摘要:

Abstract3,17‐Dioxo‐Δ4‐androsten‐19‐al (II) is a suitable starting material for the preparation of estrane derivatives.Autoxidation gives the corresponding 10β‐hydroperoxide III, which can be converted to estrone (V) by reduction and aromatization.Treatment with alkaline reagents under various conditions can produce 3‐oxo‐Δ4‐ (VI), 3‐oxo‐Δ5(10)‐ (VII) and 2‐hydroxymethylene‐3‐oxo

ISSN:0165-0513    

DOI:10.1002/recl.19700890502

出版商:WILEY‐VCH Verlag    

年代:1970

数据来源: WILEY

摘要:

AbstractThe activity for the hydrogenation of benzene has been studied for supported platinum, palladium and nickel as a function of metal particle size and carrier. Metal crystallite sizes varied between 10 and 400 Å and silica, alumina, silica‐alumina and silica‐magnesia were used as supports. It has been found that the activity per exposed metal atom is independent of the metal crystallite size or of the support used. The hydrogenation activities per exposed metal atom at a temperature of 100°C and a hydrogen pressure of 5.6 atm are ranked as follows:kpt: kNi: kPd= 18:7:1.It is further shown that the activation energies observed experimentally for the various catalysts at a given set of conditions are predicted with a high degree of accuracy with the aid of the theory of absolute reaction rates, based on a resonable estimate of the number of exposed metal atoms per hydrogenation

ISSN:0165-0513    

DOI:10.1002/recl.19700890503

出版商:WILEY‐VCH Verlag    

年代:1970

数据来源: WILEY

摘要:

AbstractThe oxidation of benzaldehyde to benzoic acid with V2O5, SnO2‐promoted V2O5and MnO2as catalysts has been investigated. The reaction mechanism includes the following steps: dissociative chemisorption of benzaldehyde, yielding an asymmetric covalent benzoate complex with one oxygen atom of the sufrace, atomic rearrangement to the symmetric benzoate ion, desorption of benzoic acid and reoxidation of the catalyst surface by adsorption of oxygen. The activity of the oxides is found to be related to their ability to release oxygen. An antibatic relation between the Gibbs free energy of oxygen release and the catalytic activity is demonstrated. The action of the tin promoter in the mixed oxide catalyst is due to the loosening of the metal‐oxygen bond. A parallelism is suggested between the catalytic selectivity and the differential increase of the enthalpy of oxygen release with increasing degree of reduct

ISSN:0165-0513    

DOI:10.1002/recl.19700890504

出版商:WILEY‐VCH Verlag    

年代:1970

数据来源: WILEY

摘要:

AbstractThe reaction kinetics of the catalytic vapour‐phase hydrogenation of cyclohexene on evaporated nickel films has been studied in a temperature range from − 20 to − 45° in a flow system. To this end, an apparatus has been constructed in which hydrogen and cyclohexene partial pressures, flow‐rate and reaction temperature could be varied independently.In the range studied, the reaction has been found to be zero‐order with respect to the cyclohexene and roughly half‐order in regard to the hydrogen partial pressure, indicating that the formation of chemisorbed C6H11groups is the slow step in the reaction. The measured rate was compared with that calculated from the absolute

ISSN:0165-0513    

DOI:10.1002/recl.19700890505

出版商:WILEY‐VCH Verlag    

年代:1970

数据来源: WILEY

摘要:

AbstractThe homogeneous hydrogenation of a series of substitutedtrans‐cinnamic acids with pentacyanocobaltate(II)‐ion has been investigated. The reactions were found to be first order in pentacyanohydridocobaltate(III) as well as in substrate, and zero order in cyanide. Electronic substituent effects may be expressed in terms of aHammett‐Yukawarelationship with ρ = 0.67. In the hydrogenation ofcis‐cinnamic acid partial isomerization to thetrans‐isomer was observed. The deuteration ofcis‐ andtrans‐cinnamic acid and the hydrogenation of α,β‐dideutero‐cis‐cinnamic acid have been studied. The results can be understood by considering the reaction as a stepwise hydrogen atom transfer from the hy

ISSN:0165-0513    

DOI:10.1002/recl.19700890506

出版商:WILEY‐VCH Verlag    

年代:1970

数据来源: WILEY

摘要:

AbstractAmmonia production from cyanate was measured as a function of pH.The kinetic description of the process included acid‐catalyzed hydrolysis of isocyanic acid and spontaneous hydrolysis of isocyanic acid and cyanate. These reactions were predominant at pH values below 2, between 3 and 8, and above 9, respectively.The hydrolysis was strongly catalyzed by certain bivalent anions. The geometry of the anion appeared to be an important factor in the catalytic process, since carbonate, phosphate, succinate, maleate, citrate and phthalate were catalysts, whereas other bivalent anions,viz.sulfate, oxalate, fumarate and isophthalate, were without effect. Catalysis by bivalent anions was supposed to proceedviacarbamoyl derivatives of the anions. The negatively charged group of the carbamoyl derivative was thought to cause an intramolecular general base‐catalyzed reaction.The implications of this study for the mechanism of urease action were conside

ISSN:0165-0513    

DOI:10.1002/recl.19700890507

出版商:WILEY‐VCH Verlag    

年代:1970

数据来源: WILEY

摘要:

AbstractThe mass spectra of twenty‐six β‐ and α,β‐substituted butenolides have been examined. Fragmentation of the butenolide ring can be rationalised on the basis of the fragmentation pathways described for β‐hydroxybutenolides. However, a number of butenolides,e.g.the α‐(substituted)benzamido‐β‐hydroxymethyl‐butenolides, show a weak fragmentation of the ring. The fragmentations in which the substituents are involved are more favourable and interactions between the substituents on the α‐ and β‐positio

ISSN:0165-0513    

DOI:10.1002/recl.19700890508

出版商:WILEY‐VCH Verlag    

年代:1970

数据来源: WILEY

摘要:

Abstract1‐t‐Butylcyclohexanecarboxylic acid (1) has been synthesized fromt‐butyl‐cyclohexanols as well as from 2‐(1‐methylcyclohexyl)‐2‐propanol by theKoch ‐Haafcarboxylation. A side product in these preparations is 2‐methyl‐2‐(1‐methylcyclohexyl)propionic acid (5).Details are given for the preparation of thecis‐ andtrans‐isomers of 2‐, 3‐and 4‐t‐butylcyclohexanecarboxylic acid (cis‐ andtrans‐2, 3and4) starting from the correspondingt‐butylbenzoic acids.Thet‐butylbenzoic acids and their methyl esters have been hydrogenated over transition metal catalysts at 25°. Palladium differs from platinum, rhodium and ruthenium by, in all cases, giving in excess the most stable isomer. In the hydrogenation of 2‐t‐butylbenzoic acid over rhodium desorbed 6‐t‐butyl‐1‐cyclohexene‐1‐carboxylic acid is shown to be the main source of thetrans‐2formed.The mass spectra of1−4are presented and discussed. The mode of fragmentation ofcis‐4andcis‐3was f

ISSN:0165-0513    

DOI:10.1002/recl.19700890509

出版商:WILEY‐VCH Verlag    

年代:1970

数据来源: WILEY

摘要:

AbstractThe reaction of bromine with a variety of dimethyl acetals at − 60° in sulfur dioxide is described. Electrophilic attack of bromine on oxygen leads to methyl hypobromite (CH3OBr) together withmonomethoxycarbenium bromide or ‐ depending on the stability of the cation ‐ its covalent counterpart, the α‐bromo‐ether. The reaction is catalysed by acids. Acetals derived from linear and cyclic carbonyl compounds react in this way with one exception: with 1,1‐dimethoxycyclopropane, the acetal of cyclopropanone, electrophilic attack by bromine is not on oxygen, but on the cyclopropane ring. Ring rupture leads to a relatively stabledimethoxy

ISSN:0165-0513    

DOI:10.1002/recl.19700890510

出版商:WILEY‐VCH Verlag    

年代:1970

数据来源: WILEY

摘要:

AbstractFour spiro[cyclopentabithiophene]fluorenes have been synthesized. A distinct bathochromic shift due to spiroconjugation is found in their UV spectra, as predicted bySimmonsH. E. SimmonsandT. Fukunaga, J. Am. Chem. Soc.89, 5208 (1967)..

ISSN:0165-0513    

DOI:10.1002/recl.19700890511

出版商:WILEY‐VCH Verlag    

年代:1970

数据来源: WILEY