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1.
Torsional states caused by vibrations of hydroxyl groups in the methanediol molecule and its two deuterated analogues – DO(CH2)OH and DO(CH2)OD were analysed at MP2/cc-pVTZ and CCSD(T)/cc-pVQZ levels of theory. In the first case, 2D PES and 2D surfaces of kinematic coefficients were calculated with geometry optimisation for all other geometric parameters, and in the second case, only the energy of optimised configurations at the MP2/cc-pVTZ level of theory was determined. Then 2D PES was recounted to the complete basis set (CBS) limit by extrapolating the results of calculations at the MP2/cc-pVTZ and MP2/cc-pVQZ levels of theory The calculated values were then averaged over four equivalent points on the coordinate plane. Hamiltonian matrices were constructed using DVR and Fourier methods. After their subsequent diagonalization, the energies of the stationary torsional states were computed. Their classification by C2V(M) and CS(M) molecular symmetry groups has been performed. The splitting values due to the tunnelling of the thirty most deeply located torsional states in the three studied molecules were also determined. The torsional states, internal rotation barriers, and tunnelling frequencies in the molecules of methanediol and hydrogen trioxide were compared.  相似文献   

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通过荧光光谱实验和理论计算对金属离子在乙醇溶液中的微团簇结构进行了研究。荧光光谱实验发现在275~330 nm范围存在较强的乙醇分子荧光峰,当加入盐离子(Zn~(2+))后该处荧光强度逐渐变弱,说明盐的加入对乙醇体系的荧光效率产生了影响,破坏了原有乙醇分子之间的作用,使得其刚性结构发生改变,荧光效率降低,同时Zn~(2+)与乙醇分子通过溶剂化作用形成了新的微团簇,在350~380 nm之间出现了新峰。通过对团簇结构[Zn-(H_2O)_n]~(2+)(n=1~3)进行优化比较,得到了相对精确及运算成本较低的密度泛函理论B3LYP方法,并应用于Zn~(2+)在乙醇溶液中团簇结构计算。结果表明体系的第一溶剂化层存在着n=1~6的微团簇分子,且最多为6。比较理论计算荧光光谱与实验荧光光谱,进一步说明了Zn~(2+)与乙醇形成了新的微团簇及计算方法的可行性。  相似文献   

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Sulfide alkoxy radicals are important intermediates during the partial oxidation of alkyl sulfides in atmospheric chemistry and in combustion. The atmospheric reaction sequence to formation of the alkoxy radicals includes (1) initial reaction with OH to create a radical on a carbon site, (2) the carbon radical then associates with 3O2 to form a peroxy radical, and (3) an NO radical reacts with the peroxy radical to form an alkoxy radical (RO?) plus NO2. This study determines structural parameters, internal rotor potentials, bond dissociation energies, and thermochemical properties (ΔfH°, S°, and Cp(T)) of 3 corresponding alcohols HOCH2SCH2CH3, CH3SCH(OH)CH3, and CH3SCH2CH2OH of methyl ethyl sulfides studied in order to characterize the thermochemistry of the respective alkoxy radicals. The lowest energy molecular structures were calculated using the B3LYP density functional level of theory with the 6‐311G(2d,d,p) basis set. Standard enthalpies of formation (Δf298) for the radicals and their parent molecules were calculated using B3LYP/6‐31 + G(2d,p), CBS‐QB3, M062x/6‐311 + g(2d,p), and G3MP2B3 methods. Isodesmic reactions were used to determine ?fH° values. Internal rotation potential energy diagrams and rotation barriers were investigated using the B3LYP/6‐31 + G(d,p) level theory. The contributions for S°298 and Cp(T) were calculated using the rigid rotor harmonic oscillator approximation based on the structures and vibrational frequencies obtained by CBS‐QB3 calculations, with contributions from torsion frequencies replaced by internal rotor contributions. Group additivity and hydrogen bond increment values were developed for estimating properties of structurally similar and larger sulfur‐containing peroxide molecules and their radicals.  相似文献   

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The acetyl-protected, thiol-terminated ethers AcS(CH(2))(4)O(CH(2))(4)SAc and AcS(CH(2))(2)O(CH(2))(2)O(CH(2))(2)SAc have been synthesised, and a range of related scanning tunnelling microscopy (STM)-based methods have been employed to fabricate and electrically characterise gold | single molecule | gold junctions involving these molecules. The single-molecule conductance values obtained are consistently found to be substantially higher (by a factor of 2-3) than the conductances of analogous alkanedithiols of similar length (HS(CH(2))(9)SH and HS(CH(2))(8)SH, respectively). A rationalisation of these findings is suggested, namely that the lone pair electrons on the oxygen atoms are substantially closer in energy to the Fermi energy of the gold leads than are the occupied and unoccupied states of methylene chains, so that the ether oxygens behave in a manner analogous to 'wells' in a double-tunnelling-barrier system. In agreement with this suggestion, the current-voltage behaviour of the monoether can be fitted using the Simmons approach, and the barrier height is found to be significantly lower than for alkanedithiols of approximately the same length.  相似文献   

