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1.
Twenty-two isomers/conformers of C3H6S+√ radical cations have been identified and their heats of formation (ΔHf) at 0 and 298 K have been calculated using the Gaussian-3 (G3) method. Seven of these isomers are known and their ΔHf data are available in the literature for comparison. The least energy isomer is found to be the thioacetone radical cation (4+) with C2v symmetry. In contrast, the least energy C3H6O+√ isomer is the 1-propen-2-ol radical cation. The G3 ΔHf298 of 4+ is calculated to be 859.4 kJ mol−1, ca. 38 kJ mol−1 higher than the literature value, ≤821 kJ mol−1. For allyl mercaptan radical cation (7+), the G3 ΔHf298 is calculated to be 927.8 kJ mol−1, also not in good agreement with the experimental estimate, 956 kJ mol−1. Upon examining the experimental data and carrying out further calculations, it is shown that the G3 ΔHf298 values for 4+ and 7+ should be more reliable than the compiled values. For the five remaining cations with available experimental thermal data, the agreement between the experimental and G3 results ranges from fair to excellent.

Cation CH3CHSCH2+√ (10+) has the least energy among the eleven distonic radical cations identified. Their ΔHf298 values range from 918 to 1151 kJ mol−1. Nevertheless, only one of them, CH2=SCH2CH2+√ (12+), has been observed. Its G3 ΔHf298 value is 980.9 kJ mol−1, in fair agreement with the experimental result, 990 kJ mol−1.

A couple of reactions involving C3H6S+√ isomers CH2=SCH2CH2+√ (12+) and trimethylene sulfide radical cation (13+) have also been studied with the G3 method and the results are consistent with experimental findings.  相似文献   


2.
Ab initio (HF/6-31G** and B3LYP/6-31 + + G**) methods have been used to study the stability and structure of complexes between CH3SO3 and CH3NH+3 or C(NH2)+3. Results show that no hydrogen jump is involved in the complex formations, which is different from previous work studying complexes between CH3COO and CH3NH+3. In addition, we have studied complexes between CH3SO3 and HC(NH2)+3 or +H3NC(NH2)3, all of which have a cage structure.  相似文献   

3.
Oxidative alkylation of Cp*2TiX (Cp*: η5-C5Me5; X = OMe, Cl, N=C(H)tBu) and Cp*2TiMe by CdMe2 or ZnMe2 gives diamagnetic Cp*2Ti(Me)X and Cp*2TiMe2 respectively, and cadmium or zinc. The reactions of Cp*2TiR (R = Et, CH=CH2, Ph) with MMe2 (M = Cd, Zn) give statistical mixtures of Cp*2Ti(Me)R, Cp*2TiMe2 and Cp*2TiR2. Dimethylmercury does not react with Cp*2TiX.  相似文献   

4.
The geometries of HOOH, CH3OOH, and CH3OOCH3, were optimized with different basis sets (3-21G, 6-31G*(*) and D95**) at different levels of theory (HF, MP2, MP4, and CI). HF/3-21G optimizations result in planar trans conformations for all three peroxides. HF/6-31G** calculations predict skew conformations for HOOH and CH3OOH, but a planar trans struture for CH3OOCH3. For the larger basis set the calculated bond lengths, especially the O-O bonds, are too short. Optimizations for HOOH including electron correlation at the MP2, MP3, MP4, CI, and CCD level improve the agreement for bond lengths and the OOH angle, but result in dihedral angles Which are too large by 3– 8°. In the case of CH3OOCH3, similar calculations at the MP2 and CI level predict planar trans structures instead of the experimentally observed skew conformation. On the other hand, MP4 single point calculations at MP2 optimized parameters result in a correct skew structure. For all three peroxides a computationally “economic” method, i.e., single point calculations at MP2 or MP4 level with HF/3-21G optimized parameters, result in close agreement between calculated and experimental structures.  相似文献   

