摘要:

AbstractA relation between the limiting viscosity number [η] and the weight average molecular weight of polyethyleneimine (PEI) is proposed. Special care was taken to suppress the marked polyelectrolytic character of PEI in water for both viscometric and light‐scattering measurements. For these measurements various fractions were isolated in three different ways from some commercially available PEI′s, all having broad molecular weight distributions. To obtain an impression of the molecular weight distribution of the resulting fractions, some osmotic measurements to obtain the number average molecular weight and some ultra‐centrifuge runs were per

ISSN:0165-0513    

DOI:10.1002/recl.19730920102

出版商:WILEY‐VCH Verlag    

年代:1973

数据来源: WILEY

摘要:

AbstractSeveral tetra‐alkoxyethenes have been synthesized from dialkoxy‐monoaryl‐oxymethanes by treatment with sodium hydride. The occurrence of dialkoxy carbenes as possible reaction intermediates is discussed. Best results (45‐60%) were obtained with dialkoxy‐mono‐p‐chlorophenoxymethanes.Tetra‐aryloxyethenes have been prepared by a similar procedure in which diaryloxymethyl chlorides were used as sta

ISSN:0165-0513    

DOI:10.1002/recl.19730920103

出版商:WILEY‐VCH Verlag    

年代:1973

数据来源: WILEY

摘要:

AbstractTwo routes are described for the synthesis of 1,3‐benzo[e]thiazepines, a novel class of heterocyclic compounds. The first route is a reaction between 2‐bromo‐methylbenzyl or 2‐bromomethylbenzoyl bromide and a thioamide or a thiourea. In an analogous reaction a 1,3‐thiazepine can be synthesized from 4‐bromobutyryl chloride andN,N′‐diphenylthiourea. The second route comprises cyclization ofN′‐(2‐bromomethylbenzoyl)‐N′‐disubstituted thioureas. Rather unexpectedly, the correspondingN′‐monosubstituted compounds yielded benzo[c]pyrrolidine derivatives. Pyrrolidines were observed from the cyclization ofN′‐(4‐bromobutyryl)‐N′‐mono/disubstituted thioureas.The reaction mechanisms and the spectroscopic data of the reaction products are discussed.The 1,3‐benzo[e]thiazepines were converted into the correspond

ISSN:0165-0513    

DOI:10.1002/recl.19730920104

出版商:WILEY‐VCH Verlag    

年代:1973

数据来源: WILEY

摘要:

AbstractWhen treated with alkali metals in liquid ammonia at −70° cycloheptatriene adopts two electrons and a proton yielding the cycloheptadienyl anion. Protonation of this anion yields 1,3‐ and 1,4‐cycloheptadiene in a ratio which depends rather strongly on the proton donor used. Decreasing acid strength of the proton donor favours 1,3‐cycloheptadiene formation. The selectivity of protonation also depends on the alkali metal used and on the concentration. At −33° ammonia protonates the cycloheptadienyl anion yielding 1,3‐cycloheptadiene. This enables one step reduction of cycloheptatriene to cycloheptene. Reduction of 7‐deuterocycloheptatriene shows the first proton addition to cycloheptatriene to be irreversible.Alkylation of the cycloheptadienyl anion yields mixtures of 3‐alkyl‐1,4‐cycloheptadiene and 5‐alkyl‐1,3‐cycloheptadiene in which the former compo

ISSN:0165-0513    

DOI:10.1002/recl.19730920105

出版商:WILEY‐VCH Verlag    

年代:1973

数据来源: WILEY

摘要:

AbstractAntimony pentafluoride is a unique reagent for the formation of stable carbonium ions by oxidation of saturated hydrocarbons. The kinetic parameters for the abstraction of hydride ion from ethane and neopentane have been determined. Compared to the reactions with mixedBrönsted‐Lewisacid systems (HF‐SbF5, molar ratio ⩾5/1, and FSO3H‐SbF5, molar ratio 1/1), the analogous reactions with pure SbF5show considerably enhanced reaction rates. Moreover, neat SbF5is capable of removing the aldehydic proton from aldehydes to yield oxocarbonium ions. It is concluded that for hydride abstraction in the so‐called “magic acid” (FSO3H‐SbF5, molar ratio 1/1) a mechanism involving protonation to alkanonium ions is not the main

