نتایج جستجو برای: ionic bond
تعداد نتایج: 115031 فیلتر نتایج به سال:
Compared to conventional molecular solvents, the ionic liquid [b-3C-im][NTf(2)] was found to promote transimination reactions with up to ∼100-fold rate enhancement. This rate effect observed at ambient temperature might be explained by the fact that the ionic liquid displays weak Lewis acidity with very low, if any, nucleophilicity and its imidazolium cation is expected to interact by associati...
In a straightforward and fast protocol, a mixture of 1,3-dimethylimidazolium fluoride ([DMIM]F) and 1-butylimidazolium tetrafluoroborate ([Hbim]BF₄) efficiently catalyzed the reaction of epoxides with ketene silyl acetals (KSA) to give various γ-lactones under metal-free conditions. Diverse kinds of the desired γ-lactones were directly prepared with high regioselectivities and yields in a simpl...
The electronic structure of the ground state of monoxides MO and carbides MC2 with M an alkaline-earthmetal atom (Be to Ba) has been investigated. Bond energies, vibrational frequencies, dipole moments and equilibrium bond lengths have been calculated using a hybrid density functional method. To understand the bonding characteristics, the ELF (electron localization function) and the NBO (natura...
The dissociation of a water molecule in liquid water is the fundamental event in acid-base chemistry, determining the pH of water. Because of the short time scales and microscopic length scales involved, the dynamics of this autoionization have not been directly probed by experiment. Here, the autoionization mechanism is revealed by sampling and analyzing ab initio molecular dynamics trajectori...
We could show by means of dispersion-corrected DFT calculations that the interaction energy in protic ionic liquids can be dissected into Coulomb interaction, hydrogen bonding and dispersion interaction. The H-bond energy as well as the dispersion energy can be quantified to be 50 kJ mol(-1) each representing ten percent of the overall interaction energy. The dispersion interaction could be dis...
We have carried out an ab initio molecular dynamics study on the sulfur dioxide (SO2) solvation in 1-ethyl-3-methylimidazolium thiocyanate for which we have observed that both cations and anions play an essential role in the solvation of SO2. Whereas, the anions tend to form a thiocyanate- and much less often an isothiocyanate-SO2 adduct, the cations create a "cage" around SO2 with those groups...
Although it has been widely used as a feed supplement to reduce manure phosphorus pollution of swine and poultry, Aspergillus niger PhyA phytase is unable to withstand heat inactivation during feed pelleting. Crystal structure comparisons with its close homolog, the thermostable Aspergillus fumigatus phytase (Afp), suggest associations of thermostability with several key residues (E35, S42, R16...
علیرغم پیشرفتهای قابل توجه در زمینه ایجاد باند مناسب مواد ترمیمی همرنگ با نسج دندان ، بقای باند ایجاد شده از مسائل چالش برانگیز است. به نظر می رسد استفاده از عوامل ایجادکننده کراس لینک (مانند اسید تانیک و کلرهگزیدین) می تواند به حفظ و افزایش استحکام باند رزین- عاج کمک نماید. هدف از انجام این مطالعه،مقایسه اسیدتانیک و کلرهگزیدین بر استحکام باند برشی سیستم های ادهزیو etch&rinse و self etch در عا...
The ionic title compound, C(12)H(28)P(+)·C(18)HBF(15)O(-), was obtained by the stoichiometric reaction of (t)Bu(3)P, B(C(6)F(5))(3) and water in toluene. A weak P-H⋯O hydrogen bond is observed in the crystal structure.
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