5.
Gaussian-2 ab initio calculations were performed to examine the six modes of unimolecular dissociation of cis-CH3CHSH+ (1+), trans-CH3CHSH+ (2+), and CH3SCH2+ (3+): 1+→CH3++trans-HCSH (1); 1+→CH3+trans-HCSH+ (2); 1+→CH4+HCS+ (3); 1+→H2+c-CH2CHS+ (4); 2+→H2+CH3CS+ (5); and 3+→H2+c-CH2CHS+ (6). Reactions (1) and (2) have endothermicities of 584 and 496 kJ mol−1, respectively. Loss of CH4 from 1+ (reaction (3)) proceeds through proton transfer from the S atom to the methyl group, followed by cleavage of the C–C bond. The reaction pathway has an energy barrier of 292 kJ mol−1 and a transition state with a wide spectrum of nonclassical structures. Reaction (4) has a critical energy of 296 kJ mol−1 and it also proceeds through the same proton transfer step as reaction (3), followed by elimination of H2. Formation of CH3CS+ from 2+ (reaction (5)) by loss of H2 proceeds through protonation of the methine (CH) group, followed by dissociation of the H2 moiety. Its energy barrier is 276 kJ mol−1. On both the MP2/6-31G* and QCISD/6-31G* potential-energy surfaces, the H2 1,1-elimination from 3+ (reaction (6)) proceeds via a nonclassical intermediate resembling c-CH3SCH2+ and has a critical energy of 269 kJ mol−1.  相似文献   

6.
Collisionally activated dissociation and neutralization-reionization experiments reveal that protonation of ethanol leads to two distinct isomers, the classical ion CH3CH2OH+2 and the proton-bound complex C2H4…H+…OH2. The neutral counterpart of the latter is unstable, whereas that of the former can be produced in a bound state if the CH3CH2OH+2 precursor ion is formed under low ion source pressure conditions and, thus, with higher internal energies. This suggests that there are substantial differences in the geometries of CH3CH2OH+2 and the hypervalent CH3CH2OH2 ·. This provides only a partial explanation for unusual isotope effects; C2H5OD2 ·, CH3CD2OD2 ·, and CD3CH2OD2 · are substantially more stable than C2D5OD2 · and C2H5OH2 ·.  相似文献   

7.
The activation barrier for the CH4 + H → CH3 + H2 reaction was evaluated with traditional ab initio and Density Functional Theory (DFT) methods. None of the applied ab initio and DFT methods was able to reproduce the experimental activation barrier of 11.0-12.0 kcal/mol. All ab initio methods (HF, MP2, MP3, MP4, QCISD, QCISD(T), G1, G2, and G2MP2) overestimated the activation energy. The best results were obtained with the G2 and G2MP2 ab initio computational approaches. The zero-point corrected energy was 14.4 kcal mol−1. Some of the exchange DFT methods (HFB) computed energies which were similar to the highly accurate ab initio methods, while the B3LYP hybrid DFT methods underestimated the activation barrier by 3 kcal mol−1. Gradient-corrected DFT methods underestimated the barrier even more. The gradient-corrected DFT method that incorporated the PW91 correlational functional even generated a negative reaction barrier. The suitability of some computational methods for accurately predicting the potential energy surface for this hydrogen radical abstraction reaction was discussed.  相似文献   

8.
Density functional calculations for hydrazoic acid HN3 and methyl azide CH3N3 and for the respective singly ionized structures HN+3 and CH3N+3 are reported. An analysis of the electrostatic solvent effects, based on the self-consistent reaction field approach, on the molecular properties and conformational equilibrium of CH3N3 is also reported. The results are sensitive to the basis set quality and show some dependence on the different representations for the exchange-correlation functions. For HN3 very good agreement with experiment is observed for several properties, such as the geometry, dipole moment, vibrational frequencies and for the adiabatic first ionization energy. For CH3N3 the energy difference between eclipsed (ec) and staggered (st) conformers (δec-st) is 2.5 kJ mol−1, in good agreement with the experimental value (2.9 kJ mol−1). However, for CH3N+3, δec-st is −3.2 kJ mol, reflecting a significant modification of the methyl group rotational potential after ionization. Solvent effects on the molecular properties of CH3N3 are important when it is solvated in a polar medium. The most significant modifications concern the dipole moment and the frequencies related to the CH3 symmetric stretch and torsion vibrational modes.  相似文献   

9.
Dimethyl diselenide is demonstrated to be among the most powerful reagents used to identify distonic radical cations. Most such ions readily abstract CH3Se. from dimethyl diselenide. The reaction is faster and more exclusive than CH3S. abstraction from dimethyl disulfide, a reaction used successfully in the past to identify numerous distonic ions. Very acidic distonic ions, such as HC+(OH)OCH.2, do not undergo CH3Se. abstraction, but instead protonate dimethyl diselenide. In sharp contrast to the reactivity of distonic ions, most conventional radical cations were found either to react by exclusive electron transfer or to be unreactive toward dimethyl diselenide. Hence, this reagent allows distinction of distonic and conventional isomers, which was demonstrated directly by examining two such isomer pairs. To be able to predict whether electron transfer is exothermic (and hence likely to occur), the ionization energy of dimethyl diselenide was determined by bracketing experiments. The low value obtained (7.9 ± 0.1 eV) indicates that dimethyl diselenide will react with many conventional carbon-, sulfur-, and oxygen-containing radical cations by electron transfer. Nitrogen-containing conventional radical cations were found either to react with dimethyl diselenide by electron transfer or to be unreactive.  相似文献   

10.
The transition 4A22E of Co2+ has been investigated in [N(CH3)4]2CoCl4 using optical absorption and magnetic circular dichroism. Three groups of lines with 274 cm−1 progressions were observed. The structure of the spectra indicates a J-T interaction in the 2E state with strong depression of the frequency of the J-T active mode. The ground-state splitting is 7.2 cm−1.  相似文献   

11.
The gaseous equilibria involving the molecules AuSi, AuSi2 and Au2Si have been studied by means of the Knudsen effusion technique combined with mass spectrometric analysis of the vapor. The experimentally determined reaction enthalpies were combined with appropriate literature data to obtain the following atomization energies (in kJ mole−1): D00[AuSi(g)] = 301.0 ± 6.0, D00[Au2Si(g)] = 582.7 ± 15 and D00[AuSi2(g)] = 602.1 ± 15. The corresponding D0298 values are: 305.2 ± 6.0, 589.1 ± 15 and 610.5 ± 15, and the standard heats of formation, ΔH0f,298, 518.6, 602.9 and 668.9, respectively.

Comparison of the atomization energies of these silicon—gold molecules with the literature values for the corresponding germanium—gold and tin—gold molecules indicates similarity in the nature of bonding.  相似文献   


12.
On the basis of ab initio MP2/6–31 + + G(2d,2p) calculations, we examined the potential energy surfaces of the water·hydrocarbon complexes H2O·CH4, H2O·C2H2 and H2O·C2H2 to locate all the minimum energy structures and estimate the hydrogen bond energies and vibrational frequencies associated with the C(spn)---H·O and the O---H·C(spn) bonds (n = 1−3). Our calculations show that H2O·C2H2, H2O·C2H4 and H2O·CH4 have two minimum energy structures (i.e., the C---H·O and O---H·C hydrogen bond forms), but H2O·C2H4 has only one when the vibrational motion is taken into account, the O---H·C hydrogen bond form. We have also computed the barrier for the interconversion from one minimum to the other. The fully optimized geometries of H2O·CH4, H2O·C2H4 and H2O·C2H2 as well as the vibrational shifts of the C---H stretching frequencies in their C---H·O hydrogen-bonded forms are in good agreement with the available experimental data. The calculated hydrogen bond energies show that the C(spn---H·O bond strengths decrease in the order C(sp)---H·O>C(sp2)---H·O>C(sp3)---O>C(sp3---H·O, which is also consistent with the available experimental data.  相似文献   

13.
The title complex [NH_3CH_2CH(NH_2)CH_3]_2 [M(Ⅵ)O_2(OC_6H_4O)_2](M= Mo_(0.6)W_(0.4))was synthesized via a simple solution-phase chemical route.The determination of single crystal X-ray diffraction revealed that the title compound is crystallized in a monoclinic system with P2(1)/n space group,a=1.0913(10)nm,b=1.0442(10)nm,c=1.8842(19)nm,α=90°,β=96.530(17)°,γ=90°,Z=4,and V=2.133(4)nm3.The mononuclear anionic unit [M(Ⅵ)O2(OC6H4O)2]2-displays chiral pseudo-octahedral [MO_6] coordination geometry and is linked by chiral cations via hydrogen bond and π…π stacking interaction.The transmission electron microscopy images show that the title complex is comprised of nano-particles with diameters ranging from 20 to 50 nm.The NMR study shows the 1H downfield chemical shifts of [NH_3CHaHbCH(NH_2)CH_3] cations in the title complex when it is mixed with adenosine-triphosphate(ATP),and the chemical shift difference between Ha and Hb is increased greatly,and most of the catecholate ligands dissociate from the central metal atoms.The DNA cleavage activity experiment reveals that DNA cleavage promoted by the title complex is lower than that by Na_2MoO_4 which possesses antitumor pro-perty,but higher than that by Na_2WO_4.  相似文献   

14.
The X-ray diffraction study of crystals isolated from solutions obtained by reaction of Ba(OMe)2 with Ti(OMe)4 (molar ratio 1:2) in methyl alcohol was carried out; the crystals of the methanol solvate of the double barium-titanium methoxide, [Ba2Ti4O(OMe)18(MeOH)7]·MeOH (1), contain two Ba2+ cations with different environments and two kinds of anionic binuclear titanium complexes with and without oxo-ligand, and thus can be formulated as [Ba(MeOH)2]2+[Ba(MeOH)5]2+[Ti2O(OMe)8]2−[Ti2(OMe)10]2−·MeOH.  相似文献   

15.
The infrared spectra of solid samples of C4H7K and C4D7K have been investigated in the 4000 to 30 cm−1 range. A complete assignment of intramolecular fundamentals of C4H7 and C4D7 ions and of potassium-allyl vibrations is proposed and the intramolecular force constants are calculated. The C(CH2)32− anion has been identified spectroscopically. Structures of C3H5, C4H7 and C(CH3)32− are discussed and compared with those optimised by the MINDO/3 method.  相似文献   

16.
Reduction of (C5H5)2TiCl2 with Zn in presence of benzyl cyanide gives the (μ-alkyl-ideneamido)titanocene complex [(C5H5)2TiCl]2[μ-{N=C(CH2C6H5)---C(CH2C6H5)=N}] with C---C bond formation between two benzyl cyanide molecules.

X-ray structure investigation indicates a symmetrical structure. The C=N distances are smaller than usual, the Ti---N distances are very short, and the Ti---N---C angle differs only a little from 180°, which infers a heteroallene structure of the complex.  相似文献   


17.
Mechanisms of RN3 (R=CH3, CH3CH2, (CH3)2CH, (CH3)3C) dissociations are proposed based on CAS, MP2 and B3LYP methods. The energy gaps between the ground-state reactants RN3 and the intersystem crossing (ISC) points are only a little lower than respective potential energy barriers of the spin-allowed reactions, 1RN3 → 1RN + 1N2. The ISC point, therefore, is considered as a transition state of the spin-forbidden reactions, 1RN3 → 3RN + 1N2. The methods of IRC and topological analysis of electron density are used to explain and predict the thermal dissociation pathways of the reactions studied.  相似文献   

18.
The triplet state (32T) and the radical cation (2T+√) of 2,2′-bithiophene (2T) are characterized by pulse radiolysis in CCl4. Two main absorption bands at 360 and 420 nm are respectively attributed to 32T* and to 2T+√. The triplet, induced in an excited state through a Förster mechanism, undergoes a conformational rearrangement (k6=(6.8±0.9)×106 s−1). The radical cation is produced both through a resonance charge transfer and a second diffusional process; the two oxidizing species are respectively CCl4+√ and (CCl+3Cl)solv through the mediation of a singlet excited state, 12T*.  相似文献   

19.
The calculations reported here assign a charge qN = −0.52 electron units to the terminal nitrogen atoms in the azide ion and a value of 141.9 kJ mole−1 to the enthalpy of formation of the gaseous azide ion, ΔHf0(N3(g)). The total lattice potential energies are found to be: Epot(NaN3) = 725.1 kJ mole−1; Epot(KN3) = 650.7 kJ mole−1 and Epot(RbN3) = 632.1 kJ mole−1.  相似文献   

20.
Reaction of Cp*2TiR (R = CH3, neo-C5H11) with CO gives labile acyl compounds Cp*2TiCOR. The latter react with (CpMo(CO)3)2 to yield complexes Cp*2Ti(η2-COR)(μ-OC)MoCp(CO)2, which undergo acyl C---O band scission with concomitant formation of benzene derivatives at room temperature. The benzene derivatives are formed through ring expansion of the Cp* ligand by incorporation of the R---C fragment of the acyl group. The acyl oxygen is incorporated into a dimeric titanium oxo complex.  相似文献   

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