摘要:

AbstractVapours of benzene and derivatives such as chlorobenzene are thermally unstable aboveca.500°C in both nitrogen and hydrogen atmospheres. Major products range from biaryls at lower temperatures to carbon black at temperatures above 1000°C. In hydrogen, dechlorination (ArCl → ArH) is a prominent reaction of (poly)chlorinated benzenes.In hydrogen, between 500‐1000°C, τ ∼ 5‐10 s, biaryl formation is accompanied by production of comparable amounts of methane. This reaction, for the major part, is shown not to be due to hydrogenolysis of carbonaceous deposits or of the small quantities of ethane/ethene which are also formed.A mechanistic rationale is presented based on isomerization of cyclohexadienyl radicals (formed in equilibrium with arene and•H), ultimately leading to•CH3as the precu

ISSN:0165-0513    

DOI:10.1002/recl.19841031001

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThe impedance of poly(pyrrole) (PP) and poly(N‐methylpyrrole) (PMP) films on platinum in an acetonitrile, LiClO4solution has been measured. At potentials more positive than a characteristic value, the electrodes exhibit porous behaviour and the impedance is determined by the double‐layer capacitance and the solution resistance inside the pores. At more negative potentials, the PP and PMP electrodes behave like flat‐plate electrodes and two impedance contributions can be distinguished,i.e.a material contribution (material resistance and material capacitance) and a contribution from the interphase polymer‐electrolyte (faradaic resistance and double‐layer cap

ISSN:0165-0513    

DOI:10.1002/recl.19841031002

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThermolysis oftert‐butyl hydroperoxide (1) in nitrogen with an excess of benzene in the temperature range 200‐300°C, leads to biphenyl (2) as the only observable benzene‐derived product. With chlorobenzene, dichlorobiphenyls (4) are formed, together with chlorobiphenyl (5),ca.12% on4, and phenol (20‐25% on4); chlorophenols are not produced. The use ofca.equimolar quantities of iodine based on1results in formation of iodobenzene (3) and chloroiodobenzenes (7), respectively, at the expense of biaryl. In air, chlorobenzene and1produce chlorophenols (8), biaryl then being a minor product.Hydroxyl radicals produced from1abstract hydrogen from benzene to give phenyl radicals (Ph•) which, in nitrogen, arylate benzene. From isomer distributions of7and of4it is inferred that hydrogen abstraction from chlorobenzene leads to chlorophenyl radicals, with a ratioo/m/p∼ 24/52/24. With chlorobenzene,ipsosubstitution, PhCl +•OH→PhOH, also takes place. In the presence of oxygen or iodine, formation of biaryls involves irreversible addition of (chloro)phenyl radical, the intermediate adduct radicals reacting with oxygen or iodine. In nitrogen, however, the first step in arylation is reversible. Apart from undergoing O‐O bond homolysis,1is attacked by•Me (formed from Me3CO•) and, to some extent, by aryl radicals. A large arene/1intake ratio (>100), or the addition of either iodine or air suppresses ‐ or even prevents ‐ free‐radic

ISSN:0165-0513    

DOI:10.1002/recl.19841031003

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThe potential of a number of tetraaza‐macrocyclic complexes of cobalt and nickel to mediate the photoreduction of carbon dioxide has been studied. Carbon monoxide and hydrogen are the main products, which result from illumination of an aqueous solution containing Ru(2, 2′‐bipyridine)2+3as sensitizer, ascorbic acid as sacrificial eletron donor and a tetraaza‐macrocyclic complex as relay. Their ratio strongly depends upon the relay compound used. The complexes can be used as electrocatalysts for CO2reduction at a mercury electrode since they lower the overpotential for CO2reduction showing turnover numbers/hour of approximately 3. A minimum potential is required to induce reaction of electrocatalysts and CO2(and H2O).Finally, the redox properties of the macrocyclic metal complexes at p‐GaP and p‐GaAs photocathodes in acetonitrile are compared with those obs

ISSN:0165-0513    

DOI:10.1002/recl.19841031004

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractTwo different types ofDiels‐Alderadditions to morphinan‐6, 8‐dienes have been found. 6‐Demethoxythebaine (2) yielded ethyl 4, 5α‐epoxy‐3‐methoxy‐N‐methyl‐6, 14‐ethenoisomorphinan–7α‐carboxylate (3) with ethyl acrylate, in analogy to the reaction with thebaine. The ester3was converted into the alcohol4, of which the 3‐methoxy ether was hydrolyzed to yield5. Similarly,2gave the 7α‐acetyl‐6, 14‐ethenoisomorphinan7with methyl vinyl ketone. The latter compound was converted into4using methylmagnesium iodide. With propylmagnesium bromide,7afforded four compounds; two are new etorphine analogues (8and9), to which we were able to assign the absolute configuration; the other two are the Grignard reduction products10and11.When the 4, 5α‐epoxy bridge of2is first opened, theDiels‐Alderreaction with methyl vinyl ketone proceeds from the other side of the diene system yielding the 7β‐acetyl‐6, 14‐ethenomorphinan6, which belongs to a novel class of rigid morphinans.Preliminary pharmacological screening of5, 8

ISSN:0165-0513    

DOI:10.1002/recl.19841031005

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19841031006

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractIrradiation of neat 1, 3, 5‐hexatriene with light (λ>334 nm) in the presence of 0.2 mol% of copper(I) trifluoromethanesulfonate affords a mixture of three dimerization products in an overall yield of 80%, consisting of 86% 4‐(E‐1, 3‐butadienyl‐3‐vinyl‐1‐cyclohexene 2˜(cis 2˜/trans2˜∼ 1˜) and 14% 1Z, 3E, 7E, 9Z‐1, 3, 7, 9

ISSN:0165-0513    

DOI:10.1002/recl.19841031007

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY