摘要:

AbstractMost sedimentary rocks contain small concentrations of finely divided organic material. With the aid of modern analytical methods, samples of such rocks can be examined in detail, and conclusions can be drawn concerning the origin of the organic substances. Intact or modified biogenic compounds such as paraffins, isoprenoids, alcohols, ketones, carboxylic acids, steroids, triterpenes, and porphyrins have been isolated from the soluble fractions of the organic material of many sediments and from identified fossils of various geological ages. Even Precambrian rocks contain biogenic substances, so that life forms must have existed more than three billion years ago. The main component of the organic material is “kerogen”, the complicated polymeric structure of which has not yet been establis

ISSN:0570-0833    

DOI:10.1002/anie.197102091

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractThe vibrational spectra of molecules labeled with2H,13C, and18O show that delocalization of double and single bonds in the six‐membered ring is complete in all the metal chelates investigated of 2,4‐pentanedione (acetylacetone), but not in 2,4‐pentanedione itself. Mercury, on the other hand, is bonded to the central C atom of the ligands. The NMR spectra of the metal chelates of 3‐mesityl‐2,4‐pentanedione and 3‐anthryl‐2,4‐pentanedione show that the chelate rings have no magnetic anisotropy comparable with that of benzene. A critical appraisal is made of the questions whether it is at all justifiable to attribute any “aromatic character” to such molecules and why all comparisons with the chemical reactivity of benzene have so far led to controversial conclusions concerning the character of the bonding in the metal chelate

ISSN:0570-0833    

DOI:10.1002/anie.197102251

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractThe term antibiotic sugar denotes the carbohydrate component of an antibiotic. Two alternative approaches are adopted for the synthesis of these neutral and amino sugars, many of which have unusual structures: One route starts from fairly simple non‐carbohydrate precursors, the other depending upon the modification of a carbohydrate precurso

ISSN:0570-0833    

DOI:10.1002/anie.197102361

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

摘要:

AbstractThe preparation and resolution of asymmetric organometallic compounds of the transition series with four different ligands on the metal atom are described. Some of the optically active complexes retain their configuration, while others undergo racemization in solution. Their properties and reactions are discussed. Centers of asymmetry at transition metal atoms can also be detected on the basis of the magnetic nonequivalence of diastereotopic groups. Information about the configurational stability of such compounds can be obtained by investigation of the temperature dependence of the nuclear magnetic resonance spectra.

ISSN:0570-0833    

DOI:10.1002/anie.197102491

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197102601

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197102611

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197102621

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197102631

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197102641

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197102651

出版商:Hüthig&Wepf Verlag    

年代:1971

数据来源: WILEY