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51.
Stephen Bell Xiaodong Zhu Gamil A. Guirgis James R. Durig 《Journal of Molecular Structure》2002,616(1-3):135-158
The infrared spectra (3500–50 cm−1) of the gas and solid and the Raman spectra (3500–50 cm−1) of the liquid and solid have been recorded for 2-hexyne, CH3–CC–CH2CH2CH3. Variable temperature studies of the infrared spectrum (3500–400 cm−1) of 2-hexyne dissolved in liquid krypton have also been recorded. Utilizing four anti/gauche conformer pairs, the anti(trans) conformer is found to be the lower energy form with an enthalpy difference of 74±8 cm−1 (0.88±0.10 kJ/mol) determined from krypton solutions over the temperature range −105 to −150 °C. At room temperature it is estimated that there is 42% of the anti conformer present. Equilibrium geometries and energies of the two conformers have been determined by ab initio (HF and MP2) and hybrid DFT (B3LYP) methods using a number of basis sets. Only the HF and DFT methods predict the anti conformer as the more stable form as found experimentally. A vibrational assignment is proposed based on the force constants, relative intensities, depolarization ratios from the ab initio and DFT calculations and on rotational band contours obtained using the calculated equilibrium geometries. From calculated energies it is shown that the CH3 group exhibits almost completely free rotation which is in agreement with the observation of sub-band structure for the degenerate methyl vibrations from which values of the Coriolis coupling constants, ζ, have been determined. The results are compared to similar properties of some corresponding molecules. 相似文献
52.
The reaction of CCl2F2 (CFC 12) with hydrogen has been studied on a Pt/-Al2O3 catalyst containing 0.5, 2 and 5 wt % of Pt at a temperature of 300°C and on 2% Pt at other temperatures. The product selectivity (distribution), and the extent of conversion, was shown to be highly dependent both on the metal coverage and on the temperature. 相似文献
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Danielson JW Zuroski KE Twohy C Thompson RD Bell E McClure F 《Journal of AOAC International》2000,83(1):145-155
Sporicidal test results obtained from carriers inoculated with 4 types of defined Bacillus subtilis spore preparations were compared with the standard AOAC sporicidal test using soil extract nutrient broth (SENB) B. subtilis 19659 spores. Recoveries of spores inoculated on penicylinders from B. subtilis clean spores (washed and suspended in water) and B. subtilis 19659 spores inoculated from culture filtrates according to the AOAC method were compared. Spores were exposed to 6 concentrations (0.5-3.0% w/v) of glutaraldehyde in phosphate buffer (pH 7.5) for 10 h. Concentrations were established by titrimetry and liquid chromatography. Recoveries of surviving spores were determined for 3 types of clean B. subtilis var. niger preparations, one clean B. subtilis 19659 preparation, and the SENB B. subtilis 19659 filtrates. Spore carriers, inoculated by the standard AOAC protocol, resulted in as much as a 2-log number difference in runs 1-12, but not more than 0.5 log number for each clean spore preparation. The SENB spores varied most in resistance to glutaraldehyde, with no growth in recovery media from 3 different batches of 1, 1.5, and 2% glutaraldehyde. Separate batches of SENB preparations of B. subtilis 19659 were resistant and destroyed by 1.0% glutaraldehyde, with 3.98 and 6.0 log numbers of spores on penicylinders, respectively. Clean spore preparations of B. subtilis 19659 on porcelain penicylinders were more resistant to glutaraldehyde than were SENB spores. Nutrient agar/Mg/Ca and nutrient agar/Mg spore preparations of B. subtilis var. niger showed the most uniform resistance to glutaraldehyde. Spores with calcium added showed increased resistance to glutaraldehyde. B. subtilis 19659 spores from the Columbia broth spore preparation were the most resistant and were recovered after exposure to 3.0% glutaraldehyde. 相似文献
58.
Julie L. S. Bell David J. Wesolowski Donald A. Palmer 《Journal of solution chemistry》1993,22(2):125-136
The dissociation quotients of formic acid were measured potentiometrically from 25 to 200°C in NaCl solutions at ionic strengths of 0.1, 0.3 1.0, 3.0, and 5.0 mol-kg–1. The experiments were carried out in a concentration cell with hydrogen electrodes. The resulting molal acid dissociation quotients for formic acid, as well as a set of infinite dilution literature values and a calorimetrically-determined enthalpy of reaction, were fitted by an empirical equation involving an extended Debye Hückel term and seven adjustable parameters involving functions of temperature and ionic strength. This regressional analysis yielded the following thermodynamic quantities for 25°C: logK=–3.755±0.002, Ho=–0.09±0.15 kJ-mol–1, So=–72.2±0.5 J-K–1-mol–1, and C
p
o
=–147±4 J-K–1-mol–1. The isocoulombic form of the equilibrium constant is recommended for extrapolation to higher temperatures. 相似文献
59.
[reaction: see text] The reaction of CH(4) with CO(2) has been performed in anhydrous acids using VO(acac)(2) and K(2)S(2)O(8) as promoters. NMR analysis establishes that the primary product is a mixed anhydride of acetic acid and the acid solvent. In sulfuric acid, the overall reaction is CH(4) + CO(2) + SO(3) --> CH(3)C(O)-O-SO(3)H. Hydrolysis of the mixed anhydride produces acetic acid and the solvent acid. When trifluoroacetic acid is the solvent, acetic acid is primarily formed via the reaction CH(4) + CF(3)COOH --> CH(3)COOH + CHF(3). 相似文献
60.
Dr. James P. Dombrowski Dr. Micah S. Ziegler Dr. Neelay M. Phadke Erum Mansoor Dr. Daniel S. Levine Dr. Ryan J. Witzke Prof. Dr. Martin Head-Gordon Prof. Dr. Alexis T. Bell Prof. Dr. T. Don Tilley 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):307-315
Anionic molecular models for nonhydrolyzed and partially hydrolyzed aluminum and gallium framework sites on silica, M[OSi(OtBu)3]4− and HOM[OSi(OtBu)3]3− (where M=Al or Ga), were synthesized from anionic chlorides Li{M[OSi(OtBu)3]3Cl} in salt metathesis reactions. Sequestration of lithium cations with [12]crown-4 afforded charge-separated ion pairs composed of monomeric anions M[OSi(OtBu)3]4− with outer-sphere [([12]crown-4)2Li]+ cations, and hydroxides {HOM[OSi(OtBu)3]3} with pendant [([12]crown-4)Li]+ cations. These molecular models were characterized by single-crystal X-ray diffraction, vibrational spectroscopy, mass spectrometry and NMR spectroscopy. Upon treatment of monomeric [([12]crown-4)Li]{HOM[OSi(OtBu)3]3} complexes with benzyl alcohol, benzyloxide complexes were formed, modeling a possible pathway for the formation of active sites for Meerwin–Ponndorf–Verley (MPV) transfer hydrogenations with Al/Ga-doped silica catalysts. 相似文献