摘要:

AbstractThe prerequisites for applicability of the Kubelka‐Munk theory of diffuse reflectance for obtaining characteristic color curves of powders are discussed, and some experimental support for the theory is given. Methods are described for eliminating surface reflection, which is always superimposed upon the diffuse reflection and which therefore distorts the spectrum. The effect of interactions with the adsorbent on the reflection spectra of adsorbed molecules is demonstrated by means of examples, and the special suitability of the method for investigating chemisorption and for following reactions at phase boundaries is pointed out. By analogy to the Beer‐Lambert law, the Kubelka‐Munk function can be used for quantitative photometric analysis. The reflectance curves of white standards are presented, and measurements relating to the conditions for “infinitely thick layers” are reported. The scattering coefficient of the Kubelka‐Munk functions has been estimated for several samples of color‐filters as a functions of grain‐size and wavelength. The effect of moisture on diffuse reflectance spectra is discussed, and details of the measuring technique

ISSN:0570-0833    

DOI:10.1002/anie.196303331

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196303411

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractIn the series of accounts of progress in the field of peptide synthesis, this review surveys the literature from the beginning of 1959 to the middle of 1962.

ISSN:0570-0833    

DOI:10.1002/anie.196303581

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractMonoketones react with hydrogen sulfide in the presence of basic catalysts to give geminal dithiols or thioketones. β‐Diketones are converted into monothiodiketones. α‐Diketones can be selectively reduced by hydrogen sulfide in the cold in the presence of secondary or tertiary amines to give hydroxy‐or mono

ISSN:0570-0833    

DOI:10.1002/anie.196303701

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractDihydroxydiarylmethane derivatives are formed by condensation of aromatic hydroxy and carbonyl compounds in the presence of acidic condensing agents at low temperatures or in the presence of bases at elevated temperatures. This article deals with formation and cleavage mechanisms in acid and basic media. As a result of the investigations reported, new methods of preparing unsymmetric dihydroxydiarylmethane derivatives and p‐alkenylphenols have been develope

ISSN:0570-0833    

DOI:10.1002/anie.196303731

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

摘要:

AbstractCleavage of N‐phenylpyridinium or N‐vinylpyridinium salts with secondary aliphatic amines leads to aromatic amino compounds or enamines which are often unobtainable by other routes. The other fragment, glutacondialdehyde or its monoanil, gives azulenes, as shown by Ziegler and Hafner, as well as König; these compounds can also be prepared from alkylpyridinium salts with cyclopentadienylsodium (Hafner). Syntheses of labile aldehydes which are otherwise difficult to obtain and of α‐ketocarboxylic acids, starting from pyridinium salts and proceeding via nitrones or α‐cyanoanils, are illustrated by many new examples. Benzimidazoles, benzothiazoles, and amidines are accessible from pyridinium salts via nitrones or α‐cyanoanils; cyanoanils can be transformed into quinoxalines (including xanthopterine), perimidines, etc. Furthermore, nitrosonaphthols and nitrosonaphthylamines react with pyridinium salts containing an active methylene group on the nitrogen, leading to new ring systems. Further synthetic possibilities arise from nucleophilic displacements of the pyridine in pyridinium salts by SN2 reactions. Combination of the route via nitrones with the methods of Arndt‐Eistert, Ortoleva‐King, or with chloromethylation constitutes a significant enlargement of its range of application. The formation of α‐cyanoanils from diazoketones permits synthesis of α‐keto‐β‐amino acids from α‐amino acids, or of phenylglyoxylic acids from b

ISSN:0570-0833    

DOI:10.1002/anie.196303801

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196303932

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196303942

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196303953

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.196303963

出版商:Hüthig&Wepf Verlag    

年代:1963

数据来源: WILEY