摘要:

AbstractThe time‐dependence of the polarized intensity ratio within a product molecule has been studied by a kinetic method. The kinetic analysis of polarized product formation shows that considerable changes in CIDNP ratios occur during the reaction but characteristic curves can be obtained under different experimental conditions. A method is proposed to evaluate the relative enhancement coefficients on the basis of these characteristic curves, and to obtain information on the kinetics of the reactio

ISSN:0030-4921    

DOI:10.1002/mrc.1270110202

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractUpfield substituent‐induced13C chemical shifts for aryl carbons of polymethyl substituted benzenes, phenols, anilines and thiophenols were investigated as a function of the proximity between substituents X and CH3(X = CH3, NH2, OH and SH). The results indicate that the induced shifts of the substituted aryl carbons are, in general, independent of the polar substituent but depend on the number of adjacent substituted aryl carbons. A −2.0 ppm upfield shift was found for a substituted aryl carbon adjacent to one substituted aryl carbon and a −3.8 ppm upfield shift for a substituted aryl carbon bound by two substituted aryl carbons. It is suggested that the near additivity of the upfield shifts is the result of changes in the bond order between the aromatic ring carbons in the region of the substituted aryl carbons due to distortion of the ring. The13C chemical shifts of the methyl substituents for methyl substituted phenols, anilines and thiophenols were determined, and it was found that the values could be predicted from the additivity parameters reported for the analogous methylbenzenes plus an additional pair‐interaction term associated with the through‐space electronic influence of the h

ISSN:0030-4921    

DOI:10.1002/mrc.1270110203

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractDie13C‐NMR‐Spektren einiger Bicyclo[3.1.0]hex‐3‐en‐2‐ole und Bicyclo[3.1.0]hex‐3‐en‐2‐one werden beschrieben. Die Bindungsparameter des Bicyclo[3.1.0]hex‐3‐en‐2‐ons werden aus der Kristallstruktur desendo‐6‐Methoxy‐1,3,6‐triphenylbicyclo[3.1.0]hex‐3‐en‐2‐ons abgeleitet. Mit der EHT‐Methode wird die Elektronendichte berechnet und mit den13C‐Verschiebungen korreliert. Als Vergleichsspektrum wird das13C‐NMR‐Spektrum eines Bicyclo[4.1.0]hepta‐1,5‐dionderivats analysiert. Die Einflüsse des an den Fünfring und an den Sechsring annellierten Cyclopropansystems werden miteinander verglichen. Während am Fünfring eine Konjugation zwischen der Carbonylgruppe und dem Cyclopropansystem auftritt, wird sie am Sechsring nicht beobachtet. Die Erklärung dafür wird auf di

ISSN:0030-4921    

DOI:10.1002/mrc.1270110204

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractThe13C spectra of a series of 21 10‐methyl‐trans‐decalins have been recorded to explore in greater detail the deshielding antiperiplanar γ effects found earlier in a few of these derivatives. From the data for the series complete assignments for each compound were obtained, permitting an analysis of the shielding effects of the methyl and hydroxyl

ISSN:0030-4921    

DOI:10.1002/mrc.1270110205

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractThe carbon resonances of quinacrine, chloroquine, acranil, 4‐aminopyridine and 9‐aminoacridine in D2O solution have been assigned. Resonance assignments were made using empirical shift parameters, partial proton decoupling, selective proton decoupling and by interpretation of the fully coupled spectra. The effect of pD on the carbon chemical shifts for quinacrine and chloroquine over the range of about 4.5 to 8.5 was observed. Characteristic chemical shifts for the aromatic ring carbons for deprotonation of the heteroaromatic nitrogen were obser

ISSN:0030-4921    

DOI:10.1002/mrc.1270110206

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractLes effets de substitution alkyle sur les déplacements chimiques des carbonesspd'alcynes aliphatiques sont analysés par la méthode DARC PELCO estimant les perturbations liées à l'introduction de sites localisés dans l'Environnement Limité, Concentrique, Ordonné des carbonessp, décrit par génération progressive à partir du foyer origine –CC..Une corrélation de site ‘topologie‐δ’ est proposée et son aptitude à la prévision des déplacements chimiques est vérifiée sur une population de 55 alcynes linéaires ou fortement ramifiés correspondant à un domaine expérimental de 25,2 ppm.Cette étude met aussi en éevidence (i) l'indépendance des effets des groupes alkyles portés par la triple liaison; (ii) leur atténuation lorsque croǐt la connectivité des sites substitués; (iii) la faible importance des effets γπ; (iv) l'additivité des incréments de perturbation de site—sans termes d'interaction—jusqu'à une frontière correspondant aux groupes –C(H,Me,tBu) et –C(Me2,tBu).Un modèle simplifié est proposé à partir d'un graphe partiellement ordonné et à des fins de calcul rapide des δ, les effets globaux des radicaux alkyles sont caractérisés et exprimé

ISSN:0030-4921    

DOI:10.1002/mrc.1270110207

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractThe13C,1H spin–spin coupling constants for benzene and tropylium fluoroborate have been measured from the13C NMR spectra of [D5]benzene and the [D6]tropylium ion using a new experimental technique which employs highly deuterated compounds and2D‐decoupling. For benzene the new data are in good agreement with earlier results. For the tropylium ion we find1J= 166.79,2J≃ 0,3J= 9.99 and4J= (−)0.64 Hz. Secondary isotope effects for13C chemical shifts, including one over four bonds, are r

ISSN:0030-4921    

DOI:10.1002/mrc.1270110208

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

Abstract1H and13C data are presented for eleven 1,3,5‐triazaadamantane derivatives. Ring protonation produces a decrease in1H screening and the opposite effect in the corresponding13C spectrum. The trisaryl substituted compounds appear to exist as a single isomer with diequatorial and monoaxial substituent

ISSN:0030-4921    

DOI:10.1002/mrc.1270110209

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

Abstract6Li,7Li and13C spin–lattice relaxation and NOE data are reported for methyllithium, butyllithium and phenyllithium with6Li T1values found in the order of tens of seconds and their relaxation 2–3 orders of magnitude less efficient than that for7Li. The data indicate that6Li is substantially relaxed by the intramolecular6Li–1H mechanism, whereas both quadrupolar and6Li–7Li dipolar relaxation are minor processes. The non‐linearity of the Arrhenius curve for Me6Li is compatible with a small spin–rotation contribution. Since6Li in solution behaves essentially as a spin‐1/2 nucleus, it represents, in spite of its lower magnetic moment and overall sensitivity, an attractive alternat

ISSN:0030-4921    

DOI:10.1002/mrc.1270110210

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

ISSN:0030-4921    

DOI:10.1002/mrc.1270110201

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY