摘要:

MO‐LCAO‐Berechnungen an Polymethinen. XII. Zur Intensität intramolekularer Charge‐Transfer‐AbsorptionsbandenEinige meropolymethinische und zwitterionische Farbstoffe werden aus zwei molekularen Teilstrukturen zusammengesetzt gedacht, die entweder Donator‐ oder Acceptor‐eigenschaften besitzen. In diesem Bild rührt die Farbbande von einem Charge‐Transfer‐Übergang her. Hohe Übergangswahrscheinlichkeiten treten auf, wenn die Charge‐Transfer‐Konfigurationen mit der No‐Bond‐Grundzustandskonfiguration überlappen. Aufgrund von Überlegungen, die von den Grenzorbitalen der Fragmente ausgehen, lassen sich Strukturen angeben, welche bei langen Wellenlängen und mit hoher Intensität absorbieren. Die Schlußfolgerungen stehen in Übereinstimmung mit numerischen Ergebnissen von PPP‐Konfigurationsanalysen und LHM

ISSN:0021-8383    

DOI:10.1002/prac.19803220102

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Nucleophilic Substitutions to Carbonic Acid Derivates. XII. Kinetics and Mechanism of the Reaction of N‐Nitro‐N‐alkyl‐urethanes with Primary Aliphatic AminesThe aminolysis of N‐alkyl‐N‐nitrourethanes takes place, as the kinetical studies demonstrate, by means of several consecutive steps.The nucleophilic attack of the amine (first step; reaction B), as well as the proton‐transfere (second step; reaction C), are quick pre‐equilibres, followed by the slow, rate‐determining elimination of the nitramino‐group (reaction D).During the deprotonation, an intermediate with two to the nitramino‐group antiperiplanar orbitals is formed, providing the necessary mesomeric assist

ISSN:0021-8383    

DOI:10.1002/prac.19803220103

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Analysis of Hydrocarbons by Means of the Mass Spectrometry. V. Fragmentation of Monocyclic Hydrocarbons as a Function of the Ring SizeThe E.I.‐spectra of the cycloalkanes CnH2n(n = 5 – 14) and of the cycloalkenes CnH2n‐2(n = 5 – 12) exhibit strongly influence of the ring strain energies on the stability of molecular ions. Medium‐sized cycloalkanes and cycloalkenes (n = 9 – 11) show exceptional behaviour under the conditions of the electron impact ionization, which is discussed on the base of ring str

ISSN:0021-8383    

DOI:10.1002/prac.19803220104

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Analysis of Hydrocarbons by Means of the Mass Spectrometry. VI. The Influence of the Ring Size and the Konfiguration on the Fragmentation of Bicyclo(n.1.0)alkanes and their Halogen Derivatives by Electron ImpactThe mass spectra of cis and trans bicyclo(n.1.0)alkanes and their halogen derivatives are discussed. The ring strain energies of these compounds influence the stability of their molecular and fragment ions.

ISSN:0021-8383    

DOI:10.1002/prac.19803220105

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Analysis of Hydrocarbons by Means of Mass Spectrometry. VII. The Fragmentation of Bicyclo(n.2.0)alkanes by Electron ImpactThe mass spectra of cis‐bicyclo(n.2.0)alkanes (n = 3–6) are characterized by small intensities of molecular ions and large intensities of (MC2H4)+‐ions. The stability of M+and the main fragmentations are a function of the ring size of the seco

ISSN:0021-8383    

DOI:10.1002/prac.19803220106

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Kondensation von Arylbenzylketonen mit DimethyldiglycollatPhenyl‐, p‐Tolyl‐ und p‐Chlorphenyl‐benzylketone kondensieren mit Dimethyldiglycollat in Gegenwart von Natriumhydrid in guten Ausbeuten zu den entsprechenden Z‐Halbestern2a–e. Struktur und Konfiguration der Halbester wurde durch chemische und spektroskopische Bef

ISSN:0021-8383    

DOI:10.1002/prac.19803220107

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Studies on UV/VIS Absorption Spectra of Azo Dyes. III. Empirical Absorption Increments Derived from Azobenzenes and their Relationship to Reactivity Constants, Spectroscopic Substituent Constants and Ionisation PotentialsAbsorption increments ϵ which specifically characterize the substituents are derived from the difference in exitation energy between azobenzene and monosubstituted azobenzenes. These increments have been found to predict accurately the effect of substituents of the long wave π → π*band of polysubstituted azobenzenes.Comparison of the ϵ values with HAMMETT‐σ reactivity constants reveals direct proportionality between the two sets of constants. There is also a direct proportionality between the increments and spectroscopic substituent constants introduced by BLOORand COPLEY. Furthermore, a correlation of the ϵ values with the ionization potentials of substituents

ISSN:0021-8383    

DOI:10.1002/prac.19803220108

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Reactions with N‐Acylimino‐dithiocarbonic‐acid‐diesters.Reactions of N‐acylimino‐dithiocarbonic‐acid‐S,S‐diesters 1 with nucleophilic com‐pounds present new possibilities to synthesize heterocycles. With amines1areacts by mono‐ and disubstitution, respectively, of methylthio‐groups to isothioureas2and guanidines3, with 1,2‐bi‐nucleophilic arenes to benzoheterocycles4, with aliphatic diamines to imidazolidines5, pyrimidines6, diazepines7and the hexamethylene‐diamine‐derivatives8. 1areacts also with hydrazines to 1,2,4‐triazoles9and with hydrazides to the thiosemicarbazones10or 1,3,4‐oxadiazoles11. Heterocyclisations of1with guanidines, thiourea, salts of thiourea and amidines give the 1,3,5‐triazines12, 14, 15and16. N‐benzoyl‐dithiocarbonic‐acid‐methylester ‐amid reacts with CH‐acidic compounds to thiazoles17. The structures of the final products are determ

ISSN:0021-8383    

DOI:10.1002/prac.19803220109

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Diene Oligomerization. XV. Palladiumcomplexcatalyzed Telomerization of Butadiene with Amines and Dimerization in the Presence of KetoximesButadiene reacts with primary or secondary amines and with the homogeneous catalytic system bis‐acetylacetonatopalladium‐(II)/triphenylphosphine to form 1‐amino‐octa‐2,7‐dienes. The rate and the selectivity of the reaction increase in presence of cocatalysts as triarylphosphates instead of triphenylphosphine and if the reaction proceeds in a protic media — in alcohols, water or lower carboxylic acids. A number of 1‐aminoocta‐2,7‐dienes were prepared. If oximes act as organic nitrogen compounds, only n‐octa‐1,3,7‐triene is selectively formed. Schiff' bases aldolisate under the c

ISSN:0021-8383    

DOI:10.1002/prac.19803220110

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY

摘要:

Die Konkurrenzkinetik der wolframat‐ und molybdationenkatalysierten Epoxidierung von Crotonaldehyd durch WasserstoffperoxidDie Konkurrenzkinetik der Epoxidierung von Crotonaldehyd durch Wasserstoffperoxid in Gegenwart von Natriumwolframat oder Natriummolybdat wird untersucht.Natriumwolframat ist ein wirksamerer Katalysator bei der Umsetzung von Crotonaldehyd in 2,3‐Epoxybutyraldehyd. Die Reaktion ist bezüglich Substrat und Katalysator 1. Ordnung, bezüglich Wasserstoffperoxid 0. Ordnung.Ein mit den gefundenen Abhängigkeiten übereinstimmendes Geschwindigkeitsgesetz wird aufg

ISSN:0021-8383    

DOI:10.1002/prac.19803220111

出版商:WILEY‐VCH Verlag GmbH    

年代:1980

数据来源: WILEY