摘要:

AbstractThe35Cl‐NQR spectra of 45 chlorosubsitituted acetanilides, ClxC6H5−xNHCOCH3−yCly, were investigated and the temperature dependence of some spectra, especially of monochloroacetic acid derivatives, was measured. A preliminary assignment of the NQR frequencies is given. A correlation between NQR frequencies and substituent parameters permits the study of the substituent effect of the acetamido group, NHCOCH3−yCly. The chloro‐substitution in the side chain of the acetanilides seems to have no noticeable influence on the35Cl‐NQR frequencies of the chlorine atoms at the benzene ring. The NQR frequencies of the chlorine atoms in the chloroacetamido group are, on the other hand, insensitive to substitutions at the benzene nucleus. The possibility of steric influences on the NQR spectrum ofortho‐chloro‐substituted acetanilides is discussed. The investigation further confirms that a crystal field effect of about ±500 kHz must be considered in the interpretation of NQR spectra of chlorob

ISSN:0030-4921    

DOI:10.1002/mrc.1270030202

出版商:John Wiley&Sons Limited    

年代:1971

数据来源: WILEY

摘要:

AbstractLes 2 oxazaphospholanes étudiés ici donnent des spectres de RMP qui, après découplage du phosphore, peuvent ětre analysés comme des ABXY. Sur les huit solutions possibles, six peuvent ětre aisément éliminées et deux expériences de ‘tickling’ permettent de choisir entre les deux restantes. L'accord entre les spectres calculés, avec le programme LAOCOON III, et les spectres expérimentaux est très bon. La doubel résonance hétéronucléaire, les expériences de ‘tickling’ ou d'‘Indor’ permettent de déterminer les signes relatifs des constantes de couplages3J(POCH) et3J(PNCH). On vérifie également par l'expérience qu'aux signes négatifs de2JHH correspondent des signes positifs pour les3JHH. Quant à la conformation du cycle, si on ne peut l'établir avec certitude, on peut cependant constater, par comparaison avec les dioxaphospholanes, que l'introduction d'un groupement NCH3ne semble pas introduire de dissymétrie et que le couplage3J(PNCH) semb

ISSN:0030-4921    

DOI:10.1002/mrc.1270030203

出版商:John Wiley&Sons Limited    

年代:1971

数据来源: WILEY

摘要:

AbstractUne barrière de rotation de faible valeur autour de la liaison NCO est mise en évidence dans les urées de formule CH3NHCONHR (R  H, CH3). Les thiourées correspondantes sont examinées afin d'étendre l'étude comparative des systèmes carbonyle‐thiocarbonyle. Les paramètres RMN et les grandeurs thermodynamiques liées au processus d'isomé

ISSN:0030-4921    

DOI:10.1002/mrc.1270030204

出版商:John Wiley&Sons Limited    

年代:1971

数据来源: WILEY

摘要:

AbstractDouble and triple nuclear magnetic resonance experiments performed at 100 MHz demonstrate the existence of long range1H—1H couplings through epoxides. In a series of epoxycontaining sesquiterpenoids, interactions between protons separated by up to six sigma bonds were detected. These interactions may have origins similar to the well‐known allylic and homoallylic couplings found in carbon‐carbon double bonded compounds, although they are much smaller in the epoxy systems. We propose to name them as ‘epoallylic’ and ‘epohomoallylic’ interactions. Some couplings are observed directly, whereas in other cases only an improvement in resolution is seen during multiple irradiation experiments. Even in these latter cases the areas of the observed peak do not change upon multiple irradiation which demonstrates the absence of nuclear Overhauser effects. The stereochemistry of some asymmetric centers of the compounds studied is deduced fro

ISSN:0030-4921    

DOI:10.1002/mrc.1270030205

出版商:John Wiley&Sons Limited    

年代:1971

数据来源: WILEY

摘要:

AbstractThe applicability of W½, the line‐width at one‐half height corrected for field inhomogeneity and couplings, for characterization of nuclear magnetic resonance line shapes generated by exchange averaging of chemical shifts has been investigated for the case PA= PB. The Gutowsky‐Holm equation, simplified by the assumption of a large T2º such that T 2º−1= 0, was used to produce a family of curves relating W½corrected to the rate of exchange for various ΔvABvalues.The rate of internal rotation about the CN amide bond has been studied in neatN,N‐dimethyl‐formamide between 79·5 and 159° by the W½method and the results, Ea= 24·9 and 24·1 Kcal/mole at 60 and 100 MHz do not agree with those recently reported by Rabinovitz and Pines, Ea= 20·5 Kcal/mole obtained by the total line shape method. For neatN,N‐dimethylacetamide and for solutions of DMA in dimethylsulfoxide‐d6, application of the W½method yielded Ea, ΔH‡ and ΔS‡ values which are in excellent agreement with those obtained by Neuman and Jonas for DMA‐dεusing a total line shape analysis. The thermodynamic parameters for neatN,N‐dimethylcarbamoyl chloride obtained by the total line shape and W½methods are also in excellent agreement, 16·4 and 16·8 Kcal/mole for Eaand 15·8 and 16·2 Kcal/mole for ΔH‡, respectively.The W½method was also used for the determination of the activation parameters for rotation about the carbon‐nitrogen bond in the following thioamides:N,N‐dimethylthiobenzamide, (Ea= 19.8 Kcal/mole),N,N‐diethylthiobenzamide, (Ea= 20·4 Kcal/mole),N,N‐dimethylphenylthio‐acetamide (Ea= 21·4 Kcal/mole). The results obtained for these thioamides are compared with the corresponding amides. SpecificallyN,N‐dimethylbenzamide andN,N‐diethylbenzamide were studied using the W½method and activation energies for rotation about the carbon‐nitrogen bond of 17·5 and 15·6 Kcal/mole, respectively, were found. The relative magnitudes of these parameters are discussed on the basis of molecular geometry of the thioamides. Attention is drawn to the fact that for structurally related amides and thioami

ISSN:0030-4921    

DOI:10.1002/mrc.1270030206

出版商:John Wiley&Sons Limited    

年代:1971

数据来源: WILEY

摘要:

AbstractThe benzene‐induced solvent effects upon the proton chemical shifts of various pyrazines, pyrimidines and theirN‐oxides are described. Larger chemical shift effects, implying closer benzeneheterocycle association, are noted in theN‐oxides as compared to the non‐oxidized heterocycles.The solvent‐induced chemical shift changes can be used to establish the site ofN‐oxidation in those instances where different isomers ca

ISSN:0030-4921    

DOI:10.1002/mrc.1270030207

出版商:John Wiley&Sons Limited    

年代:1971

数据来源: WILEY

摘要:

AbstractThe INDOR technique appears to be a very useful and rapid tool for the detection of hidden proton lines as an aid in the elucidation of the structure of complex organic molecules. The experimental conditions for obtaining optimum results in a limited time are discussed. Analysis of the INDOR spectra of a number of selected spin systems are given; these show the capabilities of this method. Examples are given in which this technique is applied.

ISSN:0030-4921    

DOI:10.1002/mrc.1270030208

出版商:John Wiley&Sons Limited    

年代:1971

数据来源: WILEY

摘要:

AbstractThe NMR spectrum of benzaldehyde oriented in the nematic phase of a mixture ofp‐(p‐ethoxyphenylazo)phenylheptanoate andp‐(p‐ethoxyphenylazo)phenylundecylenate is analysed. It is demonstrated that the data are inconsistent with models in which the aldehyde group freely rotates or has minimum energy when it is perpendicular to the ring plane. The barrier height to rotation, however, cannot be obtained, nor is it possible to discriminate between the two possible solutions in which the averaging planar forms do or do not reorient in the liquid crystal between successive internal ro

ISSN:0030-4921    

DOI:10.1002/mrc.1270030209

出版商:John Wiley&Sons Limited    

年代:1971

数据来源: WILEY

摘要:

AbstractThe chemical shift non‐equivalence of the methylene protons adjacent to the quaternary nitrogen in compounds of the type has been investigated. The behaviour of the examined compounds is interpreted in terms of different rotation rates around the three CN⊕bonds. The vicinal and geminal coupling constants of the non‐equivalent methylene protons are also reported and discussed in terms of steric

ISSN:0030-4921    

DOI:10.1002/mrc.1270030210

出版商:John Wiley&Sons Limited    

年代:1971

数据来源: WILEY

摘要:

AbstractThe PMR spectra of mytilitol at 60, 100 and 220 MHz are presented; the latter confirms the structure1.

ISSN:0030-4921    

DOI:10.1002/mrc.1270030211

出版商:John Wiley&Sons Limited    

年代:1971

数据来源: WILEY