摘要:

AbstractAromatic aldehydes5and α‐keto acids8in the presence of cyanide ion, which usually give the benzoin condensation products, were converted oxidatively to the corresponding benzoic acids10by the catalytic action of the title flavin. The change in the reaction route cannot be achieved completely by flavin1. Product analyses and kinetic measurements established that the carbanion intermediate,\documentclass{article}\pagestyle{empty}\begin{document}${\rm R}\hbox{---} \mathop {\rm C}\limits^ \ominus \left( {{\rm OH}} \right)\left( {{\rm CH}} \right)$\end{document}, which is formed through rate‐limiting deprotonation or decarboxylation of the cyanide‐adducts, is oxidized immediately by the title flavin. The influence of polymer structure on the efficiency of flavin trapping is dis

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810901

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractPoly(oxydodecandioyloxy‐1,4‐phenylene‐2‐methylvinylene‐1,4‐phenylene) (1) was synthesized and partially characterized by differential scanning calorimetry and X‐ray diffraction methods. The polymer shows a thermotropic liquid crystalline behavior. The X‐ray diffraction spectrum of the anisotropic liquid is coherent with a nematic phase. Solid state polymorphism i

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810902

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThe polymerization of octanelactame (1) initiated by HCl takes place according to the characteristic kinetic curves. Both characteristics, i.e., the fast initial and the extremely slow further stages, and the kinetic anomaly (in certain cases under otherwise identical conditions less polymer is formed at higher than at lower temperatures) can be interpreted easily on the basis of a mechanism already suggested by the authors. The two relevant chain growth reactions, i.e., lactam addition on\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}\mathop {\rm N}\limits^ \oplus {\rm H}_{\rm 3} $\end{document}‐groups and the reaction between\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}\mathop {\rm N}\limits^ \oplus {\rm H}_{\rm 3} $\end{document}andN‐acylamide groups, proceed through a tetrahedral intermediate in two directions, one of them being the known chain growth, the other one an amidine (or acylamidine) formation, in which the active groups, ensuring chain growth, desactivate. Both kinetic characteristics could be interpreted on the basis of the suggested mechanism, by measuring the amounts of amino and amidine groups with the progress of polymerizat

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810903

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThe chemical structure of polybutadienyllithium/TiCl4complexes was studied for several values ofr= [Li]/[Ti], using spectroscopic methods, gravimetry, and the elemental analysis. Dependent on the molecular weight of the polybutadienyl chain, the complexes are soluble or insoluble in hexane. The soluble systems were used for the initiation of the polymerization of ethylene, leading to a mixture of homopolybutadiene and block copolymers, slightly reticulated. The efficacity of such systems can be estimated to be 0,8.

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810904

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractVariously composed copolymers from styrene and 4‐vinylpyridine (4‐VP) were prepared and their complex formation reactions with benzylbis(dimethylglyoximato)Co(III) [BzCo(III)(DMG)2] andN,N′‐ethylenebis(salicylideneiminato)Co(II) (Co(II)salen) were studied kinetically by the stopped‐flow rapid scanning spectroscopy. For the complex formation reaction with BzCo(III)(DMG)2, the relationship between the complex formation constantKand the content of 4‐pyridylethylene units in the copolymers showed an unusual bell‐type curve, and theKvalues were higher than theKvalue of complexation with pyridine. From the correlation betweenK, k(complex formation rate constant), andk′ (complex dissociation rate constant), it resulted that (1) the higherKvalues of the polymer systems are due to the lowerk′ values compared with the pyridine system, and (2) the bell‐type change of theKvalues is also caused by thek′ values. In the case of Co(II)salen‐copolymer systems, two species of the complex, i.e., mono‐ and diaxial coordinated complexes were clearly identified by spectrometric kinetics, whereas the pyridine system gave only a mono‐axial coordinated complex. The diaxial coordination seems to lead to a much more favorable structure than the monoaxial one, due to the entropic gain or to

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810905

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThe photo‐oxidation of solid polymers at ambient temperatures is shown to be greatly affected by the low mobility of radicals in the solid state. When a radical pair, produced by photo‐initiation, escapes the initial polymer cage, the probability of its recombination remains high even after several propagation steps. This phenomenon, known as secondary cage recombination, has a pronounced effect on the kinetics of oxidation and on the mechanism of photostabilisation by radical scavengers. The occurrence of secondary cage recombination is demonstrated for polypropylene photo‐oxidation and a kinetic analysis is developed to predict the consequences of this e

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810906

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractThis investigation deals with metathesis degradation products of modified 1,4‐polybutadiene (poly(1‐butenylene)) which have not been taken into consideration as yet, e.g. substituted cyclopentene and linear isomerization products. Substituents were introduced into 1,4‐poly‐butadiene either by partial bromination withN‐bromosuccinimide followed by a Grignard‐Wurtz reaction or by reaction with the corresponding methyl compound and dicumyl peroxide. Polymers with 2‐methylbenzyl, 4‐methylbenzyl, 4‐chlorobenzyl, 4‐methoxybenzyl, 2‐naphthylmethyl, 2,4,6‐trimethylphenyl, 1‐naphthyl, 9‐anthryl, and 9‐phenanthryl substituents were degraded by metathesis with 4‐octene using WCl6/(CH3)4Sn as a catalyst and were analyzed by gas chromatography/mass spectromet

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810907

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractPolyurethanes containingD‐cellobiose residues in the main chain were synthesized fromD‐cellobiose and diisocyanates. The direct addition polymerization without blocking the excess hydroxy groups afforded soluble polyurethanes with inherent viscosities up to 1,08 dl · g−1. The pendant hydroxy groups in these polyurethanes were utilized for polymer reactions such as acetylation and crosslinking. Water absorption values of polyurethane films were confirmed to be very high. Acetylation decreased the values drastically, although the degrees of acetylation were not high. Thermal stability and crystallinity were also s

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810908

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractPolyvinylpyrrolidone forms complexes with hydrogen halides (HX; X = Cl, Br, I) and halogen molecules (Y2; Y = Br, I). For these compounds a structure is proposed in which the proton is coordinated to the carbonyl groups of two pyrrolidone rings by strong hydrogen bonds. The\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm XY}_{\rm 2}^ \ominus $\end{document}‐anion is attached ionically to this complex cation. The structure of these complexes could be elucidated by comparative examination of the Lig2· HX · Y2‐complexes of model compounds such asN,N‐dimethylacetamide,N‐alkyl‐2‐pyrrolidones (2a–d), and 1,3‐bis(2‐oxo‐1‐pyrrolidinyl)butane (3) and the analogous polyvinylpyrrolidone complexes. The structure of the (N‐methyl‐pyrrolidone)2· HI3‐complex was examined by X‐ray structure analysis. In a similar way the potassium salts (Lig2· KX · Y2) of the complex acids could be prepared from the ligands, potassium halides, and halogen molecules. Unlike the proton, the potassium cation appears to be only weakly attached to

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810909

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractHydrolyses ofp‐nitrophenyl acetate (PNPA) and 3‐acetoxy‐N,N,N‐trimethylanilinium iodide (ANTI) catalyzed by poly[p‐vinyl(thiophenol)‐co‐acrylic acid] (PSH) were studied in the pH range of 8 – 9,5. The reaction of PNPA followed pseudo‐first‐order kinetics and was found to be catalyzed by the thiophenolate ions on the polymer backbone. In the case of positively charged ANTI, the rate of catalysis showed substrate saturation phenomena and could be described by a Michaelis‐Menten kinetics. This indicates that this reaction proceeds via a complex formed by electrostatic interaction between the substrate and the negatively charged polymer catalyst. When ionic strength was increased to 0,12 mol/l the reaction did not further follow the Michaelis‐Menten kinetics, suggesting that the complexation constant or the reaction rate of the complex might vary with the amount of the substrate incorporated in the polymer domain. Positively chargedN,N,N‐trimethylanilinium iodide competively inhibited the PSH‐c

ISSN:0025-116X    

DOI:10.1002/macp.1980.021810910

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY