摘要:

AbstractThree new compounds, one with the molecular formula C6H8S and two corresponding to C7H10S have been isolated together with the main product, divinyl sulphide, from the reaction products of acetylene with sodium sulphide. Structure determination through1H and13C NMR with selective13C{1H} decoupling, showed C6H8S to be a new heterocyclic compound, 2‐thiabicyclo[3.2.0]hept‐3‐ene, and the two C7H10S compounds itsexo‐ andendo‐6‐methyl derivatives. Since the spectral parameters of these heterocycles were not known, all possible structures corresponding to the molecular formulae we

ISSN:0030-4921    

DOI:10.1002/mrc.1270110902

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractNous avons appliqué les approximations de Pascual et de Tobey pour évaluer le déplacement chimique d'un proton éthylénique dans le cas de substituants qui causent souvent des difficultés d'attribution de signaux. Les résultats des calculs empiriques de la différence d'écran entre les protons éthyléniques des deux configurationsZetEsont comparés aux valeurs expérimentales des déplacements chimiques dans une série d'aryl‐2 propène nitriles. La configurationZs'avère correspondre au proton le moins blindé et les effets de solvants observés concordent avec cette attribution. Lorsque la configurationZest prépondérante, sa nature est établie sans ambiguïté, car de très faibles quantités de l'autre isomèreEont pu ětre obtenues et étudiées. Les résultats de cette méthode sont satisfaisants et permettent de déterminer de nouveaux paramètres d

ISSN:0030-4921    

DOI:10.1002/mrc.1270110903

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractThe barrier to internal rotation around the phenyl–carbonyl bond in a series of stable protonatedp‐substituted acetophenones has been determined by means of low temperature13C NMR and total bandshape analysis resulting in a value of ΔG 273K≠= 48.1 kJ mol−1for the unsubstituted protonated compound. The energy results and the13C chemical shifts are in good agreement with the quasi‐planarity of the ground state inp‐substituted protonated acetophenones. The barrier heights are discussed in terms of contributions from steric and res

ISSN:0030-4921    

DOI:10.1002/mrc.1270110904

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractThe free energy of activation of the torsional barrier around the phenyl–carbonyl bond in a series of stable protonated α‐substitutedp‐methylacetophenones (p‐tolyl‐ where R = CH3, C2H5,i‐C3H7,t‐C4H9, CH2Cl, CHCl2, CCl3, CH2F, CHF2, CF3and CH2Br) has been evaluated by complete lineshape analysis of13C or proton low temperature NMR spectra. α‐Substitution by an alkyl group leads to a decrease of the barrier height due to both steric and electronic effects. For the halo compounds, steric and electronic effects of the substituents are in competition, leading to a very high ΔG≠value in protonated α,α,α‐trifluoro‐p‐methylacetophenone (63.2 kJ mol−1). In addition, the twist angle of the protonated carbonyl group has been tentatively evaluated by the use of t

ISSN:0030-4921    

DOI:10.1002/mrc.1270110905

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

Abstract1H and13C NMR data are reported for pentane‐2,4‐dione tellurium(II) compounds which contain a 6‐membered tellurane ring bearing methyl or ethyl substituents. The125TeCH coupling constants are particularly interesting in that they are highly stereospecific, viz. ∼60 Hz and 0–8 Hz for equatorial and axial protons, respectively, in the chair conformation.1J(TeC) and2J(TeCC) couplings lie in the ranges 118–146 Hz and 44–49 Hz, respectively. Geminal HCH couplings in these compounds (9–11 Hz) are lower than analogous values in tellurane or in cyclohe

ISSN:0030-4921    

DOI:10.1002/mrc.1270110906

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractMit Hilfe des CIDNP‐Effekts wird die Existenz von Radikalpaaren bei der Photolyse und Thermolyse von substituierten Phenyldiazoniumtetrafluoroboraten und Hydrochinon in Azetonitril aufgezeigt. Die Reaktion wird als Einelektronenübergang unter Ausbildung von Phenyldiazen undp‐Benzosemichinon formuliert. Dieses Radikalpaar verliert, entweder durch Photolyse oder Thermolyse, Stickstoff und kann eine Disproportionierung oder verschiedene Rekombinationen eing

ISSN:0030-4921    

DOI:10.1002/mrc.1270110907

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractA study of several linear and branched alkanes indicates that the temperature dependence of13C chemical shifts is a complex phenomenon in which several non‐additive effects may be operative. The chemical shift temperature coefficients dδ/dTdo, however, reveal some systematic trends which could be helpful in the assignments of13C resonances. An empirical equation is proposed (akin to that of Grant and Paul for13C chemical shifts) which accurately correlates all the data obtained near ambient temperatur

ISSN:0030-4921    

DOI:10.1002/mrc.1270110908

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

Abstract13C‐NMR‐spektroskopische Daten von elf Tetracyclo[4.1.0.02,4.03.5]heptanen, zwei Tetracyclo‐[5.1.0.02,4.03,5]octanen und zwölf Tricyclo[4.1.0.02,7]hept‐3‐enen werden mitgeteilt. In den Tetracycloheptanen üben 7‐ständige Halogene große δ‐Substituenteneffekte aus, die imendo‐Fall das C‐4‐Signal umca. 6 ppm nach tieferem Feld rücken und imexo‐Fall am C‐3‐Signal von der Natur des Halogens abhängige Hochfeldverschiebungen hervorrufen, wobei Fluor mit 9,1 ppm das Maximum erreicht. Ein Orbitalmodell zur Deutung der Hochfeld‐δ‐Effekte wird vorgeschlagen. Die fluorhaltigen Verbindungen enthüllen einen Zusammenhang zwischen den Substituenteneffekten und den zugehörigen13C19F‐Kopplungskonstanten. 5‐Substituenten in Tricycloheptenen sind γ‐Substituenten von C‐1, C‐3 und C‐7 und verschieben die Absorptionen dieser Kerne nach tieferem Feld. Die Substituentenabhängigkeit der Effekte folgt etwa jener in 1‐substituierten Adamantanen, ihre Gröβe übersteigt aber im Fall von C‐7 die Adamantanwerte um ein Mehrfac

ISSN:0030-4921    

DOI:10.1002/mrc.1270110909

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractCarbon‐13 NMR data are reported for a series of 1,2‐diaryl‐4‐oxo‐4,5,6,7‐tetrahydroindoles, 6‐methyl‐2‐phenyl‐4‐oxo‐4,5,6,7‐tetrahydrobenzofuran and 1‐,6‐dithiaindan‐4‐one. The chemical shifts δ 193–196, δ 195.5 and δ 184 are identified for the carbonyl carbon (C‐4) in the tetrahydroindoles, tetrahydrobenzofuran and dithiaindan derivatives, respectively. These shifts are located in the same region as that reported for the corresponding carbonyl carbon in aryl conjugated ketones. An excellent correlation between the chemical shift for the carbonyl carbon and the chemical reactivity of the ketonic function is noticed in the case of the latter two series of ketones while such a correlation is typically absent in the case o

ISSN:0030-4921    

DOI:10.1002/mrc.1270110910

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractCorrelations with reactivity constants and quantum chemical parameters were used to characterize the substituent effects on the1H NMR spectra of a series ofN,N‐dimethylanilines andN,N‐diethylanilines. The results indicate that the variations of the chemical shifts of the methyl and methylene protons are largely determined by resonance effe

ISSN:0030-4921    

DOI:10.1002/mrc.1270110911

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY