroxy-3-oxo-5- methyl-2-propyldihydrofuran and 1-methyl-3-oxopropyl butyrate are the primary second generation products;the reaction of 4-octoxy intermediate with O₂ occurs easily in atmosphere,which is more favorable than the isomerization and decomposition reactions;for the formation of 2-methyl-5-propyl-2,3-dihydrofuran from 5-methyl-2-propyl-2-hydroxytetrahydrofuran,the participation of H₂O molecule results in the formation of a six-membered ring,which reduces the barrier of OH transfer.The behavior of H₂O indicates that it prefers an activator to a reactant.（4） Atmospheric reaction of 1-pentanol with OH radicalsThe reaction mechanism of 1-pentanol with OH radical is studied at the B3LYP/6-31G（d） level,which leads to the following valuable conclusions:the decomposition reaction ofβ-hydroxyalkoxy with the rupture of C1-C2 bond has a low potential barrier of 0.37 kcal/mol,which is much lower than that with the cleavage of C2-C3 bond（8.54 kcal/mol）;3-hydroxy-propanal is the gaseous product of the reactions ofγ-hydroxyalkoxy radical;The energy barrier of the isomerization ofδ-hydroxyalkoxy is just 1.79 kcal/mol,which means the process is favorable under atmospheric conditions;Comparing the energy barriers of R（21） and R（26） one can see that the isomerization involving H-atom abstraction from -CH₂- groups dominates over that from -CH₃ groups throughout the troposphere.更多还原