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901.
T. M. Gorrie S. Kalyana Raman H. K. Rouette Heinrich Zollinger 《Helvetica chimica acta》1973,56(1):175-195
An NMR. investigation of the state of formaldehyde in acidic solutions has been carried out. Solutions of DCl/D2O/CD3COOD containing two sources of formaldehyde, i.e. paraformaldehyde (I) and trioxane (II), were used for this purpose. In systems I and II the effect of various D2O/CD3COOD ratios, at a constant DCl concentration, was studied, while for II the effect of changing DCl concentration was also investigated. The results show that in aqueous solution, formaldehyde exists primarily as the monomeric and linear oligomeric forms of methylene glycol. Reducing the amount of D2O (at constant DCl concentration), while increasing the CD3COOD content, results in an increase in the polymeric species and in trioxane. In addition, substitution of water by acetic acid results in systems that are catalytically more active than aqueous solutions of the same hydrochloric acid concentration. Along with the usual polymer-monomer equilibria which exist in such solutions, side reactions of methylene glycol with the hydrochloric acid present also occur to a small extent, e.g. acetylation, substitution of OH by Cl and the Cannizzaro reaction. It is suggested that these findings will result in a better understanding of the formaldehyde crosslinking reactions in cotton cellulose. 相似文献
902.
Conclusions The partial hydrolysis of the pectin ofPanax ginseng C. A. Mey gives a polygalacturonide which has a linear carbohydrate chain consisting of residues of D-galacturonic acid in the pyranose form linked by -(1 4)-bonds.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 4, pp. 201–203, 1969 相似文献
903.
Mechanism for polymerization of ε-caprolactam in the presence of both sodium and aluminum caprolactamate was investigated at 171°C. The role of Al(Cap)3 as an initiator was revealed. The apparent rate constant of propagation reaction decreased with the increase in the concentration of Al(Cap)3, as the two different metal salts interact even at 171°C. The activation energy of the overall polymerization reaction with this catalyst system was estimated to be 41.18 kcal/mole. 相似文献
904.
The percutaneous absorption of ketoprofen (KPF) from gel patches containing d-limonene and ethanol was investigated in rats. Plasma levels of KPF varied with the kind of polymers which constitute the gel patch, and the highest level was observed when the copolymer of ethylacrylate (EA) and diethyleneglycolmethacrylate (DEGMA) was used as a vehicle. The amount of KPF permeating through the rat skin from the gel patch was well correlated with that of ethanol. Permeations were enhanced with increase in the amount of d-limonene distributed from the vehicle to the skin tissue. The amount of d-limonene accumulated in the skin varied greatly with the kind of polymers; the highest accumulation was observed with the EA-DEGMA copolymer, and decreased with increasing affinity of d-limonene to the polymers. The reason EA-DEGMA copolymer showed the highest percutaneous absorption of KPF from gel patches containing d-limonene may be the hydrophilic nature of this polymer which showed the lowest affinity to d-limonene. 相似文献
905.
A. I. Nekhaev B. I. Kolobkov M. T. Toshev Kh. B. Dustov G. G. Aleksandrov 《Russian Chemical Bulletin》1991,40(4):827-830
Reaction of excess styrene with Fe3(CO)12 and sulfur (60°C, 15 h, Ar, S/Fe3(CO)12 0.6 g-atom/mole) gave Fe2(CO)6S2, Fe3(CO)9S2, Fe2(CO)6(S2CO), Fe2(CO)6S2(PhCHCH2), PhCHCH2S4, and a novel binuclear complex Fe2(CO)6(S2CH2S), whose structure was analyzed by x-ray crystallography. The crystals are monoclinic, a=7.764(3), b=13.205(4), c=6.628(6) Å, =98.97(3)°. V=671.2(7) Å3, Z=2, space group P21/m. The bond lengths are Fe-Fe 2.520(2), Fe-S 2.236(2), S-S 2.078(4), C-S 1.825(12), Fe-CO 1.784(8), and CO 1.148(9) Å.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 930–934, April, 1991. 相似文献
906.
Zusammenfassung Aus Fichten- und Buchen-Kunstfaserzellstoffen wurden -und -Cellulosen präparativ hergestellt und diese polymeranalog nitriert. Die entstandenen Nitrate wurden durch Behandeln mit Aceton in einen löslichen und unlöslichen Teil getrennt, die gewichtsmäßig bestimmt wurden. Die acetonlöslichen Nitratanteile wurden aus den Acetonlösungen durch steigende Wasserzusätze fraktioniert gefällt und die Fraktionen gewichtsmäßig bestimmt; weiters wurden die reduzierten Viskositäten der Fraktionen bestimmt. Während die Stickstoffgehalte der acetonlöslichen Nitratanteile etwa jenen von Cellulosenitraten entsprechen, betragen die Stickstoffwerte der acetonunlöslichen nur etwa die Hälfte bis ein Drittel davon. In den acetonlöslichen Anteilen liegen im wesentlichen Hexosane vor. Die höchsten Fraktionen der -Cellulosen enthalten Anteile bis annähernd etwa DP 200. Im Gegensatz dazu bestehen die acetonunlöslichen Nitratanteile von - und -Cellulosen hauptsächlich aus Mischungen von Nitraten von Pentosanen und Polyuronsäuren. Die Acetonlöslichkeit von Nitraten laugenlöslicher Anteile aus Kunstfaserzellstoffen gibt demnach orientierende Hinweise auf die chemische Zusammensetzung dieser Anteile.Herrn Prof. Dr.A. Wacek zum 60. Geburtstag gewidmet.Die vorliegenden Untersuchungen wurden bereits in den Jahren 1952 und 1953 durchgeführt. 相似文献
907.
V. V. Korshak S. V. Vinogradova V. A. Vasnev G. D. Markova T. V. Lecae 《Journal of polymer science. Part A, Polymer chemistry》1975,13(12):2741-2749
The effect of conditions of polycondensation on the structure of polymers formed from monomers with symmetric and asymmetric functional groups by nonequilibrium polycondensation has been studied for the system with acceptor-catalytic polyesterification of β-hydroxyethyl ethers of bisphenols and terephthalic acid chloride in the presence of triethylamine. Polymers with statistical or regular arrangement of diol residues in the chain can be produced in such systems, depending on the way in which starting compounds are introduced in the reactor. A difference in the reactivity of functional groups in an asymmetric monomer is not sufficient to produce polycondensation polymers with a regular structure. Gradual introduction of the symmetric monomer is essential to yield polymers with predominant “head-to-head” (“tail-to-tail”) configurations. Some properties of the resulting polymers have been studied. Polymers with ordered residues of the asymmetric monomers in the macromolecules have higher softening temperatures and an increased tendency for crystallization than the statistic polymers. 相似文献
908.
Abstract —Semi-empirical formulas for the ultraviolet erythema dose derived in an earlier paper are used to deduce an ultraviolet photoclimatology. We calculate the climatology of daily erythema radiation doses for the northern hemisphere at 5d? latitude intervals. Similar dose calculations are also performed specifically for ten metropolitan areas. Effects of seasonal and geographic variations of ozone, turbidity, and cloudiness on the local erythema doses are also investigated. We present a simple approximate analytic formula for the annual erythema dose as a function of latitude, cloud cover, and ground albedo for use in connection with studies of the epidemiology of skin cancer. The implications of possible ozone depletion due to a future fleet of supersonic aircraft in the stratosphere are discussed. These calculations are made for a normal ozone thickness of 0.32 cm and for a 5, 10, 20, and 50 per cent ozone reduction. 相似文献
909.
The compounds CdCr2S4 and CoCr2S4 have been hot pressed into disks that are highly transparent in the infrared. Stoichiometry has been altered by varying the ratio, where M2+ is Cd2+ or Co2+. The effects of nonstoichiometry on optical transmission were determined. Excess M2+ attenuates the transmission much more than excess Cr3+. 相似文献
910.
N. S. Prostakov V. G. Pleshakov T. Kholdarova V. P. Zvolinskii L. N. Plaksii 《Chemistry of Heterocyclic Compounds》1972,8(10):1264-1267
9-Methylnaphtho[2,1-b][1,6]naphthyrldine and 2,3-dimethyl-1-azaphenanthrene were obtained on a K-16 dehydrogenating catalyst from N-(1,2,5-trimethyl-4-piperidylidene)--naphthylamine, while N-cyclohexylidene--naphthylamine yielded N-phenyl--naphthylamine and benzo[a]carbazole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1400–1403, October, 1972. 相似文献