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61.
Thermal motion of CH4+ is investigated by performing an ab initio molecular dynamics method with the second-order M?ller-Plesset (MP2)/6-311G** force field. In the trajectories obtained at 400 K, we have observed rapid interconversion behavior of the geometrical parameters of CH4+ with the frequency of 0.6/ps, where the C-H pair forming the small angle around 55 degrees is switched to another pair on subpicosecond time scale. The switching patterns are found to be classified into the following two types. Type 1: one C-H of the small angled C-H pair is switched to one C-H of the other C-H pair. Type 2: the small angled C-H pair is switched to the other C-H pair, which has been newly observed in the present ab initio MD calculation. The four C-H bonds of CH4+ are characterized by the long and short C-H bonds in a time region of the trajectories, and also for the time-evolution of C-H bonds such interconversion behavior is observed. The switching patterns of the geometrical parameters are compared with those in the interconversion scheme between six equivalent C2v symmetry structures of CH4+ [Paddon-Row, M. N. et al., J Am Chem Soc 1985, 107, 7696]. We have also investigated the electronic energy fluctuation due to thermal motion of CH4+. The standard deviation of total electronic energy at 400 K is evaluated to be 1.2 kcal/mol. 相似文献
62.
C. Y. Zhu R. M. Izatt J. S. Bradshaw N. K. Dalley 《Journal of inclusion phenomena and macrocyclic chemistry》1992,13(1):17-27
Equilibrium constant (K), enthalpy change (H), and entropy change (S) values have been determined calorimetrically at 25°C in 90%MeOH 10%H2O (v/v) for the interactions of pyridino-18-crown-6 (P18C6) and diketopyridino-18-crown-6 (K2P18C6) with perchlorate salts of ammonium, benzylammonium,-phenylethylammonium,-phenylethylammonium, and-(1-naphthyl)ethyl-ammonium cations. The crystal structure of the complex of P18C6 with benzylammonium perchlorate was determined by X-ray crystallography. The1H 1D and 2D NMR spectra of some of these complexes were used to elucidate their structural features in solution. The logK values for the interaction of the ammonium cations with P18C6 are larger than those with K2P18C6, probably due to the higher degree of structural flexibility of P18C6. Ligand K2P18C6 displays appreciable - interaction with the-(1-naphthyl)ethylammonium cation, but not with the-phenylethylammonium cation.- interaction between ligand and cationSupplementary Data relating to this article are deposited with the British Library as Supplementary Publication No SUP 00000 (22 pages) 相似文献
63.
A. Lévai 《Monatshefte für Chemie / Chemical Monthly》1995,126(11):1245-1251
Summary 3-Aroyl-4-aryl-2-pyrazolines (21–40) have been synthesized by the reaction of ,-unsaturated ketones (1–20) with diazomethane. These 2-pyrazolines gave -methyl-,-unsaturated ketones (41–46) on thermal denitrogenation.Dedicated to Prof. Dr.F. Sauter on the occasion of his 65th birthday 相似文献
64.
Alan C. Hopkinson Min H. Lien Imre G. Csizmadia Keith Yates 《Theoretical chemistry accounts》1980,55(1):1-14
The geometries of the 2-aminoethyl cation and the isomeric protonated aziridine have been optimized using ab initio molecular orbital calculations employing the split-valence shell 4-31G basis set. The protonated aziridine is computed to be the more stable ion by 46.5 kcal/mole (4-31G level) and 44.9 kcal/mole (double-zeta basis set). The profile to interconversion is found to have a barrier of less than 15 kcal/mole (relative to the 2-aminoethyl cation) and this profile is compared with those computed for the similar ions XCH2CH
2
+
where X=OH, F, SH and Cl. 相似文献
65.
《中国科学B辑(英文版)》2007,(5)
The X-ray crystal structures of (NH4)2(15-crown-5)3[Cu(mnt)2] (1) and (NH4)2(benzo-15-crown-5)4- [Cu(mnt)2]·0.5H2O (2) were determined. Two single crystals are composed of distinct structures of ammonium-crown ether supramolecular cation and [Cu(mnt)2]2? anion. The triple-decker dication in complex 1 and a sandwich dimmer in complex 2 were observed. X-Band EPR studies on the single crystals of both complex 1 and complex 2 have been carried out at room temperature, which revealed that complex 2 showed a perfect hyperfine structure of Cu whereas that of complex 1 could not be observed. The principal values and direction cosines of the principal axes of the g and A tensors were computed by a least-squares fitting procedure. The spin density of Cu(II) was estimated according to the principal values of the A tensors and compared well with the results calculated based on DFT method. 相似文献
66.
Rieko Furuyama Junji Saito Sei-ichi Ishii Makoto Mitani Shigekazu Matsui Yasushi Tohi Haruyuki Makio Naoto Matsukawa Hidetsugu Tanaka Terunori Fujita 《Journal of molecular catalysis. A, Chemical》2003,200(1-2):31-42
This contribution reports ethylene and propylene polymerization behavior of a series of Ti complexes bearing a pair of phenoxy–imine chelate ligands. The bis(phenoxy–imine)Ti complexes in conjunction with methylalumoxane (MAO) can be active catalysts for the polymerization of ethylene. Unexpectedly, this C2 symmetric catalyst produces syndiotactic polypropylene. 13C NMR spectroscopy has revealed that the syndiotacticity arises from a chain-end control mechanism. Substitutions on the phenoxy–imine ligands have substantial effects on both ethylene and propylene polymerization behavior of the complexes. In particular, the steric bulk of the substituent ortho to the phenoxy–oxygen is fundamental to obtaining high activity and high molecular weight for ethylene polymerization and high syndioselectivity for the chain-end controlled propylene polymerization. The highest ethylene polymerization activity, 3240 kg/mol-cat h, exhibited by a complex having a t-butyl group ortho to the phenoxy–oxygen, represents one of the highest reported to date for Ti-based non-metallocene catalysts. Additionally, the polypropylene produced exhibits a Tm, 140 °C, and syndioselectivity, rrrr 83.7% (achieved by a complex bearing a trimethylsilyl group ortho to the phenoxy–oxygen) that are among the highest for polypropylenes produced via a chain-end control mechanism. Hence, the bis(phenoxy–imine)Ti complexes are rare examples of non-metallocene catalysts that are useful for the polymerization of not only ethylene but also propylene. 相似文献
67.
A. D. Dilman D. E. Arkhipov P. A. Belyakov M. I. Struchkova V. A. Tartakovsky 《Russian Chemical Bulletin》2006,55(3):517-522
Reactions of tris(pentafluorophenyl)silanes RSi(C6F5)3 with salicylaldehyde and secondary amines were studied. The reactions afforded α-pentafluorophenyl-substituted amines. Silanes
RSi(C6F5)3 (R = Me, Ph, C6F5, CH2CH=CH2, and CH=CH2) were found to be efficient reagents for transfer of the C6F5 group to the iminium cation generated from salicylaldehyde and amine. However, tris(pentafluorophenyl)phenylethynyl-and tris(pentafluorophenyl)silanes
were not able to serve as a source of a fluorinated substituent because of competitive transfer of acetylenide fragment or
hydride.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 498–503, March, 2006. 相似文献
68.
69.
This paper reports the results on a study of ion chromatography (IC) behaviour on strong cationic exchange column of CH3-(CH2)n−1-NH2 (n=1-6) type linear monoamines. The eluents were mixtures of HCl-NaCl, HNO3-NaNO3, HClO4-NaClO4, H2SO4-Na2SO4, HClO4-NaClO4-CH3CN. Amines were revealed with an amperometric detector. The influence of different counter-ions on retention factors, k′, is discussed. Relationships between k′ and pE (E=sum of Na+ and H+ concentrations), and length of alkylic chain, and sensitivity coefficient S, are reported and discussed. The addition of acetonitrile (ACN) in the eluent was also taken into account. Suitable considerations are derived from these data. An example of monoamines separation is given. 相似文献
70.
Shin-ichi NayaMakoto Nitta 《Tetrahedron》2003,59(23):4157-4165
The synthesis and properties of a novel type of bis(heteroazulen-3-yl)methyl cations, bis(2-oxo-2H-cyclohepta[b]furan-3-yl)methyl cation salt and nitrogen analogues, (9a-c·PF6−) and (9a-c·BF4−), as well as bis(heteroazulen-3-yl)ketones (12a-d) are studied. The synthetic method was based on a TFA-catalyzed electrophilic aromatic substitution on the heteroazulenes (6a-d) with paraformaldehyde to afford the corresponding disubstituted methane derivatives 7a-d, followed by oxidative hydrogen abstraction with DDQ, and subsequent exchange of the counter-anion by using aq. HPF6 or aq. HBF4. In addition, the reaction of 7a-d with 2.2 equiv. amounts of DDQ afforded carbonyl compounds 12a-d. The delocalization of the positive charge of 9a-c was evaluated by the 1H and 13C NMR spectral data. The thermodynamic stability of cations 9a-c was evaluated to be in the order 9a<9b<9c on the basis of their reduction potentials measured by cyclic voltammetry (CV) and pKR+ values (2.6-10.3) obtained spectrophotometrically. The reduction waves of cations 9a-c were irreversible, suggesting the dimerization of the radical species generated by one-electron reduction. This was demonstrated by the reduction of 9a·BF4− with Zn powder to give dimerized product 14a. In addition, the quenching of 9a·BF4− with MeOH/NaHCO3 gives ether derivative 15a, which is proposed for the precursor for synthesizing tris(heteroazulene)-substituted methyl cations bearing two different heteroazulene-units. 相似文献