摘要:

AbstractThe NMR linewidth of the formyl proton in dimethylformamide has been studied in the neat liquid and twelve organic solvents. It varies by more than one order of magnitude which is referred to solvent viscosity changes and to the protonation of dimethylformamide. The data do not allow the distinction between N‐ and O‐protonation without further knowledge of the solvent dependence of either the nitrogen‐14 spin lattice relaxation time or the spin‐spin couplin

ISSN:0030-4921    

DOI:10.1002/mrc.1270070902

出版商:John Wiley&Sons Limited    

年代:1975

数据来源: WILEY

摘要:

AbstractLe spectre de résonance magnétique protonique du diméthylamino‐2 méthyl‐3 oxazaarsolane‐1,3,2 est très sensible à la température et à la nature du solvant. L'analyse complète du spectre protonique à −48 °C dans le toluène deutérié montre que la molécule est dans une conformation privilégiée au niveau C‐4C‐5. Dans le nitrobenzène à +31 °C, le spectre de type A2X2indique un mouvement de libration autour de cette liaison. A température plus élevée un nouveau phénomène de coalescence peut être expliq

ISSN:0030-4921    

DOI:10.1002/mrc.1270070903

出版商:John Wiley&Sons Limited    

年代:1975

数据来源: WILEY

摘要:

AbstractThe13C NMR spectra of the most important hop bitter substances are analysed. All individual carbon atoms are assigned, except the oxygen bondedsp2carbon atoms. Most assignments are made partly by comparison with analogous compounds and partly by reference to literature data. Cross‐correlations with the1H NMR shifts are made for two main products and confirm the correctness of the assignments. All data are in agreement with the known structure

ISSN:0030-4921    

DOI:10.1002/mrc.1270070904

出版商:John Wiley&Sons Limited    

年代:1975

数据来源: WILEY

摘要:

AbstractDie13C‐NMR‐Spektren von dreizehn Cyclopropenonen, zwei Cyclopropenthionen, fünf zugehöriger Cyclopropenyliumsalze und von drei Cyclobutendionen werden tabelliert und disku

ISSN:0030-4921    

DOI:10.1002/mrc.1270070905

出版商:John Wiley&Sons Limited    

年代:1975

数据来源: WILEY

摘要:

AbstractThe rotational barrier in theN,N‐dimethylamide group is studied by proton NMR forN,N‐dimethylnicotinamide and two quaternary salts in aqueous solution. The carbon‐13 NMR spectra of a number of aromaticN,N‐dimethylamides are discussed. A roughly linear correlation is found between the ΔG≠values of the rotation barriers and the chemical shifts of the carbon atom substituted by the a

ISSN:0030-4921    

DOI:10.1002/mrc.1270070906

出版商:John Wiley&Sons Limited    

年代:1975

数据来源: WILEY

摘要:

AbstractDie13C‐NMR‐Spektren von fast 100 Monoterpenen zeigen, daß sie zur Charakterisierung derartiger Verbindungen sehr brauchbar sind. Besonders wertvoll ist diese Methode zur Klärung stereochemischer Probleme. Bis auf wenige Fälle folgen die beobachteten chemischen Verschiebungen den allgemeinen Regeln. Die Probleme der Messungen mit Verschiebungsreagenzien werden disk

ISSN:0030-4921    

DOI:10.1002/mrc.1270070907

出版商:John Wiley&Sons Limited    

年代:1975

数据来源: WILEY

摘要:

AbstractThe carbon‐13 spectra of a series of cyclohexanone, cyclopentanone and 2‐methylcyclohexanone enamines are reported. The influence of the amino component was studied in a series of enamino ketones. The spectra reflect the amount of p‐π overlap in the molecules and their conformation. Differences between 5‐and 6‐membered carbonyl components are

ISSN:0030-4921    

DOI:10.1002/mrc.1270070908

出版商:John Wiley&Sons Limited    

年代:1975

数据来源: WILEY

摘要:

AbstractL'équilibre conformational et la cinétique de l'inversion du cycle sont étudiés essentiellement à partir de la forma de raie du fluor. Une nouvelle méthode de calcul des grandeurs thermodynamiques d'activation est pré

ISSN:0030-4921    

DOI:10.1002/mrc.1270070909

出版商:John Wiley&Sons Limited    

年代:1975

数据来源: WILEY

摘要:

AbstractThe barrier to internal rotation about the NC bond and the E/Z configuration of someN‐acetyl andN‐formylindole derivatives have been determined and discussed in terms of electronic and steric effects. The barriers to internal rotation have been determined for certainN‐acetylcarbazoles and some newN‐formyl derivatives of carbazole. Experimental proof is also given, showing that contrary to the provisions of the classical model of carbonyl anisotropy, the protons (α andperipositions) next to the oxygen of the acyl group are displaced to high frequencies. This result allows one to determine the preferred configuration ofN‐acetyl derivatives of perimidine and 1H‐naphtho[1

ISSN:0030-4921    

DOI:10.1002/mrc.1270070910

出版商:John Wiley&Sons Limited    

年代:1975

数据来源: WILEY

摘要:

Abstract1H chemical shifts of quinoline, quinolineN‐oxide and the quinolinium ion were obtained by complete analysis of their NMR spectra and interpreted critically in an attempt to quantify the possible different effects acting on the shielding constant of protons in these systems. Semi‐empirical SCF calculations of electron charge densities and ring current contributions were also performed. It was found that the same effects that act on the shielding of protons directly bonded to the heterocyclic system also act, in an attenuated form, on the proton chemical shift of methyl groups in monomethyl derivatives. Vicinal coupling constants were rationalised in terms of π‐electron bond order and electro‐negativity of neighbouri

ISSN:0030-4921    

DOI:10.1002/mrc.1270070911

出版商:John Wiley&Sons Limited    

年代:1975

数据来源: WILEY