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11.
Ben-Ami Feit Eri Heller Albert Zilkha 《Journal of polymer science. Part A, Polymer chemistry》1966,4(6):1499-1508
The anionic oligomerization of methacrylonitrile by alcoholic solutions of sodium alkoxide in dimethyl sulfoxide, methanol and ethanol was studied. The DP of the oligomers was directly proportional to the monomer concentration and inversely proportional to the alcohol concentration, in accordance with the equation DP = K[MAN]/[ROH], K being equal to Kp/Ktr. The value of K in DMSO (with sodium methoxidemethanol) was 2.9 ± 0.2, in methanol was 1.5 ± 0.1, and in ethanol (with sodium ethoxide as initiator) was 1.9 ± 0.1. The physical properties of the oligomers are given. 相似文献
12.
Eric J. Heller 《Chemical physics letters》1982,90(6):484-485
A simple analysis of the competition between the alternative channels of atom and excitation transfer in collisions of metastable rare-gas atoms with halogens is presented. The intervention of potential surfaces correlating with highly excited Rydberg states lying just below the limit of the molecular cation as well as those which correlate with the anion provides a qualitative rationale for much current experimental data. 相似文献
13.
Donald F. Heller 《Chemical physics letters》1979,61(3):583-587
The apparent simplicity of polyatomic overtone spectra and the conceptual utility of local modes are considered. The form and basis-set-dependence of the dipole moment operator are discussed and a criterion given for overtone spectra to be well described within a local mode picture. Caution is needed in making dynamical inferences based on agreement between overtone and local mode line positions. 相似文献
14.
Martin Sukopp Luciana Marinelli Markus Heller Trixi Brandl SimonL. Goodman ReinhardW. Hoffmann Horst Kessler 《Helvetica chimica acta》2002,85(12):4442-4452
The (3R,5S,6E,8S,10R)‐11‐amino‐3,5,8,10‐tetramethylundec‐6‐enoic acid (ATUA; 1 ), which was designed as a βII′‐turn mimic according to the concepts of allylic strain and 2,4‐dimethylpentane units, was incorporated into a cyclic RGD peptide. The three‐dimensional structure of cyclo(‐RGD‐ATUA‐) (=cyclo(‐Arg‐Gly‐Asp‐ATUA‐)) 4 in H2O was determined by NMR techniques, distance geometry calculations and molecular‐dynamics simulations. The RGD sequence of 4 shows high conformational flexibility but some preference for an extended conformation. The structural features of the RGD sequence of 4 were compared with the RGD moiety of cyclo(‐RGDfV‐) (=cyclo(‐Arg‐Gly‐Asp‐D ‐Phe‐Val‐)). In contrast to cyclo(‐RGDfV‐), which is a highly active αvβ3 antagonist and selective against αIIbβ3, cyclo(‐RGD‐ATUA‐) shows a lower activity and selectivity. The structure of the ATUA residue in the cyclic peptide resembles a βII′‐turn‐like conformation. Its middle part, adjacent to the C?C bond, strongly prefers the designed and desired structure. 相似文献
15.
Oxygen is electroreduced to water on a carbon cathode coated with wired bilirubin oxidase in a pH 7.4 0.15 M NaCl phosphate buffer solution at 37 °C at much lesser polarization than it is on a pure platinum cathode in 0.5 M H2SO4. While the wired bilirubin oxidase cathode operates for over a week in the aerated or oxygenated buffer solution, it is degraded rapidly when in serum. We reported earlier that in the presence of O2 an intermediate product of the electrooxidation of urate, which is a normal serum component, irreversibly damages the wired bilirubin oxidase and also reported that the electrocatalyst is irreversibly damaged, in the absence of urate, when it is brought, by disconnecting the electrode, to the O2/H2O half cell potential at pH 7.4. Here we report that a) dissolved bilirubin oxidase is irreversibly and rapidly damaged by urate in the presence of O2; and b) that the immobilized wired bilirubin oxidase electrocatalyst is not only irreversibly deactivated by urate in the presence of O2 in a few hours, but is initially reversibly deactivated, in 1 min or less, by the urate in the presence of O2. 相似文献
16.
From the bulbs of Eucomis punctata L'Hérit. (Liliaceae) and of a hitherto undefined species of Eucomis a new optically active phenolic carboxylic acid, eucomic acid, was isolated. Structure 1 was assigned on the basis of chemical and spectral evidence. The absolute configuration of eucomic acid was determined by its correlation with piscidic acid ((2 R, 3 S)-2-(4′-hydroxybenzyl)-tartaric acid) ( 8 ). Consequently, eucomic acid is (R)-(?)-2-(4′-hydroxybenzyl)-malic acid ( 1 ). For the stereospecific synthesis, methyl cis-p-methoxybenzylidene-succinic acid ( 22 ) was transformed into the γ-lactone 24 which, by catalytic hydrogenolysis, yielded (±)-2-(4′-hydroxybenzyl)-malic acid 1-methyl ester ( 27 ). Resolution with (?)-quinine led to the enantiomeric acids 29 and 30 . The methyl ester of the levorotatory enantiomer 30 was identical with the dimethyl ester 3 of 4′-O-methyl-eucomic acid. 相似文献
17.
Various mono- and disubstituted 2,2'-bipyridines were synthesized in high yields and multigram scales utilizing Stille-type coupling procedures. The corresponding bromo-picoline and tributyltin-picoline building blocks were prepared from commercially available amino-picoline compounds. As first examples of metal complexes, 4,5'-dimethyl-2,2'-bipyridine was reacted with copper(II) and iron(II) ions and investigated as catalyst in ATRP. 相似文献
18.
Treatment of an acetonitrile solution of CuI with 1, 7‐dithia‐18‐crown‐6 (1, 7‐DT18C6) at 100°C affords the coordination polymer 1[(CuI)2(1, 7‐DT18C6)2] ( 1 ) in which 1, 7‐DT18C6 ligands bridge (CuI)2 rings into double chains. 1D polymers of the type 1[M{(Cu3I4)(1, 7‐DT18C6)}] (M = K, 2 ; M = Cs, 3 ) can be isolated under similar conditions in the presence of respectively KI and CsI. Both contain bridging heptacyclic [Cu6I8]2— units but crystallise in different space groups, namely P1 and C2/m. The cesium cation of 3 is markedly displaced from the best plane through the thiacrown ether donor atoms. Reaction of 1, 7‐DT18C6 with CuSCN in the presence of NaSCN yields 2[{Na(CH3CN)2} {(CuSCN)2(1, 7‐DT18C6)}][Cu(SCN)2] ( 4 ), in which 1[(CuSCN)2] double chains are linked through macrocycles into sheets. Infinite 1[{Cu(SCN)2}—] chains compensate the charge of the Na+ cations. Complex 1 can imbibe 0.90 mol CsNO3 per mol of 1, 7‐DT18C6 pairs. 相似文献
19.
20.