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991.
I. V. Aristov O. V. Bobreshova O. Yu. Strel'nikova 《Russian Journal of Electrochemistry》2002,38(5):567-569
In mixed aqueous solution of glycine and L-lysine the ionization of both amino acids increases due to the proton transfer from glycine zwitterion to lysine zwitterion. This is manifested by a considerable nonlinear (pairwise interaction of amino acids) increase in the mixed solution electroconductivity at high amino acid concentrations. The solution pH varies negligibly, as the amino acids in aqueous solutions demonstrate buffering. The refraction coefficient additively depends on glycine and L-lysine concentrations. 相似文献
992.
O. V. Shishkin 《Russian Chemical Bulletin》1996,45(8):1833-1835
Molecular and electronic structures of 1,2-dihydropyridine, 1,2- and 1,6-dihydropyrimidine, and their oxo, imino, and methylene derivatives were studied by the semiempirical quantum-chemical AM1 method. In all compounds, the heterocycle exhibits a high conformational flexibility. The transition from a planar equilibrium conformation to a distorted sofa conformation with the =C-NH-C-C(N)= torsion angle of ±20° causes an increase in the energy by less than 1.7 kcal mol–1. All molecules have similar -electronic structures, which, apparently, determines the similarity in their conformational behavior. The bending strain and the nonaromatic character of the cyclic -system are the factors that stabilize the nonplanar conformation of the ring in unsubstituted dihydroazines and ylide derivatives, respectively.Translated fromIzvestiva Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1934–1937, August, 1996. 相似文献
993.
Abstract— High concentrations of organic chromophores, in particular pyrene, were found to incorporate into the cluster network of water swollen Nation. The vibrational structure of the fluorescent molecule and its fluorescence lifetime were used to probe the location of pyrene in this structure. Strong heavy-atom induced room temperature phosphorescence was observed from the chromophore in the water swollen membrane. Excimer formation in tm-butanol swollen Nation was observed and was utilized to estimate the micro viscosity in this system. 相似文献
994.
Emile Cherbuliez B. R. Behler O. Espejo E. Frankenfeld S. Jaccard J. Rabinowitz 《Helvetica chimica acta》1967,50(3):979-985
N-Aryl(or aralkyl or alkyl)carbamoyl-aminoalkyl phosphoric monoesters have been prepared by the reaction of isocyanates R′-N?C?O on the corresponding amino-alkylphosphoric monoesters H2N? R? OPO3H2 in the presence of 2 equivalents of NaOH. The rates of scission of the phosphoric monoester group and occasionally of the phenylcarbamoylamino group of these monoesters have been studied at 100°, in solutions 0.1M in ester and at various pH. 相似文献
995.
O. S. Chizhov B. A. Dmitriev B. M. Zolotarev A. Ya. Chernyak N. K. Kochetov 《Journal of mass spectrometry : JMS》1969,2(10):947-952
The trifluoroacetyl derivatives of alditols are convenient compounds for mass spectrometric investigation as they are easily obtainable and highly volatile. They show simple fragmentation patterns with intensive peaks in the high mass range. Trifluoroacetates of alditols may be used for detection and location of deoxy groups in the molecule. 相似文献
996.
The vibrational frequencies and corresponding normal mode assignments of urazole are examined theoretically using the Gaussian98 set of quantum chemistry codes. All normal modes were successfully assigned to one of eight types of motion (N--H stretch, C=O stretch, C--N stretch, N--N stretch, N--H bend, C=O bend, N--C--N bend, ring torsion) utilizing the C2 symmetry of the molecule. The molecular orbitals of urazole are examined. The simultaneous double inversion of the amine groups in urazole is also examined. 相似文献
997.
G. Lligadas J. C. Ronda M. Gali U. Biermann J. O. Metzger 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):634-645
Oligomeric polyether polyols were obtained through the acid‐catalyzed ring‐opening polymerization of epoxidized methyl oleate and the subsequent partial reduction of ester groups to give primary alcohols. The oligomers were characterized with titration, spectroscopic techniques (Fourier transform infrared and nuclear magnetic resonance), matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, size exclusion chromatography, and differential scanning calorimetry. Depending on the degree of reduction, polyols of different hydroxyl content values were obtained and were reacted with 4,4′‐methylenebis(phenyl isocyanate) to yield polyurethanes. These materials, which were characterized by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis, could behave as hard rubbers or rigid plastics. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 634–645, 2006 相似文献
998.
Conclusions 1,3,5-Diazaphosphorinanes react with borane yielding, depending on the nature of the substituents at the ring atoms, complexes with two or three borane molecules and the products of ring opening at the C-N bonds of the P-C-N and N-C-N fragments.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1375–1379, June, 1989. 相似文献
999.
O. Hromatka M. Knollmüller D. Binder 《Monatshefte für Chemie / Chemical Monthly》1968,99(3):1117-1123
Zusammenfassung Beim Einwirken von Perbenzoesäure auf 6-Phenyl-3,4-dihydro-1H-2,1,5-benzothiadiazocin-2,2-dioxide erhält man die 5-Oxide, die sich durch Bestrahlen mit UV-Licht in die entsprechenden Oxazirino[2,3-e][2,1,5]benzothiadiazocine umwandeln lassen.
1. Mitt. dieser Reihe:O. Hromatka, D. Binder undM. Knollmüller, Mh. Chem.99, 1062; 2. Mitt.:O. Hromatka, M. Knollmüller, D. Binder, H. Deschler undG. Schöllnhammer, Mh. Chem.99, 1111 (1968). 相似文献
The reaction of perbenzoic acid with 6-phenyl-3,4-dihydro-1H-2,1,5-benzothiadiazocine-2,2-dioxides leads to the corresponding 5-oxides, which in turn can be converted to oxazirino-[2,3-e][2,1,5]benzothiadiazocines by uv-irradiation.
1. Mitt. dieser Reihe:O. Hromatka, D. Binder undM. Knollmüller, Mh. Chem.99, 1062; 2. Mitt.:O. Hromatka, M. Knollmüller, D. Binder, H. Deschler undG. Schöllnhammer, Mh. Chem.99, 1111 (1968). 相似文献
1000.
A comparison of the performance of narrow-bore (2.1-mm i.d.) and standard-bore (4.6-mm i.d.) analytical silica columns having the same length is completed for the resolution of alpha-, beta-, gamma-, and delta-tocopherol. The studies are performed on high-performance liquid chromatographic equipment with minimum extracolumn contribution. Column permeabilities are 1.16 x 10(-9) and 2.48 x 10(-9) cm2 for narrow and standard bore, respectively. The narrow-bore column gives up to a 7 times increase in sensitivity compared with a standard-bore column at equivalent running times for the analytes. Approximately one-third solvent savings can be achieved with the narrow-bore column. Theoretical plates of the standard-bore column are higher than that of the narrow-bore column. 相似文献