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Ni2(OCH3)2/SiO2催化剂上CO2和CH3OH的吸附和反应性能   总被引:1,自引:0,他引:1       下载免费PDF全文
采用表面改性和离子交换相结合的方法制备了Ni2 (OCH3 ) 2 /SiO2 负载型双核金属甲氧基配合物催化剂 ,利用红外光谱 (IR)、程序升温脱附 (TPD)、程序升温表面反应 (TPSR)和微反技术考察了催化剂的表面结构以及CO2 和CH3 OH的化学吸附和反应性能 .结果表明 :Ni2 (OCH3 ) 2 /SiO2 中Ni2 + 与载体SiO2 表面O2 -以双齿配位形式键合 ,甲氧基以桥基形式联结双金属离子形成双核物种Ni2 (OCH3 ) 2 ;CO2 在催化剂表面存在甲氧碳酸酯基物种和桥式两种吸附态 ,CH3 OH则只有一种分子吸附态 ;在 10 0~ 2 0 0℃条件下 ,CO2 和CH3 OH在催化剂上的反应产物主要是DMC和H2 O ;根据反应结果 ,讨论了催化反应机理 .  相似文献   

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The addition reaction of CH2OO + H2O CH2(OH)OOH without and with X (X = H2CO3, CH3COOH and HCOOH) and H2O was studied at CCSD(T)/6-311+ G(3df,2dp)//B3LYP/6-311+G(2d,2p) level of theory. Our results show that X can catalyse CH2OO + H2O → CH2(OH)OOH reaction both by increasing the number of rings, and by adding the size of the ring in which ring enlargement by COOH moiety of X inserting into CH2OO···H2O is favourable one. Water-assisted CH2OO + H2O → CH2(OH)OOH can occur by H2O moiety of (H2O)2 or the whole (H2O)2 forming cyclic structure with CH2OO, where the latter form is more favourable. Because the concentration of H2CO3 is unknown, the influence of CH3COOH, HCOOH and H2O were calculated within 0–30 km altitude of the Earth's atmosphere. The results calculated within 0–5 km altitude show that H2O and HCOOH have obvious effect on enhancing the rate with the enhancement factors are, respectively, 62.47%–77.26% and 0.04%–1.76%. Within 5–30 km altitude, HCOOH has obvious effect on enhancing the title rate with the enhancement factor of 2.69%–98.28%. However, compared with the reaction of CH2OO + HCOOH, the rate of CH2OO···H2O + HCOOH is much slower.  相似文献   

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《Composite Interfaces》2013,20(8):757-774
Nano-sized Zn(OH)2 was synthesized by the co-precipitation method. Further, the structure and properties were tested with FTIR, UV-visible spectroscopy, XRD and TGA as analytical tools. The structural morphology and size of the Zn(OH)2 synthesized by the co-precipitation method were determined by using FESEM and HRTEM techniques. The effect of the synthesized nano-sized Zn(OH)2 on the structural and thermal properties of PVA matrix was tested and discussed.  相似文献   

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通过控制前驱体中乙醇与水的体积比,采用溶剂热法得到不同形貌的Bi2WO6纳米片,探讨了Bi2WO6形貌与光致发光性能之间的关系。Bi2WO6的结晶度、纳米片的棱长以及片层间距随醇水比增大而逐渐提高,当醇水比为1∶1时,Bi2WO6纳米片的棱长、片层间距和比表面积(BET)最大,表现出优异的光致发光性能;而在醇水比大于1∶1时,纳米片的棱长、片层间距和BET随之降低,光致发光性能继而减弱。以上表明醇水比为1∶1时,复配乙醇与水协同修饰Bi2WO6纳米片形貌的效果最佳,BET最大,从而促进其光致发光性能的改善。  相似文献   

14.
Volatile organic compounds (VOCs) play a major role in the physical and chemical process of the tropospheric chemical reactions in both polluted and remote environments. A theoretical work has been presented on the VOC of allyl alcohol with O3 molecule is investigated using density functional theory methods. The reaction profile is initiated through the cycloaddition of ozone which leads to the formation of primary ozonide with minimal relative energy barrier of 1.31 kcal/mol which decomposes to form carbonyl molecule and carbonyl oxide. Carbonyl oxide, i.e. criegee intermediates reacts with various atmospheric species to produce more hazardous and toxic end products to the environment. The condensed form of Fukui function was calculated to predict reactive sites of the primary and secondary reaction profile. The rate coefficient using CVT with SCT over the temperature range of 258–358K is analysed and also to study the atmospheric effects of allyl alcohol in the atmosphere. The predicted rate coefficient for the favourable reaction pathway of kp1 found to be 1.190 ×10?15 cm3/molecule/sec and comparable with the experimental result at 298 K. The atmospheric lifetime of allyl alcohol was found to be around 10 hours in addition to that global warming potentials are compared with the CO2.  相似文献   

15.
CH2Cl与OH自由基反应机理的理论研究   总被引:4,自引:0,他引:4  
用量子化学从头算方法对CH2 Cl与OH自由基反应生成HCCl+H2 O、HCOCl+H2 和H2 CO +HCl的机理进行了研究 .在UMP2 (FC) / 6 311++G 水平上计算出了各物种的优化构型、振动频率 ;并在Gaussian 3(G3)水平上计算了他们的零点能 (ZPE)、相对能量及总能量 .结果表明 ,CH2 Cl和OH自由基反应首先经无垒过程生成一个富能中间体CH2 ClOH ,中间体再经过一系列原子转移、基团旋转和键断裂分别生成产物HCCl+H2 O、HCOCl+H2 和H2 CO +HCl;三者均为放热反应 ,放热量分别为 72 .81、338.5 4和 35 4 .0 8kJ/mol;生成H2 CO +HCl放出的热量比生成HCCl+H2 O放出的热量多 2 81.2 7kJ/mol,与实验结果吻合 .  相似文献   

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ABSTRACT

A direct dynamic study on the reactions of CH3O2?+?CH2O was carried out over the temperature range of 300–1500?K. All stationary points were calculated with the M06-2X/6-311++G(d,p) level of theory and identified for local minimum. The energetic parameters were refined at QCISD (T)/cc-pVTZ and CCSD (T)/cc-pVTZ levels of theory. Three channels were explored and a reaction of hydrogen abstraction from CH2O by CH3O2 was identified as dominant channel which involves the formation of a prereactive complex in the entrance channel. The rate coefficient of the dominant channel was calculated with TST and TST/Eck and the Eckart tunnelling effect is only important over the lower temperature region. The calculated rate coefficient of the dominant channel has positive temperature dependence and agrees reasonably with the available literature data.  相似文献   

19.
In this article, the isomerisation mechanisms of HN(NO2)2 to O2NNN(O)OH without and with catalyst X (X = H2O, (H2O)2, (H2O)3, HCOOH, H2SO4, CH3CH2COOH and HN(NO2)2) have been investigated theoretically at the CBS-QB3 level of theory. Our results show that the catalyst X (X = H2O, (H2O)2, (H2O)3, HCOOH, H2SO4 and CH3CH2COOH) shows different positive catalytic effects on reducing the apparent activation energy of the isomerisation reaction processes. Such different catalytic effects are mainly related to the number of hydrogen bonds and the size of the ring structure in X (X = H2O, (H2O)2 and (H2O)3)-assisted transition states, as well as different values of pKa for H2SO4, HCOOH and CH3CH2COOH. Very interesting is also the fact that H2SO4-assisted reaction is the most favourable for the hydrogen transfer from HN(NO2)2 to O2NNN(O)OH, due to the smallest pKa (?3.0) value of H2SO4 than H2O, HCOOH, H2SO4 and CH3CH2COOH, and also because of the largest ∠X???H???Y (the angle between the hydrogen bond donor and acceptor) involved in H2SO4-assisted transition state. Compared to the self-catalysis of the isomerisation mechanisms of HN(NO2)2 to O2NNN(O)OH, the apparent activation energy of H2SO4-assisted channel also reduces by 9.6 kcal?mol?1, indicating that H2SO4 can affect the isomerisation of HN(NO2)2 to O2NNN(O)OH, most obvious among all the catalysts H2O, (H2O)2, (H2O)3, HCOOH, H2SO4, CH3CH2COOH and HN(NO2)2.  相似文献   

20.
M?ssbauer spectroscopy, x-ray diffraction, and electrical resistance [R(P,T)] studies in Fe(OH)(2) to 40 GPa revealed an unforeseen process by which a gradual Fe2+ oxidation takes place, starting at approximately 8 GPa reaching 70% Fe3+ abundance at 40 GPa. The nonreversible process Fe2+-->Fe3++e(-) occurs with no structural transition. The "ejected" electrons form a deep band within the high-pressure electronic manifold becoming weakly localized at P>50 GPa. This process is attributed to an effective ionization potential created by the pressure induced orientationally deformed (OH) dipoles and the unusual small binding energy of the valence electron in Fe2+(OH)(2).  相似文献   

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