ISSN:0165-0513    

DOI:10.1002/recl.19610800502

出版商:WILEY‐VCH Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractThe theory described in part I of this seriesJ. H. Sluyters, Rec. trav. chim.79, 1092 (1960).is applied to alternating current polarography by treating the complex cell impedance and cell admittance as functions of d.c. voltage.It is proposed to plot a.c. polarograms in the complex impedance or admittance plane. By this method it is possible to reduce the uncertainty in the height of the peak caused by the base current. An exactly linear relationship between the quantity measured and concentration can be obtained over a large range of concentrations by means of a simple construction.The measurements can be performed over a wide range of frequencies. Consequently, in some cases, a higher sensitivity can be obtained, because the most favourable frequency can be chosen.The method is not only suitable for analytical purposes, but also for the determination of the fundamental constants of electrode processes (rate constants, diffusion constants and double layer capacities).

ISSN:0165-0513    

DOI:10.1002/recl.19610800503

出版商:WILEY‐VCH Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractA method is described for determining adsorption isotherms of gases on solids under elevated pressures. Results are given for nitrogen as adsorbate and alumina as adsorbent. The range covered extends to 3000 atm at temperatures between ‐ 7.6° and 100°.The volume in which the experimentally determined equation of state is valid is defined as the total volumevminus a volumev0of the adsorbent sample inaccessible to the gas as determined with helium at low pressures.A quantity ΔGis taken as a measure of the amount of gas adsorbed. It is defined as the difference between the total amount of gas exposed to the adsorbent and the quantity which would be present in the volumev‐v0at the experimental temperature and pressure if no adsorption occurred.With increase of pressure ΔGincreases till a gas density ρg of about 175 amagat is reached, then it falls off (practically linearly with ρg), but rises again steeply at densities above 500 amagat. No hysteresis has been found; the alumina showed no permanent change after completion of the experiments.In the first and second range δΔG/δTis negative but in the third section it changes sign. Apparently the adsorption then changes from an exothermic to an endothermic process. An attempt is made to interpret the linear section in terms of a simple two

ISSN:0165-0513    

DOI:10.1002/recl.19610800504

出版商:WILEY‐VCH Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractThe following three phase equilibria (dependence of pressure on temperature) have been determined in order to find out which compounds occur in the above mentioned system:From these measurements it follows that in all probability NbOCl3is the only compound occurring in this binary system.An analytical method has been worked out for the determination of NbCl5in the presence of NbOCl3.By extrapolation from the binary‐melt‐diagram, the melting point of NbCl5is found to be 206.8° ±

ISSN:0165-0513    

DOI:10.1002/recl.19610800505

出版商:WILEY‐VCH Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractThe commonly accepted structure of γ‐coniceine, the major alkaloid ofConium maculatumL., is revised on the basis of results obtained in the present study with “active hydrogen” determinations and with regard to nuclear magnetic resonance spectra. Infra‐red spectra also support this revision.γ‐Coniceine is 2‐n‐propyl‐3,4,5,6‐tetrahydropyridine.The revised structure of γ‐coniceine (a Δ1‐ piperideine) seems of interest with a view to the biogenesis of the piperidine alkaloid

ISSN:0165-0513    

DOI:10.1002/recl.19610800506

出版商:WILEY‐VCH Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractThe gas‐phase chlorination of phenoxybenzene was studied at 300‐500°, using the experimental methods described earlier. The results obtained are in contrast with those found in liquid‐phase chlorination: there the product was mainly para‐chlorophenoxybenzene, while in the present investigation, at temperatures above 350°, monochlorinated products were mainly the meta‐isomer; they did not contain any ortho‐compound. Instead, dibenzofuran was formed.Between 300 and 350°, appreciable proportions of para‐chlorophenoxybenzene were also formed, presumably owing to the occurrence of electrophilic substitution in the liquid‐phase afterchlorination or at the walls of the reactor.The high‐temperature halogenation of phenoxybenzene therefore leads to substitution at the carbon atom carrying the highestpositivecharge, i.e. the position corresponding to the highest Hammett σ‐value, in the same way as in our earlier gas‐phase halogenations of haloben

ISSN:0165-0513    

DOI:10.1002/recl.19610800507

出版商:WILEY‐VCH Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractToluene‐14C1produced by the thermal neutron irradiation of a mixture of benzene and 2‐methylpyrazine is not specifically labelled in the methyl group, ruling out simple hydrogen replacement in benzene by the recoiling carbon‐14 for at least some fraction of the radioactive toluene produced. Using a recently published degradation scheme, the distribution of radioactivity in the ring relative to the methyl group has now also been deter

ISSN:0165-0513    

DOI:10.1002/recl.19610800508

出版商:WILEY‐VCH Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractA series of chlorinations of benzene derivatives C6H5X showed that three main reaction types may be distinguished, viz. a) substitutions into the nucleus with retention of X (X = C6H5‐O, Cl, F, CN, CCl3, COCl, COOCH3), b) substitution within the group X (X = alkyl, CHO, probably OCH3) and c) exchange of X for Cl (X = NO2, CHO, Br, probably Cl).Bromination of chlorobenzene led to bromobenzene and bromochlorobenzenes as well as to dibromobenzenes and dichlorobenzenes. Isomer distributions in the latter two dihalides were slightly different from those found in the bromination of bromobenzene and chlorination of chlorobenzene, respectively.Some of the mechanisms involved are briefly discusse

ISSN:0165-0513    

DOI:10.1002/recl.19610800509

出版商:WILEY‐VCH Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractDie vorliegende Arbeit beschreibt die Synthesen von 2‐Propyl‐1‐desaza‐adenin und von 2‐Propyl‐3‐desaza‐adenin, nach Analogie der Synthesen von in der 1. und 3. Mitteilung dieser Reihe beschriebenen Strukturanal

ISSN:0165-0513    

DOI:10.1002/recl.19610800510

出版商:WILEY‐VCH Verlag    

年代:1961

数据来源: WILEY

摘要:

AbstractA convenient preparation is described ofDL‐4‐allohydroxyproline by reduction ofDL‐4‐oxoproline with sodium borohydride in aqueous methanol. This reduction proceeds without appreciable formation of DL‐hydroxyproline, as shown by paper chromatography and by paper electrophoresis. The allo‐configuration of the reduction product (OH/COOH incis‐position) was proved further by conversion of the latter into its lactone

ISSN:0165-0513    

DOI:10.1002/recl.19610800511

出版商:WILEY‐VCH Verlag    

年代:1961

数据来源: WILEY