ISSN:0165-0513    

DOI:10.1002/recl.19730920106

出版商:WILEY‐VCH Verlag    

年代:1973

数据来源: WILEY

摘要:

AbstractThe rate of the conversion of benzene into biphenyl (“tank flow” reactor, atmospheric pressure, nitrogen dilution, 540°) is found to be highly dependent on type and concentration of additives. For example, small amounts of sulfur or oxygen lead to strong retardation, but a little formaldehyde or C2Cl6has a profound accelerating effect. Wall (memory) effects are also observed.These facts point to a radical chain mechanism ‐ involving H· and phenyl radicals ‐ rather than to a (bi)molecular process as was recently proposed byFieldsandMeyerson. Other phenomena (H/D exchange, oxidation to phenol) are also consonant with a (semi)quantitative description based on thermo‐chemical kinetics.The thermolysis of other arenes can be explained analogously; thus, biphenyl (giving benzene, ter‐ and quater‐phenyls) forms H·, C6H5‐C6H4· and phenyl radicals as intermediates, the latter fragments arising through H· + biphenyl → (C6H6‐

ISSN:0165-0513    

DOI:10.1002/recl.19730920107

出版商:WILEY‐VCH Verlag    

年代:1973

数据来源: WILEY

摘要:

AbstractUrea, thiourea and someN′‐alkyl(di)substituted ureas and thioureas were found to react as the amine component in Mannich‐type condensation reactions withp‐toluene‐ or phenylmethane‐sulfinic acid and aldehydes. Mono‐ or di‐alkylation products are formed in good yields depending on theN′‐ andN′‐substituents in the substrate, whileN,N,N′‐trimethylurea or ‐thiourea failed to react.N′‐Hydroxy‐N′‐phenylthiourea is alkylated on theN′‐atom bearing the OH‐substituent as demonstrated by the ESR spectrum of the thioacyl nitroxide derived from the condensation product. Thiobenzamide, in contrast with thioacetamide, also condensed withp‐toluenesulfinic acid and formaldehyde orN′‐butyraldehyde. With benzaldehyde, however, Mannich‐type condensation did not occur and 3,5‐diphenyl‐1,2,4‐thiadiazole was isolated instead.The NMR spectra of several urea and thiourea condensation products provided evidence for hindered internal rotation in the urea and thiourea function and some ΔG≠values for the exchange process were estimated. Intramolecular shielding effects were observed in the NMR spectrum

ISSN:0165-0513    

DOI:10.1002/recl.19730920108

出版商:WILEY‐VCH Verlag    

年代:1973

数据来源: WILEY

摘要:

AbstractNi(C2H5OH) (t‐C4H9NC)Cl2and nickel acetylacetonate are effective catalysts for the polymerization of isocyanides. Protic solvents and the presence of an acid accelerate the polymerization in case of nickel acetylacetonate. The reaction products are characterized as poly‐Schiff bases. Upon treatment with acid the polymers of primary alkyl isocyanides rearrange to polycyani

ISSN:0165-0513    

DOI:10.1002/recl.19730920109

出版商:WILEY‐VCH Verlag    

年代:1973

数据来源: WILEY

摘要:

AbstractLeu‐Ser‐Phe‐Met‐Ala‐Ile‐Pro‐Pro‐Lys‐Lys and 14 smaller peptide fragments simulating increasing parts of the sequence around the rennin sensitive Phe‐Met bond in k‐casein have been synthesi

ISSN:0165-0513    

DOI:10.1002/recl.19730920110

出版商:WILEY‐VCH Verlag    

年代:1973

数据来源: WILEY

摘要:

Abstract(E)‐(2S)‐2‐Amino‐4‐methylthio‐3‐butenoic acid (1; “dehydro‐L‐methionine”) was prepared through reaction stages 2‐7 using β‐acetamido‐β, β‐di(ethoxycarbonyl)prop

ISSN:0165-0513    

DOI:10.1002/recl.19730920111

出版商:WILEY‐VCH Verlag    

年代:1973

数据来源: WILEY