摘要:

AbstractThe kinetics of azocoupling between 1‐benzyl‐4‐phenyl‐, 1,3,4‐triphenyl‐, 4‐benzyl‐1‐methyl‐, 1,4‐dimethyl‐, 1,4‐diphenyl‐3‐methylmercapto‐ and 3‐benzyl‐mercapto‐1,4‐diphenyl‐1,2,4‐triazolium salts, and p‐N,N‐dimethylamino benzenediazonium tetrafluoroborate are studied spectroscopically in methanol/water 1:1 (v/v) at various pH values following up the growing‐in of the respective azodyes.The competing reactions of the diazonium salt with the solvent and the buffer (NH3/NH4Cl), and of some bleaching of the azodye formed were studied separately and accounted for in the kinetic treatment.From the pH dependence of the coupling rate constants and by application of kinetic models it turned out that not the widely accepted one‐step deprotonation mechanism of the quaternary triazolium salts applied but a two‐step mechanism comprising of pseudobase formation and their subsequent deprotonation is valid.Using the pertinent kinetic model the pK values of pseudo‐base formation (pKR+) and their depro

ISSN:0021-8383    

DOI:10.1002/prac.19913330102

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

AbstractThe reaction of 3H,6H‐1,2‐dithiolo[4,3‐c]1,2‐dithiole‐3, 6‐dithione (1) with primary aliphatic amines (8a,b) gives 3H,6H‐3,6‐bisalkylimino‐1,2‐dithiolo[4,3‐c]1,2‐ dithiole (9a,b), 3H,3‐N‐alkylamino‐5‐N‐alkylthiocarbamido‐1, 2‐dithiolium‐4‐thiolate (10a,b) and 3H,3‐N‐alkylimino‐4‐alkylamino‐5‐N‐alkylthiocarbamido‐1,2‐dithiole (11a,b). The compounds9‐11can be formed from one another. The compounds10a,breact with nickel chloride to the stable complexes14a,b. In basic medium10gives the salt of 3H,3N‐alkylthiocarbamido‐1,2‐dithiole‐4‐thiolate15, which reacts with methyl iodide

ISSN:0021-8383    

DOI:10.1002/prac.19913330103

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

1H‐ and13C‐N.M.R. Spectroscopic Investigations of Substituted 1, 1‐Dioxo‐1, 2‐thiazines; Additivity of the Substituent Effects.The influence of various XCH2substituents (X: Cl, Br, I, SCN, SO2CH3, SC(NH2)2⊕, Py⊕) in the 3‐, 5‐ and 3, 5‐position of the 1, 1‐dioxo‐2‐phenyl‐1, 2‐thiazine on the1H‐ and13C‐n.m.r. chemical shifts of the ring atoms is described. The substituent effects are additive. The1H‐ and13C‐n.m.r. chemical shifts of the 3, 5‐substituted 1, 1‐dioxo‐1, 2‐thiazines can be calculated from increments d

ISSN:0021-8383    

DOI:10.1002/prac.19913330104

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

CLAISEN‐Condensations with Selected Dithioesters ‐ Synthesis of Special 3‐Methylthio‐acrylnitriles.A useful synthetic route to the mono‐ and diheteroaryl‐3‐methylthio‐acrylnitriles1and2is demonstrated by the thioanalogous CLAISEN‐condensation.In the presence of sodium hydride in tetrahydrofurane or under PTC‐conditions heteroaryl dithiocarboxylic esters3react with CH‐acidic compounds4or9to form 3‐mercapto‐acrylnitriles (e. g.5). Methylation leads to mono‐ and diheteroaryl‐3‐methylthioacrylnitriles1and10(type2). In the same manner tetrathioterephthalic ester6reacts with two equivalents of CH‐acidic compounds yielding8and11. By means of spectroscopic methods, especially1H‐ and13C‐n.m.r., the structures of

ISSN:0021-8383    

DOI:10.1002/prac.19913330105

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

AbstractA simple, Large‐scale preparation of mammalian gonadoliberin was elaborated using classical solution methods without protecting side‐chain functions. At the final stage, a hexapeptide segment was condensed with the corresponding tetrapeptide and the obtained decapeptide was purified by a single chromatographic procedure on silica gel. The total efficiency of the whole synthesis and the purity of the product amounted to 34% and 98.3%, respectiv

ISSN:0021-8383    

DOI:10.1002/prac.19913330106

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

ISSN:0021-8383    

DOI:10.1002/prac.19913330107

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

ISSN:0021-8383    

DOI:10.1002/prac.19913330108

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

AbstractSurface excess isothermers were determined and interpreted for systems containing 2‐hydroxy‐5‐t‐nonylbenzaldehyde oxime (1), 2‐hydroxy‐5‐t‐octylacetophenone oxime (2) and 2‐hydroxy‐5‐t‐octylbenzophenone oxime (3). These surface excess isotherms were used to predict reaction orders with respect to hydroxyoximes for various versions of interfacial process. Agreement with the experimental data was observed both for the interfacial and bulk aqueous mechanism. The surface activity of extractants cannot be recognized as the sole evidence for the interfacial mechanism of extraction. More experimental kinetic data are needed in order to determine the effect of hydroxyoxime concentration upon the reaction order. According to the interfacial mechanism, with the formation of the stable 2:1 complex as the limiting step the reaction order in hydroxyoxime equal to 1 is observed over a large range of hydroxyoxime concentration, but increases to 1.5‐2.0 fo

ISSN:0021-8383    

DOI:10.1002/prac.19913330109

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

AbstractMethylhydrazones (III) of aromatic aldehydes and ketones react with nitrile imines (II) to give 1,2,3,4‐tetrahydro‐s‐tetrazinesIV(1‐9) which exhibits “ring‐chain” tautomerism in solution. The extent of this tautomerism is dependent both on steric and electronic effects of substituent groups at C‐3 and C

ISSN:0021-8383    

DOI:10.1002/prac.19913330110

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

ISSN:0021-8383    

DOI:10.1002/prac.19913330111

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY