ISSN:0030-4921    

DOI:10.1002/omr.1270210102

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe correlation of the ASIS of the formyl protons of benzaldehyde and six of itsp‐X‐derivatives in 12 aromatic solvents show marked deviations. Evidence is presented that these deviations are caused by variations in the shielding of the internal reference protons caused by aromatic solvents. Equations are developed which gauge the effect of TMS on the linear correlations of proton A

ISSN:0030-4921    

DOI:10.1002/omr.1270210103

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractA method is developed to calculate the intrinsic ASIS of TMS protons used as internal reference, based on linear correlation of the ASIS of a group of sensor protons in two fixed aromatic solvents. Several solute systems (p‐X‐benzaldehydes, camphor, α‐Br‐camphor, 5‐X‐furfurals,p‐X‐acetophenones and methyl ketones) are used to calculate a series of intrinsic ASIS values of TMS in 12 aromatic hydrocarbon solvents. The ΔαTMSvalues are used, in turn, to calculate the intrinsic ASIS of CHO protons in dimethylformamide and diphenylformamide, and of the CH3protons in diethyl ether and

ISSN:0030-4921    

DOI:10.1002/omr.1270210104

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractCarbon‐13 NMR spectra of 56 long‐chain polybranched carboxylic acids their esters, including chloroand acetoxy‐substituted derivatives, have been studied. An empirical linear two‐parameter equation, relating carbon chemical shifts in α‐branched carboxylic acids and their derivatives to the chemical shifts of the corresponding carbon atoms in analogous hydrocarbons, and to the degree of branching at the α‐carbon atom,\documentclass{article}\pagestyle{empty}\begin{document}$$ {\delta_{\rm x} = {\rm A}\delta_{\rm H}+{B_n}+{C}} $$\end{document}is suggested for the assignment of the signals, where δXis the shift in the acid (ester), δHthe shift in its hydrocarbon counterpart andnthe degree of branching. The regression coefficients,A,BandC, are given for X=COOH, COOMe and COOEt.It is shown that with polysubstituted derivatives, the equation may be applied sequentially. The secondary coefficients for the α‐substituent then depend on the nature of the substituent X entering the primary equation. The equation may, if necessary, be applied in combination with the additive and structural increment

ISSN:0030-4921    

DOI:10.1002/omr.1270210105

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractAccurate values ofiJ(HH) andiJ(CH) were obtained for a series of hydroxy‐and mercaptopyridines and‐pyrimidines. It is shown that the3J(CH) values provide a valuable criterion for differentiating aromatic from quinoidal structures, and is an easy method for determiningN‐methylation orN‐additio

ISSN:0030-4921    

DOI:10.1002/omr.1270210106

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractTheperiprotons in a series of 10‐spiroclopropyl‐9,10‐dihydroanthracenes have been shown to have shifts consistent with large (0.43‐0.55 ppm) long‐range shielding effects exerted by neighboring cyclopropyl groups. The shieldings are expected to be sensitive to variations in preferred conformation and, since the range of observed shifts for the five compounds studied is relatively small, it is concluded that all exhibit similar conformational p

ISSN:0030-4921    

DOI:10.1002/omr.1270210107

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractA series ofpara‐ andmeta‐substituted acetophenones were prepared which were highly labeled with18O at the carbonyl function. The natural abundance13C NMR spectra of the compounds were recorded and the18O‐isotope‐induced shifts of the carbonyl carbon were measured in order to determine possible substituent group electronic effects on the18O‐isotope shift. The isotope shifts were found to be correlated with a number of properties which demonstrate the molecular basis of the isotope shift. Good correlations were obtained for the isotope shift as a function of σp+, the carbonyl stretching frequency, the carbonyl group bond order, then→π**transition of the carbonyl group and the chemical shift of theipsocarbon. In contrast, no correlation was observed between the magnitude of the18O‐induced isotope shift and the13C chemical shift of the carbonyl carbon. These properties are discussed in connection with the theoretical basis of th

ISSN:0030-4921    

DOI:10.1002/omr.1270210108

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractCarbon‐13 NMR parameters were determined for some 9‐alkoxy‐ and 9‐alkylthio‐acridines as solutes in DMSO

ISSN:0030-4921    

DOI:10.1002/omr.1270210109

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractA variety of alkaloids have been isolated from the seeds of a range ofErythrinaspecies, including dienoid, alkenoid and lactonic derivatives. The13C NMR spectra of these compounds have been assigned by internal comparisons within this series of related compounds and also by the use of model compounds.

ISSN:0030-4921    

DOI:10.1002/omr.1270210110

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY

摘要:

AbstractThe13C NMR spectra of a number of pyridazine derivatives have been recorded in DMSO‐d6solution and analysed. Examination of the most diagnostic resonances, with particular emphasis on those arising from the pyridazine ring system, enabled the ready establishment of the presence of a ring‐chain tautomerism in 5‐(o‐aminophenylcarbamoyl)pyridazine‐4‐carboxylic acid, methyl 5‐(o‐aminophenylcarbamoyl)pyridazine‐4‐carboxylate, 5‐(o‐aminophenylcarbamoyl)‐3,6,‐dimethylpyridazine‐4‐carboxylic acid and 5‐(2‐amino‐1,2‐dicyanovinylenecarbamoyl)pyridazine‐4‐carboxylic acid. This gave rise to 3′,4′‐dihydro‐3′‐oxospiro[pyridazine‐5(2H),2′(1H)‐quinoxaline]‐4‐carboxylic acid, methyl 3′,4′‐dihydro‐3′oxospiro[pyridazine‐5(2H),2′(1′H)‐quinoxaline]‐4‐carboxylate, 3′,4′‐dihydro‐3′‐oxo‐3,6‐dimethylspiro[pyridazine‐5(2H), 2′(1′H)‐quinoxaline]‐4‐ca

ISSN:0030-4921    

DOI:10.1002/omr.1270210111

出版商:John Wiley&Sons Limited    

年代:1983

数据来源: WILEY