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11.
Padraic S. Nagle Amila Kahved?i? Thomas McCabe Isabel Rozas 《Structural chemistry》2012,23(2):315-323
We present the crystal structures of the chloride salts of the mono-guanidinium 1 (–CH2CH2– linker) and the bis-isouronium 2 (–O– linker) that have been resolved by us indicating that these compounds are diprotonated in the solid state as informed
by the counterions positions. To determine the pK
a values of these compounds as well as those of their analogues 3 (mono-2-aminoimidazolinium with a –CH2CH2– linker) and 4 (mono-guanidinium with a –O– linker), the corresponding UV–Vis titrations were carried out. Thus, in aqueous solution compounds
1, 3 and 4 were present as mono-cationic species while derivative 2 was a bis-cation. 相似文献
12.
Barsan MM Butler IS Gilson DF Moyer RO Zhou W Wu H Udovic TJ 《The journal of physical chemistry. A》2012,116(10):2490-2496
The vibrational spectra of the ternary metal hydride (deuteride) salts, A(2)MH(5) and A(2)MD(5), where A = calcium, strontium and europium and M = iridium(I) and rhodium(I), have been assigned using Raman, Fourier transform infrared, photoacoustic infrared, and inelastic neutron scattering spectroscopies and density functional theory (DFT) calculations. The wavenumbers of the infrared-active stretching vibrations depend upon the ionization energies of the central metal atom and the cation. The phase transition in calcium pentahydridoiridate(I) was studied as a function of temperature and pressure. 相似文献
13.
A protocol for the intramolecular Heck cyclization to afford 3,3‐diethyl‐4‐(methylene)‐1‐quinol‐2‐ones is described. We observed that the use of microwave irradiation increased the efficiency of the reaction. Several examples are presented which show the versatility of the reaction. 相似文献
14.
The synthesis and photophysical evaluation of three diaryl thiourea-based anion receptors (4–6) for comparison with their urea counterparts (1–3) is outlined. These anion receptors posses an acetamide functionality on one of the aryl groups and an electron-withdrawing CF3 group on the other. By varying the position of the acetamide group, in the o-, m- and p-positions of 4–6, respectively, the anion binding ability was both tuneable and found to be, in some cases, significantly different from that seen for the urea analogues 1–3. The binding affinities of the receptors 4–6, as well as the binding stoichiometries, were evaluated using UV–vis absorption spectroscopy in MeCN. However, these receptors were not sufficiently emissive to quantify the anion recognition using fluorescence. The results confirmed strong binding of these receptors to anions such as fluoride, acetate, phosphate, pyrophosphate and chloride. Nevertheless, the overall results obtained did not conform to the anticipated trends seen for 1–3, which is most likely due to the enhanced binding affinity of the thiourea analogues 4–6. The binding interactions were also investigated by using 1H NMR which confirmed that these receptors interacted with the anions in a stepwise manner, where the primary anion binding interaction occurred at the thiourea side, which led to an activation of the acetamide moiety towards the second anion binding interaction, an example of an allosteric activation mode. 相似文献
15.
John M. Adams Keith Martin Richard W. McCabe 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(6):663-674
Suitably modified smectite clays can be very selective catalysts for a wide range of organic reactions. While it has long been known that such materials can act as Bronsted and Lewis acids, it has been shown recently that they are also effective Diels-Alder catalysts. A selection of illustrative reactions is given which emphasises their wide range of use, their selectivity, and the ease of work-up after reaction. In each case, mechanistic information is presented, e.g., on the site of reaction (whether interlayer or surface), rate determining steps, etc. The regiochemical consequences of the restricted reaction space are stressed.Based on material presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986. 相似文献
16.
Terrence G. Vargo Daniel J. Hook Joseph A. Gardella Mary A. Eberhardt Anne E. Meyer Robert E. Baier 《Journal of polymer science. Part A, Polymer chemistry》1991,29(4):535-545
Recent work in our laboratories has fully characterized the surface region of a segmented poly(ether-urethane) (PEU) extending from the air/polymer interfacial region through bulk depths in the micron range. This characterization utilized energy and angle dependent Electron Spectroscopy for Chemical Analysis (ESCA), Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy (ATR–FTIR), and Comprehensive Wettability Profiling (contact angle using a homologous series of liquids) as defined by Zisman. In this study this same multi-analytical-technique approach is used to elucidate changes in these PEU surfaces induced through an H2O Radio Frequency Glow Discharge (RFGD) plasma. This investigation reports both qualitative and quantitative changes due to the modification treatments as well as the permanency of the changes effected on these surfaces through the plasma treatment. From our analyses, the amount of surface residing polyurethane (hard segment) is observed to increase due to a proposed plasma etching mechanism. Further, the addition of oxygen containing functionality is detected at the modified surfaces unique with respect to the unmodified PEU. These surface modifications which show large increases in wettability, are finally observed to be semi-permanent over a time period of 6 months. 相似文献
17.
J. H. McCabe 《The Ramanujan Journal》2009,19(1):95-105
A recently observed connection between some Padé approximants for the exponential series and the convergents of the simple continued fraction for e is established, leading to an alternative proof of the latter. Similar results for the simple continued fraction e
2,e
1/M
and e
2/M
, when M is a natural number greater than one, are derived.
相似文献
18.
Nonequilibrium molecular dynamics of a low-molecular-weight fluid (squalane) are compared with experimental measurements in both the linear (Newtonian) and nonlinear (non-Newtonian) regimes. The experimental and simulation data are shown to follow the same time-temperature superposition master curve. This represents the first comparison of the nonlinear rheology predicted by nonequilibrium molecular dynamics with experiment, and is thus the first experimental test of nonequilibrium molecular dynamics simulations in the nonlinear regime. 相似文献
19.
Ralph P. Cooney Martin W. Howard Merrick R. Mahoney Terrence P. Mernagh 《Chemical physics letters》1981,79(3):459-464
A mechanism is proposed for surface-enhanced Raman scattering for pyridine which explains the enhancement, the anodizalion “activation”, the significance of silver, the photographitization of coordinated pyridine and formate, the participation of surface roughness, and the irreversibly held yet liquid-like nature of surface pyridine. 相似文献
20.
Nitrogen-15 NMR data for a series of 21 triazolobenzodiazepines are presented, including 15N chemical shifts and substituent effects. The line assignments made by correlation to other model compounds were confirmed by a shift reagent and protonation study. A Yb(dpm)3 study on alprazolam showed that the molar shifts of the four nitrogens ranged from 35 to 150 ppm. 相似文献