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991.
Silvia Dorn Peter Eggenberg Michael R. C. Gerstenberger Alois Haas Ulrich Niemann Peter Zobrist 《Helvetica chimica acta》1979,62(5):1442-1450
(Perhalomethylthio)heterocycles. X 1 IX. Mitt.: s. [1]. . Acid-catalyzed substitutions on (perchlorofluoromethylthio)pyrroles and their agro-biological activities In the presence of C4F9SO3H the (perhalomethylthio)pyrroles 1a–c react with Cl3?nFnCSCl (n = 1–3) to give mixtures of the 2,5- and 2,4-disubstituted pyrroles 2a–f and 3a–h . 2a and 3a react with CF3SCl (catalyst CF3SO3H) yielding 2,3,5-tris (trifloromethylthio)pyrrole ( 4a ), which under similar conditions reacts further to give 2,3,4,5-tetrakis (trifluoromethylthio)pyrrole ( 5 ). As a by-product during the conversion of 3a to 4a 2,3,4-tris (trifluoromethylthio)pyrrole ( 4b ) is formed. The pyrroles 2a , 4a and 5 form the mercury salts 6a–c ; compound 5 yields also a silver salt 7 . The 1H- and 19F-NMR. spectra are discussed and the agro-biological properties of the compounds investigated. 相似文献
992.
The acidity functions of aqueous trifluoroacetic and trifluoromethanesulphonic acid mixtures, and aqueous hexafluoropropane-2, 2-diol solutions, have been determined by differential pulse polarography. The apparent shift of the half-wave potential for the ferrocene—ferricinium couple, as the solvent composition is changed, is used to indicate the change in potential of a glass electrode; acidity is measured as the HGF acidity function. The densities of two of these solvent systems as a function of composition are also reported. Trifluoromethanesulphonic acid—water mixtures represent the strongest aqueous acid solvent system so far studied. 相似文献
993.
The principal decomposition routes of molecular ions of cis, cis-3,4-dimethyl-2-4-hexadiene, cis, trans-3,4-dimethyl-2,4-hexadiene, cis-1,2,3,4-tetramethylcyclobutene and trans-1,2,3,4-tetramethylcyclobutene were studied using ion kinetic energy spectroscopy. Evidence indecates that loss of radicals from [M]+· appears to proceed via an electronically excited state, while loss of a neutral molecule appears to involve complete equilibration of structure within the system, or may involve both ground state and excited state pathways. 相似文献
994.
James J. Gallagher Edward K. Chess Saleh M. Arghestani Michael L. Gross 《Journal of mass spectrometry : JMS》1983,18(3):118-126
Mechanisms for decomposition of 1- and 2-phenyltetralins were investigated using low resolution mass spectrometry and metastable ion techniques. Four primary decompositions were observed for 1-phenyltetralin radical cations: (1) the loss of C6H6 via a 1,4-elimination; (2) the elimination of ethene via competing losses from carbons 3 + 4 and carbons 2 + 3; (3) the loss of C8H8, probably through a stepwise Diels-Alder cycloreversion to expel styrene; and (4) the loss of methyl radical involving carbon 2 and possibly carbon 4. Three major decompositions were observed for 2-phenyltetralin radical cations: (1) the loss of C8H8, possibly through a Diels-Alder cycloreversion to expel styrene; (2) the loss of C6H6 via a 1,3 elimination; and (3) the loss of methyl radical from carbon 1. Various exchange reactions occur prior to these losses, but they proved to be incomplete even for metastable ions. 相似文献
995.
Michael Eyer Karl Schlögl Michael Widhalm 《Monatshefte für Chemie / Chemical Monthly》1984,115(12):1429-1442
Chiral title compounds have been resolved by medium pressure liquid chromatography (MPLC) on triacetylcellulose in ethanol. Whereas a quantitative separation was achieved for16 and20, a recycling technique had to be applied to1,4,6,10 and15 leading to a 100% e.e. for1,6 and15 and to ca. 60% e.e. for4 and10.An unambiguous assignment of the chirality (+)-(R)
a
-(S)
m
for tricarbonylchromium-6,6-dimethyl-diphenicacid dimethylester (4) was deduced both from the photochemical decomplexation to (-)-5 with the known chirality (R)
a
(whose e.e. was determined by MPLC on triacetylcellulose) and by comparison of the1H-n.m.r. spectra of4 and5 thereby proving the structure 4 for the former.Other chiralities both for mono and bis(tricarbonylchromium)biphenyl complexes were established by chemical correlations and comparison of the CD spectra with those of key compounds.
Herrn Prof. Dr.H. Tuppy mit besten Wünschen zum 60. Geburtstag gewidmet. 相似文献
996.
-The luminescence at 1.27 μm from the 3 →→1 δg transition of the oxygen molecule has been detected from a variety of liquid systems. A Q-switched laser delivering pulses of 532 nm light was the excitation source, a germanium photodiode was the detector and substituted porphyrins were used as photosensitizers. Protio- and deutero- forms of several solvents were studied and the singlet oxygen lifetimes determined directly agreed well with published values. Tδ in D2 O was found to be 55 μs and, by extrapolation from a series of H2 O - D2 O mixtures, a value of 3.3 μs was obtained for Tδ in H2 O. The technique was shown to be useful in measuring Tδ values in several microheterogeneous systems such as surfactant micelles, vesicles and human serum albumin. 相似文献
997.
J.E. House Jr. G.L. Jeyaraj David A. Engel Michael D. Lowery 《Thermochimica Acta》1983,70(1-3):189-193
The decomposition of Li2S2O6·2 H2O, Na2S2O6·2 H2O, and MgS2O6·7 H2O has been studied using TG and DTG. Both sodium and lithium dithionates dehydrate in one step. Magnesium dithionate dehydrates in three separate steps. All three of the dithionates undergo further decomposition and lose sulfur dioxide to give stable sulfates. Kinetic parameters are presented for these reactions. 相似文献
998.
Abstract— The rate constant for total quenching of singlet oxygen by ascorbic acid has been determined using the inhibition of the bleaching of 9, 10-dimethylanthracene by AA in pyridine. The rate constant was 8.4 × 10-6 M -1 s-1 , as determined photochemically, and 1.06 10-7 M -1 s-1 as determined in a dark reaction. 相似文献
999.
David Wei Wang Michael M. Fisher 《Journal of polymer science. Part A, Polymer chemistry》1983,21(3):671-677
A two-phase polycondensation reaction was used to prepare high molecular weight linear poly-(amino-s-triazine)s from aminodichloro-s-triazines and diamines. These polymers contain a high concentration of melamine-type units in the polymer backbone. Molded specimens exhibited good mechanical properties and resistance to organic solvents. Dimethyl substitution at the exocyclic amino group led to a significant reduction in indentation resistance, strength, and modulus. 相似文献
1000.