摘要:

AbstractFor atactic poly(methacrylic acid) (PMAA) and poly(ethacrylic acid) (PEA) the conformational transition from a compact coil to a random coil upon ionization in aqueous solution is revealed by an analysis of the potentiometric titration curves. The treatment, proposed byStrauss, is couched in terms of successive ionization constants of a suitably sized subunit of the polymer chain. Consideration of the bimodal population distribution indicates that the conformational transition in PEA is more pronounced than in PMAA. This is most likely the result of the more hydrophobic side‐chain in PEA. In agreement with previous work, no “two‐state” conformational transition is observed upon ionization of poly(acrylic acid

ISSN:0165-0513    

DOI:10.1002/recl.19861051002

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractWe have isolated and characterized genomic clones for the ribosomal protein eL12′ from the brine shrimpArtemia.The gene consists of 5 exons spanning a region of more than 11 kilobases on theArtemiagenome. DNA sequencing of the region upstream from the transcription initiation point shows the presence of sequence elements that are similar to sequences specific for yeast ribosomal protein genes. This finding suggests a common mechanism for the regulation of ribosomal protein gene expression in eukaryote

ISSN:0165-0513    

DOI:10.1002/recl.19861051003

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe13C NMR spectra of a wide range of monomericpara‐substituted nitrosobenzenes have been determined and the results related to a wide range of published data for otherpara‐disubstituted benzenes. It is shown that the nitroso substituent exercises a different pattern of effect for the13C chemical shifts at the ipso C atom from at least twenty eight other substituents. It is noted that when theparasubstituent is a π‐donor, the nitroso group functions in a different manner from that operative when theparasubstituent is a π‐acceptor, a general possibility that has already been suggested in the recent l

ISSN:0165-0513    

DOI:10.1002/recl.19861051004

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

Abstract(2,2′‐Bipyridine)diethylpalladium(II) reacts with electron‐deficient olefins (methyl acrylate, acrylonitrile, dimethyl fumarate, dimethyl maleate, maleic anhydride, fumaronitrile and tetracyano‐ethylene) to produce, with the exception of acrylonitrile, almost exclusivelyn‐butane as the product of reductive elimination. Apart from methyl acrylate and acrylonitrile, organometallic reaction products, (2,2′‐bipyridine)olefinpalladium(0) complexes, are isolated. The temperature dependence of the1H NMR and13C NMR spectra of the fumaronitrile complex demonstrates reversible dissociation of the olefin. The thermolysis of the diethylpalladium complexes with 4,4′‐dimethyl‐2,2′‐bipyridine oro‐phenanthroline as ligands leads to no change in behaviour. (2,2′‐Bipyridine)di‐n‐propylpalladium shows, upon thermolysis, the same product distribution as does the diethyl complex, i.e. propane/propene in the absence of olefin andn‐hexane in

ISSN:0165-0513    

DOI:10.1002/recl.19861051005

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe Z‐syn‐locked 1,1′‐methylene‐2,2′‐pyrromethen‐5(1H]‐one1, prepared in 45% yield in a one‐pot reaction from the previously reported 1,1′‐methylenebis(pyrrole‐5‐carbaldehyde) (8), exhibits a brilliant fluorescence with a high quantum yield (1.0) in contrast to the parent 2,2′‐pyrromethen‐5[1H]‐one systems. The λmaxof emission and the quantum yield are solvent dependent. Catalytic reduction of 1 affords the 3,4‐dihydro derivative2in 80% and the 2,3,4,6‐tetrahydro derivative3in 80% and 95% yields, respectively. Compounds2and3exhibit no fluorescence, however2shows a very efficient photoFries‐type rearrangement. Advanced1H NMR techniques had to be applied in order to obtain the complete analysis of the1H NMR spectrum of3, which showed the conformatio

ISSN:0165-0513    

DOI:10.1002/recl.19861051006

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractIrradiation of the title compound (6) with a broad spectrum lamp at room temperature afforded 2‐methylidene‐1,2,3,4‐tetrahydronaphthalene (8) and 2‐methylnaphthalene (7). Apart from8, irradiation of6at −45°C also afforded 5‐methylbenzobicyclo[3.1.0]hex‐2‐ene (12) 1‐methylidene‐2‐(2‐tolyl)cyclopropane (13) as well as a small amount of 2‐methyl‐1,4‐dihydronaphthalene (14). Both12and13originate from the ring‐opened product of6. Compound14is probably formed via a retro di‐π‐methane rearrangement from12.Irradiation of6inn‐propylamine afforded the same photopro

ISSN:0165-0513    

DOI:10.1002/recl.19861051007

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractLiquid Xenon (LXe) appears to be an ideal solvent for the study of reactive intermediates in photochemical reactions because of its complete inertness and transparency in both the IR and UV/Visible spectral regions. Photolysis of a H2‐doped solution of W(CO)6in LXe at 193 K leads to the formation of W(CO)5H2having CO stretching modes at 2098.4 (A21), 1972.2 (E) and 1970.5 cm−1(A11) and v(H‐H) at 2707 cm−1. From a comparison of these CO stretching frequencies with those of other W(CO)5L complexes it is concluded that the W(dπ) → H2(σ*u) interaction is stronger than expected th

ISSN:0165-0513    

DOI:10.1002/recl.19861051008

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractAn efficient multigram synthesis of optically pure (S)‐ and (R)‐citramalic acid is descri

ISSN:0165-0513    

DOI:10.1002/recl.19861051009

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThemetaphotocycloaddition of fluorobenzene and disubstituted fluoroarenes to cyclopentene has been investigated. From the effects of the various substituents and the varying product ratios it can be concluded that the reaction must proceed via a polar mechanism.

ISSN:0165-0513    

DOI:10.1002/recl.19861051010

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractEnamines of cyclodecanone and cyclododecanone (1a‐d) react with dimethyl acetylenedicarboxylate (DMAD) in an apolar solvent via (2 + 2) cycloaddition and conrotatory opening of the cyclobutene ring in3to give thecis,trans‐cycloalkadienes5a‐din yields of 44–85%. The compounds5do not undergo further thermal or photochemical transformation of thecis,transmoiety. In methanol, the enamines react with DMAD to give bicyclo[7.2.1]dodecene (8a) or bicyclo[9.2.1]tetradecene (8band8c) derivatives. These reactions take place via intramolecular nucleophilic addition of the enamine moiety to the α‐methoxycarbonyl group in10, which is formed from the intermediate Michael adduct9.The structure of8bwas determined by single‐crystal X

ISSN:0165-0513    

DOI:10.1002/recl.19861051011

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY