Mechanistic and kinetic study of CF3CH═CH2 + OH reaction

The potential energy surfaces of the CF(3)CH═CH(2) + OH reaction have been investigated at the BMC-CCSD level based on the geometric parameters optimized at the MP2/6-311++G(d,p) level. Various possible H (or F)-abstraction and addition/elimination pathways are considered. Temperature- and pressure-dependent rate constants have been determined using Rice-Ramsperger-Kassel-Marcus theory with tunneling correction. It is shown that IM1 (CF(3)CHCH(2)OH) and IM2 (CF(3)CHOHCH(2)) formed by collisional stabilization are major products at 100 Torr pressure of Ar and in the temperature range of T < 700 K (at P = 700 Torr with N(2) as bath gas, T ≤ 900 K), whereas CH(2)═CHOH and CF(3) produced by the addition/elimination pathway are the dominant end products at 700-2000 K. The production of CF(3)CHCH and CF(3)CCH(2) produced by hydrogen abstractions become important at T ≥ 2000 K. The calculated results are in good agreement with available experimental data. The present theoretical study is helpful for the understanding the characteristics of the reaction of CF(3)CH═CH(2) + OH.     

Unimolecular reactions in the CF3CH2Cl ↔ CF2ClCH2F system: isomerization by interchange of Cl and F atoms

The recombination of CF(2)Cl and CH(2)F radicals was used to prepare CF(2)ClCH(2)F* molecules with 93 ± 2 kcal mol(-1) of vibrational energy in a room temperature bath gas. The observed unimolecular reactions in order of relative importance were: (1) 1,2-ClH elimination to give CF(2)═CHF, (2) isomerization to CF(3)CH(2)Cl by the interchange of F and Cl atoms and (3) 1,2-FH elimination to give E- and Z-CFCl═CHF. Since the isomerization reaction is 12 kcal mol(-1) exothermic, the CF(3)CH(2)Cl* molecules have 105 kcal mol(-1) of internal energy and they can eliminate HF to give CF(2)═CHCl, decompose by rupture of the C-Cl bond, or isomerize back to CF(2)ClCH(2)F. These data, which provide experimental rate constants, are combined with previously published results for chemically activated CF(3)CH(2)Cl* formed by the recombination of CF(3) and CH(2)Cl radicals to provide a comprehensive view of the CF(3)CH(2)Cl* ? CF(2)ClCH(2)F* unimolecular reaction system. The experimental rate constants are matched to calculated statistical rate constants to assign threshold energies for the observed reactions. The models for the molecules and transition states needed for the rate constant calculations were obtained from electronic structures calculated from density functional theory. The previously proposed explanation for the formation of CF(2)═CHF in thermal and infrared multiphoton excitation studies of CF(3)CH(2)Cl, which was 2,2-HCl elimination from CF(3)CH(2)Cl followed by migration of the F atom in CF(3)CH, should be replaced by the Cl/F interchange reaction followed by a conventional 1,2-ClH elimination from CF(2)ClCH(2)F. The unimolecular reactions are augmented by free-radical chemistry initiated by reactions of Cl and F atoms in the thermal decomposition of CF(3)CH(2)Cl and CF(2)ClCH(2)F.     

Mechanisms and Kinetics of Reactions of the O（^1D,^3P） ＋ CF3Cl System

In the stratosphere,CF3Cl(CFC13)can either photodecompose or react directly with atomic oxygen to generate ozone-depleting agents such as Cl and ClO in the gas phase[1—3].Since the1970s,attention has been focused on the effects of these compounds on the …     

Pulse radiolysis study of energy transfer processes in Xe–M mixtures (M=CH2F2,CHF3,CHF2Cl,CHFCl2 and CF3Cl)

The time-resolved spectroscopy measurements were used to study the kinetics of energy transfer process in the pulse radiolysis of xenon- fluoro- and chlorofluoromethanes mixtures. The main channel, at xenon pressure above 40 Torr, seems to be of third order, while at lower xenon pressures the second order process was the main one.     

Structure of carbon fluorochlorides CF n Cl m (n,m ≤ 3) and their singly charged negative ions

The electronic and geometrical structures of carbon fluorochlorides with low coordination numbers (n 3) and their singly charged anions are calculated using the functional density method. The results of the calculations are used to evaluate the electron affinities (EA) of the neutral compounds and the first ionization potentials of the anions as well as the energies of fragmentation through different decay channels of both series. The adiabatic EA of carbon fluorochloride CF _k Cl _3–k is shown to be determined mainly by the presence of a CX₂ unit in these compounds. There are no monotonic changes in stability of either the neutral compounds withn = 3 or the anions withn = 2 or 3 upon successive substitution of one halogen by another.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1044–1049, June, 1993.     

HO^3^5Cl,HO^3^7Cl,DO^3^5Cl和DO^3^7Cl的振动激发态光谱研究

本文用自洽场组态相互作用方法(SCF-CI)精确计算了次氯酸分子HOCl的振动激发态的能级以及次氯酸分子中的H和Cl分别被D和^3^7Cl取代后的HO^3^7Cl,DO^3^5Cl和DO^3^7Cl的同位素效应, 这些理论计算值与已有的实验结果吻合较好, 还预测了一些尚未观测到的谱线频率及同位素效应。     

CH3OCF2CF2OCH3+Cl的反应机理及动力学性质

利用密度泛函理论直接动力学方法研究了反应CH₃OCF₂CF₂OCH₃+Cl的微观机理和动力学性质. 在BB1K/6-31+G(d,p)水平上获得了反应的势能面信息, 计算中考虑了反应物CH₃OCF₂CF₂OCH₃两个稳定构象(SC1和SC2)的氢提取通道和取代反应通道. 利用改进的正则变分过渡态理论结合小曲率隧道效应(ICVT/SCT)计算了各氢提取通道的速率常数, 进而根据Boltzmann配分函数得到总包反应速率常数(k_T)以及每个构象对总反应的贡献. 结果表明296 K温度下计算的k_T(ICVT/SCT)值与已有实验值符合得很好. 由于缺乏其他温度速率常数的实验数据, 我们预测了该反应在200-2000 K温度区间内反应速率常数的三参数表达式: k_T=0.40×10^-14T^1.05exp(-206.16/T).     

用直接动力学方法确定CF3CHFCF3与Cl原子反应的速率常数

采用直接动力学方法研究了CF3CHFCF3与氯原子反应的动力学特性,利用包含小曲率隧道效应的正则变分过渡态理论确定了200～2 000 K温度区间内反应的速率常数.     

The Cl−NH3, Cl−H2O,F−NH3 and F−H2O clusters and their photoelectron spectra

The geometries of the Cl^–NH₃, Cl^–H₂O, F^–NH₃ and F^–H₂O clusters are optimized using the coupled cluster method. The four lowest ionization potentials are then calculated, leading to the ground and low excited states of the neutral species. The first three IPs describe ionization from the externalp state of the halogen atom, whereas the fourth corresponds to ionization from the NH₃ or H₂O moiety, leading to charge transfer complexes. These complexes were recently observed in the photoelectron spectrum of Cl^–NH₃, in full accord with our calculations.Supported in part by the U.S.-Israel Binational Science Foundation     

Li,K∥F,NO3 and Li,K∥Cl,NO3 three-component reciprocal systems

Phase equilibria in Li,K∥F,NO₃ and Li,K∥Cl,NO₃ three-component reciprocal systems were studied by differential scanning calorimetry (DSC). Eutectic compositions (mol %) in the Li,K∥F,NO₃ system were determined to be as follows: 5.0 LiF, 10.0 KF, and 85.0 KNO₃ with T _m = 281°C and 48.5 KNO₃, 44.0 LiNO₃, and 7.5 LiF with T _m = 105°C. Eutectic compositions (mol %) in the Li,K∥Cl,NO₃ system were determined to be as follows: 10.0 LiCl, 32.1 KCl, and 57.9 LiNO₃ with T _m = 147°C and 44.5 KNO₃, 45.0 LiNO₃, and 10.5 KCl with T _m = 97°C.     

On the Cl···N halogen bond: a rotational study of CF3Cl···NH3

The rotational spectra of six isotopologues (CF(3)(35)Cl···(14)NH(3), CF(3)(37)Cl···(14)NH(3), CF(3)(35)Cl···(15)NH(3), CF(3)(37)Cl···(15)NH(3), CF(3)(35)Cl···(14)ND(3) and CF(3)(37)Cl···(14)ND(3)) of the CF(3)Cl···NH(3) adduct have been investigated and analyzed by pulsed jet Fourier transform microwave spectroscopy. Rotational, centrifugal distortion and quadrupole ((35)Cl, (37)Cl, (14)N) coupling constants have been precisely obtained. The two subunits of the complex are held together via a Cl···N halogen bond interaction. Information on the internal dynamics and on the dissociation energy of the complex is provided.     

Chlorination of charged buckyballs: reactions of C60x+ cations (x = 1–3) with Cl2, CCl4, CDCl3, CH2Cl2, and CH3Cl

The chlorination of singly and multiply charged C₆₀ cations has been investigated with the selected-ion flow tube technique. Observations are reported for the reactions of C₆₀^·+, C₆₀²⁺ and C₆₀^·3+ with Cl₂, CCl₄, CDCl₃, CH₂Cl₂ and CH₃Cl at room temperature (295 ± 2 K) in helium at a total pressure of 0.35 ± 0.02 Torr. C₆₀^·+ and C₆₀²⁺ were observed not to chlorinate, or react in any other way, with these five molecules. Chlorine also did not react with C₆₀^·3+, but bimolecular chloride transfer and electron transfer reactions, reactions that result in charge reduction/charge separation, were observed to occur with CCl₄, CDCl₃, CH₂Cl₂ and CH₃Cl. Chloride transfer was the predominant channel seen with CCl₄, CDCl₃ and CH₂Cl₂ while electron transfer dominates the reaction with CH₃Cl. These results are consistent with trends in chloride affinity and ionization energy. The reluctant chlorination of the first two charge states of C₆₀ is attributed to the energy required to distort the carbon cage upon bond formation, while the observed chloride transfer to C₆₀^·3+ is attributed to the greater electrostatic interactions with this ion.     

Bond distances and bond angles of the C10 skeleton in naphthalene derivatives as hard bond parameters:35Cl NQR and structure of 1,8-diaminonaphthalene · Cl2HCCOOH, 1,8-diaminonaphthalene · Cl3CCOOH, 1-aminonaphthalene · Cl3CCOOH,and 1,8-diaminonaphthalene

The structures of several naphthalene derivatives and their³⁵Cl NQR spectra have been investigated. 1,8-Diaminonaphthalene,C _2v ⁹ -Pna2 ₁, Z = 8,a (in pm) = 881,b = 1577,c = 1213; 1,8-diaminonaphthalene monodichloroacetate,C _2h ⁶ -C2/c, Z = 8,a = 2050,b = 584,c = 2333, (in degrees) = 110.1; 1,8-diaminonaphthalene monotrichloroacetate,C ₁ ¹ -P¯1, Z=2,a=1211,b=1062,c=589,=74.8,=80.1,=70.9; 1-aminonaphthalene trichloroacetate,D _2h ¹⁵ -Pbca, Z=8,a=2347,b=1289,c=889. The³⁵Cl NQR spectrum of 1,8-diaminonaphthalene monodichloroacetate is a doublet, the frequencies decreasing with increasing temperature from 77 to 217 K at which temperatureT _b the NQR signals bleach out. A³⁵Cl NQR triplet is found for 1,8-diaminonaphthalene monotrichloracetate in the range 77 77K 207 (=T _b ). 1-Amino-naphthalene trichloroacetate shows a³⁵Cl NQR triplet, too, withT _b = 136 K. Characteristic for the intermolecular interactions are hydrogen bonds in the chloroacetic acid salts; each NH₃ group forms three hydrogen bonds, and of the two oxygens one is involved in two such bonds, one in one bond. Thereby units of two cations and two anions are formed, and these dirners are connected to strings by hydrogen bonds. Additional van der Waals interactions between the chlorine atoms and the naphthalene ring system are observed. Comparison of the intramolecular bond distances C(i)-C(j) of the C₁₀ naphthalene skeleton for 41 naphthalene derivatives (present data and literature) shows that the bond distances C(i)-C(j)are little influenced by substitution, as is the mean bond length. Shorter and longer distances prove a partial localization of charge at C(1)-C(2), C(3)-C(4), C(5)-C(6), and C(7)-C(8). Regularities within the bond angles and characteristic influences of 1,8-disubstitution on it are discussed.     

Synthesis, microwave spectrum, and dipole moment of allenylisocyanide (H2C═C═CHNC), a compound of potential astrochemical interest

An improved synthesis of a compound of potential astrochemical interest, allenylisocyanide (H(2)C═C═CHNC), is reported together with its microwave spectrum, which has been investigated in the 8-120 GHz spectral range to facilitate a potential identification in interstellar space. The spectra of the ground vibrational state and of five vibrationally excited states belonging to three different vibrational modes have been assigned for the parent species. A total of 658 transitions with a maximum value of J = 71 were assigned for the ground state and accurate values obtained for the rotational and quartic centrifugal distortion constants. The spectra of five heavy-atom ((13)C and (15)N) isotopologues were also assigned. The dipole moment was determined to be μ(a) = 11.93(16) × 10(-30) C m, μ(b) = 4.393(44) × 10(-30) C m, and μ(tot) = 12.71(16) × 10(-30) C m. The spectroscopic work has been augmented by theoretical calculations at the CCSD/cc-pVTZ and B3LYP/cc-pVTZ levels of theory. The theoretical calculations are generally in good agreement with the experimental results.     

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.     

Synthesis of a uranium(VI)-carbene: reductive formation of uranyl(V)-methanides, oxidative preparation of a [R2C═U═O]2+ analogue of the [O═U═O]2+ uranyl ion (R = Ph2PNSiMe3), and comparison of the nature of U(IV)═C, U(V)═C, and U(VI)═C double bonds

We report attempts to prepare uranyl(VI)- and uranium(VI) carbenes utilizing deprotonation and oxidation strategies. Treatment of the uranyl(VI)-methanide complex [(BIPMH)UO(2)Cl(THF)] [1, BIPMH = HC(PPh(2)NSiMe(3))(2)] with benzyl-sodium did not afford a uranyl(VI)-carbene via deprotonation. Instead, one-electron reduction and isolation of di- and trinuclear [UO(2)(BIPMH)(μ-Cl)UO(μ-O){BIPMH}] (2) and [UO(μ-O)(BIPMH)(μ(3)-Cl){UO(μ-O)(BIPMH)}(2)] (3), respectively, with concomitant elimination of dibenzyl, was observed. Complexes 2 and 3 represent the first examples of organometallic uranyl(V), and 3 is notable for exhibiting rare cation-cation interactions between uranyl(VI) and uranyl(V) groups. In contrast, two-electron oxidation of the uranium(IV)-carbene [(BIPM)UCl(3)Li(THF)(2)] (4) by 4-morpholine N-oxide afforded the first uranium(VI)-carbene [(BIPM)UOCl(2)] (6). Complex 6 exhibits a trans-CUO linkage that represents a [R(2)C═U═O](2+) analogue of the uranyl ion. Notably, treatment of 4 with other oxidants such as Me(3)NO, C(5)H(5)NO, and TEMPO afforded 1 as the only isolable product. Computational studies of 4, the uranium(V)-carbene [(BIPM)UCl(2)I] (5), and 6 reveal polarized covalent U═C double bonds in each case whose nature is significantly affected by the oxidation state of uranium. Natural Bond Order analyses indicate that upon oxidation from uranium(IV) to (V) to (VI) the uranium contribution to the U═C σ-bond can increase from ca. 18 to 32% and within this component the orbital composition is dominated by 5f character. For the corresponding U═C π-components, the uranium contribution increases from ca. 18 to 26% but then decreases to ca. 24% and is again dominated by 5f contributions. The calculations suggest that as a function of increasing oxidation state of uranium the radial contraction of the valence 5f and 6d orbitals of uranium may outweigh the increased polarizing power of uranium in 6 compared to 5.     

Rules on intrapair and interpair correlation energy for Cl, Cl−and MCl (M=H, Li, Na, K)

According to the calculation results of the intrapair and interpair correlation energy for the title systems, it has been found that the intrapair correlation energy of K shell of Cl is almost a constant and both the intrashell and intershell correlation energy of K and L shell changes little. It has also been found that in MCl series compounds the value of Cl correlation energy contribution depends on the ionicity of MCl compounds, i.e., the Cl correlation energy contribution increases with the increase of the ionic bond strength of the compound and this value is always less than the correlation energy of Cl^- anion but always larger than that of Cl atom. These rules are helpful for the estimation of the correlation energy of ionic compounds and the energy changes of chemical reactions.     

Bis-trifluoromethyl Effect: Doubled Transitions in the Rotational Spectra of Hexafluoroisobutene, (CF(3))(2)C═CH(2)

Rotational spectra for hexafluoroisobutene, and its (13)C isotopologues, have been recorded between 8 and 16 GHz using a chirped pulse, Fourier transform microwave spectrometer. Notably, all spectra observed are doubled with separations between the doublets being between 1 and 60 MHz. We propose that the bis-trifluoromethyl groups of the target molecule are staggered in the equilibrium configuration, and that a novel, out-of-phase rotation through a F-CCC-F planar configuration with low barrier (<100 cm(-1)), leads to the observed doubled rotational spectra.     

连续二氧化碳激光敏化氧化CF2HCL,CF2=CF2,CF2=CFCl,CHCl3,CHCl=CCl2和CH2=CH2

本文报道了连续二氧化碳激光敏化氧化CF_2HCl,CF_2==CF_2,CF_2==CFCL,CHCl_3,CHCl==CCl_2和CH_2==CH_2的反应,讨论了某些反应的机制。结果表明,激光敏化方法可以使不能直接吸收激光的反应物分子在气相中发生反应,并有可能产生卡宾。