ISSN:0165-0513    

DOI:10.1002/recl.19821010501

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19821010502

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractA physico‐chemical description of the extended X‐ray absorption fine structure (EXAFS) phenomenon is given and experimental methods for its measurement in transmission mode are indicated. Pros and cons of various procedures for careful evaluation of the experimental absorption data are described, which comprise background removal according to Victoreen's relation or by polynomial fitting and criteria for Fourier filtering methods are given. Three different approaches for EXAFS signal analysis are discussed namely fitting with parametrized amplitude and phase functions, comparison of experimental data with theoretical EXAFS spectra and Fourier transform techniques; the limits of applicability of these procedures are indicated. A critical evaluation is given for the various methods for correction of the resulting radial distribution function in order to comply with crystallographic distances. The determination of coordination numbers is discussed and the procedures are illustrated with results for metallic titanium, rutile and anat

ISSN:0165-0513    

DOI:10.1002/recl.19821010503

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractA new inverse‐addition, low‐temperature procedure for lithium‐ammonia reductions has been developed. Using this method it has been demonstrated that the reduction of ethyl 5,5‐(ethylenedioxy)‐8β‐hydroxy‐4aβ‐methyl‐2‐oxo‐2,3,4,4a,5,6,7,8‐octahydro‐1‐naphthalenecarboxylate (3) results in an unusualcis‐reduction product. The 8β‐hydroxyl group, low reaction temperature (–80°C) and addition of lithium‐ammonia to the substrate all proved to be necessa

ISSN:0165-0513    

DOI:10.1002/recl.19821010504

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

Abstract1‐Alkoxy‐3‐buten‐1‐ynes and the homologues ROCC‐CHCR′R″ (R′ and R″  H or alkyl, or R′R″  [CH2]5) have been obtained in satisfactory yields from allenic bis‐ethers RO‐CHCCH‐C(R′)(R″)OR and ethyllithium in diethyl ether. With excess ethyllithium, the enynes C2H5‐CC‐CHCR′R″

ISSN:0165-0513    

DOI:10.1002/recl.19821010505

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractMethyl α‐([13C,15N]isocyano)propionate was prepared starting from (±)‐[15N]alanine. The amino acid was converted into the methyl ester, which was formylated with acetic [13C]‐formic anhydride, to afford the methyl ester of N‐[13C]formyl[15N]alanine. Dehydration of the latter compound gave the isocyanide, which was polymerized with nickel chloride.1H,13C,15N NMR and IR data of the labelled compounds are

ISSN:0165-0513    

DOI:10.1002/recl.19821010506

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractCoalescence phenomena have been observed in the NMR spectra of a variety of 7‐substituted 1,3,5‐cycloheptatrienes upon varying temperature and/or solvent. Using two different methods, the energy of activation of the process responsible for coalescence has been determined. Within a group of structurally similarpara‐substituted phenyl sulphides a linear relation has been found between the energy of activation and the acidity constant of the corresponding benzenethiol, suggesting the occurrence of ion pairs. The relatively low energy of activation for the phenyl sulphides, when compared with the values of the phenyl sulphones, may result from the structure of the intermediate ion pairs.In addition to the above, a different exchange process between cycloheptatrienyl sulphides and tropylium salt via sulphonium ions has been obs

ISSN:0165-0513    

DOI:10.1002/recl.19821010507

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractExperimental verification of chirality in 2,4‐dimethyl‐3‐carbamoylpyridinium ca

ISSN:0165-0513    

DOI:10.1002/recl.19821010508

出版商:WILEY‐VCH Verlag    

年代:1982

数据来源: WILEY