A photoionization study of the ion-neutral complexes CH3CH +CH 3 · CH2CH3] and CH3CH2CH+CH 3 · CH3 in the gas phase: Formation,H-transfer and C—C bond formation between partners,and channeling of energy into dissociation

Photoionization mass spectrometry was used to investigate the dynamics of ion-neutral complex-mediated dissociations of the n-pentane ion (1). Reinterpretation of previous data demonstrates that a fraction of ions 1 isomerizes to the 2-methylbutane ion (2) through the complex CH₃CH⁺CH ₃ ^· CH₂CH₃ (3), but not through CH₃CH⁺CH₂CH ₃ ^· CH₃ (4). The appearance energy for C₃Hin ₇ ⁺ formation from 1 is 66 kJ mol^?1 below that expected for the formation of n-C₃H ₇ ⁺ and just above that expected for formation of i-C₃H ₇ ⁺ . This demonstrates that the H shift that isomerizes C₃H ₇ ⁺ is synchronized with bond cleavage at the threshold for dissociation to that product. It is suggested that ions that contain n-alkyl chains generally dissociate directly to more stable rearranged carbenium ions. Ethane elimination from 3 is estimated to be about seven times more frequent than is C-C bond formation between the partners in that complex to form 2, which demonstrates a substantial preference in 3 for H abstraction over C-C bond formation. In 1 → CH₃CH⁺CH₂CH₃ + CH₃ by direct cleavage of the C1–C2 bond, the fragments part rapidly enough to prevent any reaction between them. However, 1 → 2 → 4 → C4H ₈ ⁺ + CH₄ occurs in this same energy range. Thus some of the potential energy made available by the isomerization of n-C₄H₉ in 1 is specifically channeled into the coordinate for dissociation. In contrast, analogous formation of 3 by 1 → 3 is predominantly followed by reaction between the electrostatically bound partners.     

Synthesis and Characterization of （CH3CH2CH2CH2NH3）2SnBr6

1 INTRODUCTION Recently, the researches on inorganic-organic hy-brid compounds represent an advanced field in mate-rial science[1]. At the molecular level, the combina-tion of two extremely different components providesan avenue to design new hybrid materials as well asthe ability to modulate properties of one or more ofthe components[2～6]. Some attractive properties, suchas efficient luminescence[2～4], ideal thermal and me-chanical stability, interesting magnetic[5], non-linearoptical[…     

Geometric shielding corrections for calculation of electron scattering by CO2, C2H2, CHCl3, CH2Cl2, CH3Cl,CHF3, CH2F2 and CH3F at 30–5000 eV

Taking into account the changes of the geometric shielding effect in a molecule as the incident electron energy varies, an empirical fraction, which depends on the energy of the incident electrons, the target's molecular dimension and the atomic and electronic numbers in the molecule, is presented. Using this empirical fraction, a new formulation of the additivity rule is proposed. Using the new additivity rule, the total cross sections of electron scattering by CO₂, C₂H₂, CHCl₃, CH₂Cl₂, CH₃Cl, CHF₃, CH₂F₂ and CH₃F are calculated at the Hartree–Fork level at 30–5000 eV. The quantitative total cross sections are compared with those obtained by experiments and other theories, and good agreement is obtained over a wide energy range, especially above 100 eV.     

Effects of excitation energy on the autodetachment lifetimes of small iodide-doped ROH clusters (R═H-, CH3-, CH3CH(2)-)

The effect of excitation energy on the lifetimes of the charge-transfer-to-solvent (CTTS) states of small (4 ≤ n ≤ 10) iodide-doped water and alcohol clusters was explored using femtosecond time-resolved photoelectron imaging. Excitation of the CTTS state at wavelengths ranging from 272 to 238 nm leads to the formation of the I···(ROH)(n)(-) (R═H-, CH(3)-, and CH(3)CH(2)-) species, which can be thought of as a vibrationally excited bare solvent cluster anion perturbed by an iodine atom. Autodetachment lifetimes for alcohol-containing clusters range from 1 to 71 ps, while water clusters survive for hundreds of ps in this size range. Autodetachment lifetimes were observed to decrease significantly with increasing excitation energy for a particular number and type of solvent molecules. The application of Klots' model for thermionic emission from clusters to I(-)(H(2)O)(5) and I(-)(CH(3)OH)(7) qualitatively reproduces experimental trends and reveals a high sensitivity to energy parametrization while remaining relatively insensitive to the number of vibrational modes. Experimental and computational results therefore suggest that the rate of electron emission is primarily determined by the energetics of the cluster system rather than by details of molecular structure.     

Theoretical Studies of the Reaction Mechanisms of CH3S＋NO2

The potential energy surface for the CH3S NO2 reaction has been studied using the ab initio G3(MP2) method. A variety of possible complexes and saddle points along the minimum energy reaction paths have been characterized at UMP2 (full)/6-31G(d) level. The calculations reveal dominating reaction mechanisms of the title reaction: CH3S NO2 firstly produce intermediate CH3SONO,then break up into CH3SO NO. The results are valuable to understand the atmospheric sulfur compounds oxidation mechanism.     

Ab initio study of the complexes of first-row transition-metal ions with CH, CH_2, and CH_3

The geometries and bonding characteristics of the complexes of the first-row transition-metal ions with CH, CH_2 and CH_3 were investigated by ab initio molecular orbital theory. MCH~ and MCH_2~ are linear and coplanar, re spectively. Both of them are with obvious treble or double bond characteristics, but these multiple bonds are mostly "im perfect". The calculated bond dissociation energies of C--M~ , C=M~ and C≡M~ are mostly close to the experi mental values, and appear in similar periodic trends from Sc to Zn.     

Impact of Water Molecules on the Isomerization of CH3S（OH）CH2 to CH3S（O）CH3： A Computational Investigation

The isomerization of CH3S（OH）CH2 to CH3S（O）CH3 in the absence and presence of water has been investigated at the G3XMP2//B3LYP/6-311 ＋ G（2df, p） level. The naked isomerization, the reaction without water, gives the high barrier height （21.56 kcal.mol^-1）. Three models are constructed to describe the water influence on the isomerization, that is, water molecules are the catalyst and the microsolvation, and water molecules act as the catalyst and microsolvation simultaneously. Our results show that the isomerization barrier heights of CH3S（OH）CH2 to CH3S（O）CH3 are reduced by 12.32, 11.04, and 7.80 kcal.mol^-1, respectively, when one, two, and three water molecules are performed as catalyst, in contrast to the naked isomerization. Moreover, the rate constants of the isomerization are calculated using the transition state theory with the Wigner tunneling correction over the temperature range of 240-425 K. We find that the rate constant of a single water molecule as the catalyst is 1.58 times larger than the naked isomerization at 325 K, whereas it is slower by 6 orders of magnitude when water molecule serves as the microsolvation at 325 K, compared to naked reaction. So the water-catalyzed isomerization of CH3S（OH）CH2 to CH3S（O）CH3 is predicted to be the key role in lowering the activation energy. The isomerization involving water molecules acting as mierosolvation is unfavorable under atmospheric conditions.     

反常蓝移单电子锂键Y…Li-CH3[Y=CH3, CH2CH3, CH(CH3)2, C(CH3)3]体系的结构与性质

在密度泛函理论B3LYP/6-311++G(d,p)及MP2/6-311++G(d,p)水平上研究了单电子锂键复合物Y…Li—CH3[Y=CH3, CH2CH3, CH(CH3)2, C(CH3)3]的结构与性质. 结果表明, 三种单电子锂键复合物H3CH2C…Li—CH3(II), (H3C)2HC…Li—CH3(III)和(H3C)3C…Li—CH3(IV)单电子锂键强度依II(-26.7 kJ·mol-1)相似文献   

Syntheses and Characterizations of （CH3CH2CH2CH2NH3）6（BiI6）（I）2I3 and （NH3CH2CH2NH3）2Bi2I10

The title compounds have been respectively synthesized by solution process and solvothermal reaction, and their crystal structures were determined by X-ray diffraction method. For （CH3CH2CH2CH2NH3）6（BiI6）（I）2I3 1, it crystallizes in tficlinic, space group P1^- with Mr = 2049.76, a = 8.5719（1）, b = 11.7461（3）, c = 15.700（1）A, V = 1451.4（1）A^3, Z = 1, Dc = 2.345 g/cm^3, F（000） = 924, μ（MoKα） = 8.907 mm^-1, T = 293（2） K, the final R = 0.0655 and wR = 0.0804 for 2399 observed reflections with I 〉 2σ（I）. For （NH3CH2CH2NH3）2Bi2I10 2, it crystallizes in monoclinic, space group P21/n with Mr= 1811.20, a = 8.434（4）, b = 13.862（6）, c = 13.362（6）A, V = 1499.9（12）A^3, Z = 2, Dc = 4.010 g/cm^3, F（000） = 1536,μ（MoKα） = 22.007 mm^-1, T = 293（2） K, the final R = 0.0584 and wR = 0.1451 for 1798 observed reflections with I 〉 2σ（I）. The structures of 1 and 2 contain halobismuthate monomer and dimers, respectively. It is noteworthy that the dimers and their organic counters in 2 connect each other by N…I hydrogen bonds to form a layered structure, and the electrostatic interactions and crystal packing forces between layers give rise to the packing of the crystal. The optical absorption spectra of 1 and 2 reveal the appearance of sharp optical gaps of 2.13 and 2.01 eV, respectively.     

Accurate ab initio potential energy surface, thermochemistry, and dynamics of the Cl(2P, 2P(3/2) + CH4 → HCl + CH3 and H + CH3Cl reactions

We report a high-quality, ab initio, full-dimensional global potential energy surface (PES) for the Cl((2)P, (2)P(3/2)) + CH(4) reaction, which describes both the abstraction (HCl + CH(3)) and substitution (H + CH(3)Cl) channels. The analytical PES is a least-squares fit, using a basis of permutationally invariant polynomials, to roughly 16,000 ab initio energy points, obtained by an efficient composite method, including counterpoise and spin-orbit corrections for the entrance channel. This composite method is shown to provide accuracy almost equal to all-electron CCSD(T)/aug-cc-pCVQZ results, but at much lower computational cost. Details of the PES, as well as additional high-level benchmark characterization of structures and energetics are reported. The PES has classical barrier heights of 2650 and 15,060 cm(-1) (relative to Cl((2)P(3/2)) + CH(4)(eq)), respectively, for the abstraction and substitution reactions, in good agreement with the corresponding new computed benchmark values, 2670 and 14,720 cm(-1). The PES also accurately describes the potential wells in the entrance and exit channels for the abstraction reaction. Quasiclassical trajectory calculations using the PES show that (a) the inclusion of the spin-orbit corrections in the PES decreases the cross sections by a factor of 1.5-2.5 at low collision energies (E(coll)); (b) at E(coll) ≈ 13,000 cm(-1) the substitution channel opens and the H/HCl ratio increases rapidly with E(coll); (c) the maximum impact parameter (b(max)) for the abstraction reaction is ~6 bohr; whereas b(max) is only ~2 bohr for the substitution; (d) the HCl and CH(3) products are mainly in the vibrational ground state even at very high E(coll); and (e) the HCl rotational distributions are cold, in excellent agreement with experiment at E(coll) = 1280 cm(-1).     

The Nature of Conformational Polymorphism in the Crystals of Ph3Sb(O2CCH2–CH=CH2)2

Russian Journal of Coordination Chemistry - Crystallization of the Ph3Sb(O2CCH2?CH=CH2)2 complex upon fast solvent (benzene) evaporation gives monoclinic crystals (I), whereas in the case of...     

Measurement of the rate constants for the reactions of the IO• radical with sulfur-containing compounds H2S, (CH3)2S, and SO2

The reactions of iodine monoxide (IO^•) with sulfur-containing compounds, which are important for the atmospheric chemistry, are studied. An attempt is made to distinguish between the heterogeneous and homogeneous reaction pathways. It is shown that, under the experimental conditions, the reactions proceed on the wall and generate iodine atoms into the gas phase. It is found that, at room temperature, the rate constants for the gas-phase reactions of IO^• with (CH₃)₂S and H₂S are lower than 2.5 × 10⁻¹⁴ and 8.0 × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹, respectively; the rate constant for the gas-phase reaction of iodine monoxide with SO₂ ≤ 5.6 × 10⁻¹⁵ cm³ molecule⁻¹ s⁻¹.     

Quasi-classical trajectory study of the dynamics of the Cl + CH4→ HCl + CH3 reaction

We present an on-the-fly classical trajectory study of the Cl + CH(4)→ HCl + CH(3) reaction using a specific reaction parameter (SRP) AM1 Hamiltonian that was previously optimized for the Cl + ethane reaction [S. J. Greaves et al., J. Phys Chem A, 2008, 112, 9387]. The SRP-AM1 Hamiltonian is shown to be a good model for the potential energy surface of the title reaction. Calculated differential cross sections, obtained from trajectories propagated with the SRP-AM1 Hamiltonian compare favourably with experimental results for this system. Analysis of the vibrational modes of the methyl radical shows different scattering distributions for ground and vibrationally excited products.     

Crossed-beams studies of the dynamics of the H-atom abstraction reaction, O(3P) + CH4 → OH + CH3, at hyperthermal collision energies

The H-atom abstraction reaction, O((3)P) + CH(4) → OH + CH(3), has been studied at a hyperthermal collision energy of 64 kcal mol(-1) by two crossed-molecular-beams techniques. The OH products were detected with a rotatable mass spectrometer employing electron-impact ionization, and the CH(3) products were detected with the combination of resonance-enhanced multiphoton ionization (REMPI) and time-sliced ion velocity-map imaging. The OH products are mainly formed through a stripping mechanism, in which the reagent O atom approaches the CH(4) molecule at large impact parameters and the OH product is scattered in the forward direction: roughly the same direction as the reagent O atoms. Most of the available energy is partitioned into product translation. The dominance of the stripping mechanism is a unique feature of such H-atom abstraction reactions at hyperthermal collision energies. In the hyperthermal reaction of O((3)P) with CH(4), the H-atom abstraction reaction pathway accounts for 70% of the reactive collisions, while the H-atom elimination pathway to produce OCH(3) + H accounts for the other 30%.     

Intramolecular Rearrangements of >Si(O–C·=O)(CH2–CH3) and >Si(CH2–CH·–CH3)(CH2–CH3) Radicals

Using ESR and IR spectroscopy, the structures of >Si(O–C^·=O)(CH₂–CH₃) (1) and >Si(CH₂–CH^·–CH₃)(CH₂–CH₃) (2) radicals were deciphered. The directions and kinetic parameters of reactions of intramolecular rearrangements in these radicals were determined. The reactions of hydrogen atom abstraction in radical (1) from the CH₂ and CH₃ groups were studied. It was found that the endothermic reaction of hydrogen atom abstraction from the methyl group occurs at a higher rate than the exothermic reaction with the methylene group. The differences are determined by changes in the size of a cyclic transition state. Based on the experimental data, the strengths of separate C–H bonds in surface fragments are compared. The rearrangement >Si(CH₂–CH^·–CH₃)(CH₂–CH₃) >Si(C^·(CH₃)₂)(CH₂–CH₃) was discovered and its mechanism was determined. One of its steps is the skeletal isomerization Si- (2)- _. (1)Si- (1)- _. (2). Experimental data are analyzed using the results of quantum-chemical calculations of model systems.     

Ab initio study of Eu3+–L (L=H2O,H2S,NH2CH3, S(CH3)2, imidazole) complexes

The ground states and binding energies of Eu³⁺–L (L=H₂O,H₂S,NH₂CH₃,S(CH₃)₂, imidazole) complexes has been determined using ab initio techniques. The binding is mostly electrostatic as expected. The empty f orbital is different for the S compounds, being a π-like orbital, while for the O and N containing ligands it is a σ-like orbital. However, the range in the binding energies for the different f holes is small.     

Solvent dependence of peak frequencies and bandwidths of the ν4 vibration of the series CH3MCl3, M  C,Si, Ge,Sn

The Raman spectra of the carbon—chlorine symmetric stretching mode, ν₄, of the Group IVA methylmetal trichlorides (CH₃MCl₃, M  C, Si, Ge, Sn) were acquired in a number of solvents of varying molecular properties. Non-linear curve fitting procedures were used to separate the four band components resulting from chlorine isotope splitting.The band maxima of the two lighter members of the series were observed to shift to lower frequency with increasing solvent polarizability, indicating the predominance of solute—solvent dispersion forces. In the germanium and tin compounds, on the other hand, the peak frequencies were correlated, instead, with solvent dipole moment. This result is in contrast to earlier studies on the ν₁ (CH₃ symmetric stretching) vibration, for which dispersion interactions are the dominant frequency displacement mechanism in all four compounds.The bandwidths of the ν₄ vibration were found to depend on dipolar interactions in the germanium and tin compounds. However, this correlation was not observed for the two lighter series members, nor for the carbon—chlorine antisymmetric stretching vibration in CH₃SnCl₃.