摘要:

AbstractMass spectrometry is one of the most important analytical tools in chemistry, biology, medicine and related areas. During the past 30 years, methods have been developed, both for the qualitative as well as the quantitative analysis of a wide variety of substances. The introduction of lasers into chemistry has also profited mass spectrometry, since its nonlinear properties and its tunability open up fundamentally new frontiers. Multiphoton ionization mass spectrometry combines UV‐spectroscopy and mass spectrometry, thus providing a two‐dimensional method that enables substance‐specific and even state‐specific analyses. This progress report presents the fundamentals and possibilities of MUPI mass spectrometry and discusses investigations on amino acids, peptides, chlorophylls and sugars. For each substance, multiphoton ionization can be tuned in such a way that only the molecular ion is formed. An increase of laser intensity induces substance‐specific fragmentations of the molecule, thus contributing to a quick and easy identification of the

ISSN:0570-0833    

DOI:10.1002/anie.198804473

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractWhat can a chemist do with a few nanograms of valuable organic substance, pure or impure? The answer may be, a great deal. Its components may be quantified, separated, isolated, degraded, derivatized, extracted by solvent partition, as well as the more obvious recording of their mass spectra. Provided a substance is not contaminated by large quantities of solvent, manipulations are possible without much loss or dilution. Necessity is the mother of invention. The examples given in this review show what can be accomplished today in nanochemistry and should act as a stimulus to direct the scientist to discover other applications appropriate to his needs and his circumstances. The examples are largely taken from the field of insect chemistry, but their general applicability is emphasized. This review illustrates how gas chromatography and reaction gas chromatography, alone or combined with mass spectrometry are potent tools in the hands of the chemist to deduce the unique structure of volatile organic substances available only in nanogram quantities.

ISSN:0570-0833    

DOI:10.1002/anie.198804601

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractFor the general public, science history and restaurant menus share a labeling style. Like Melba peach, Soubise sauce, or tournedos Rossini, many a scientific discovery is credited to a single thinker or tinkerer. Such ultrasimplification rubs into oblivion other important contributors or codiscoverers. The discovery of noble‐gas compounds conforms to such a stereotyped and mythic view: according to the standard account,Neil S. Bartlett, then at the University of British Columbia, made it a quarter of a century ago on March 23, 1962. We do not attempt here a full and definitive history; it would be premature and we do not have the space. Rather, we shall document the concept and the earlier attempts at synthesis–they antedatedBartlett's success by three decades. The motivation for this note may be summarized in the following questions: (1) What sort of insight and input were those ofLinus Pauling? (2) What were the likely causes for failure of the attempt byYostandKayeto synthesize noble‐gas fluorides in the 1930s? (3) Were there other researchers who envisioned a noble‐gas rea

ISSN:0570-0833    

DOI:10.1002/anie.198804791

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractAn exact knowledge of the structure, dynamics, and reactions of molecules provides the key to understand their functions and properties. NMR spectroscopy has developed, through the introduction of two‐dimensional methods, into the most important method for the investigation of these questions in solution. A great variety of different techniques is available. However, for their successful application not only the appropriate equipment is required, but also the right choice of experiments and optimum measurement parameters, as well as a careful evaluation of the spectra. This contribution describes the necessary background for modern NMR spectroscopy. With the aid of the so‐called product operator formalism it is possible to understand pulsed Fourier transform NMR spectroscopy both qualitatively and quantitatively. Very few, readily understandable assumptions are sufficient for confident application of these methods. This article attempts to introduce in a simple manner this formalism as well as phase cycles necessary for the understanding of pulse sequences, and to train the reader through the discussion of several 2D NMR techniques. An overview of the most important techniques is given in the second part of this arti

ISSN:0570-0833    

DOI:10.1002/anie.198804901

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe cyclopropyl group—particularly in compounds such as cyclopropylmethanol, phenylcyclopropylamine, and cyclopropanone hydrate—has proved to be very useful in the study of enzyme reactions. Whether the cyclopropane ring is opened to form a radical or remains intact can provide much information about reactions occurring at the active s

ISSN:0570-0833    

DOI:10.1002/anie.198805371

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198805531

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198805551

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198805581

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198805601

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198805611

出版商:Hüthig&Wepf Verlag    

年代:1988

数据来源: WILEY