摘要:

AbstractThe carbon‐13 shifts of C‐1, C‐2 and C‐3 are determined in a series of 1‐cyclohexen‐3‐ones substituted in position 1. Linear relationships are demonstrated between the substituent chemical shifts of corresponding carbons in substituted ethylenes, butadienes, α‐enones and benzenes. The substituent chemical shifts of proton H‐2 are also reported and correlated with those of corresponding protons in ethylenes and benzenes. The slopes of the lines for the carbons directly linked to the substituent are close to unity, showing a relative independence of the substituent effect for this nucleus from the variation of the unsaturated framework. In contrast to this, the transmission of the substituent effect through one double bond (nuclei β to the substituents) decreases as the number of conjugated π bonds in the whole structure increases. This relationship is interpreted as being due to the ability of an unsaturated system to spread the variation of π electron density induc

ISSN:0030-4921    

DOI:10.1002/mrc.1270090402

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractL'étude des interactions solvant/soluté des quatre benzothiénopyridines isomères a été entreprise par RMN1H. Le calcul des spectres au second ordre permet de révèler: (i) dans l'acétone une orientation préférentielle des molécules de solvant au niveau du cycle pyridinique; (ii) une forte variation des couplages de la partie benzénique en fonction de la nature du solvant; (iii) une interaction préférentielle du cycle pyridinique dans les complexes de collision du benzène. Ces résultats peuvent ětre transposés aux interactions hétérocycles azotés/bases appariées de

ISSN:0030-4921    

DOI:10.1002/mrc.1270090403

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

Abstract13C FT n.m.r. spectra were obtained from borates of methyl α‐D‐glucopyranoside, triethylboron, sodium tetraphenylboron and 1‐butaneboronic acid employing a simultaneous1H and11B decoupling network. The effectiveness of the system was evident using the three latter organoboron compounds. Since no diminution in line broadening of signals occurred in the spectrum of the sugar borate, the absence of13CO11B coupling was indicated. This finding was confirmed by comparing the effects of varying the temperatures of sugar borates and triethylboron on their conventional13C n.m.

ISSN:0030-4921    

DOI:10.1002/mrc.1270090404

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractCarbon‐13 n.m.r. chemical shifts are reported for diphenyl ether and several of its chlorinated analogs. Carbon shieldings were found to be dependent on the degree of steric interference to conjugative release by the oxygen atom. Substituent effects due to attached chlorine atoms seem to be more easily transmitted into the adjacent aryl moiety if the number oforthochlorines is reduced. These results were clearly seen by a variable‐by‐variable plot display or by using a pattern recognition computer program. Spin‐lattice relaxation times have been measured for several compounds mainly for assignment purposes, but they are also briefly discussed in view of possible interconversion mec

ISSN:0030-4921    

DOI:10.1002/mrc.1270090405

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

Abstract13C n.m.r. studies of a series of tricarbocyclic ring C aromatic diterpenoids using proton‐noise and single‐frequency off‐resonance decoupling, partially relaxed Fourier transform techniques, shift reagents and specifically labelled derivatives have permitted unequivocal assignments of almost all signals. The shieldings caused by oxygenation of C‐18 and C‐19 and by introduction of various substituents in the aromatic ring are discussed. It is concluded that the13C n.m.r. data are sufficiently characteristic to allow stereochemical assignments. Some effects of deuterium substitution on the carbon resonances are

ISSN:0030-4921    

DOI:10.1002/mrc.1270090406

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractAn accurate measurement of the chemical shifts and the coupling constants of some disubstituted acetophenones has been made. The acetophenones studied contained nitro, bromo or amino groups substituted in either the 3,4 or 2,5 positions. For compounds with no substituent adjacent to the acetyl group, the chemical shifts and the coupling constants estimated by the simple additivity of the substituent increments were found to be in reasonable agreement with the experimental values. The two nitro, bromo derivatives substituted in positions 2 and 5 probably prefer the conformer in which the proton H‐6 is adjacent to the acetyl methyl group whilst the 3,4‐disubstituted bromo, nitro and bromo, amino derivatives prefer the conformer in which the H‐6 proton is adjacent to the carbonyl

ISSN:0030-4921    

DOI:10.1002/mrc.1270090407

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

Abstract77Se N.m.r. spectra of 4,4′‐disubstituted diphenyl selenides have been obtained. The chemical shifts could be correlated with substituent constants of the Hammett type or with Swain and Lupton two‐parameter equations. No correlations were observed between these77Se shifts and the13C shifts of the CH2group of 4,4′‐disubstituted diphenylmethanes, the latter shifts showing no correlation with substituent constants. On the other hand linear correlation was observed between the77Se shifts of the 4,4′‐disubstituted diphenyl selenides and the1H shifts of the CH2group of the diphenylmethanes, the13C shifts of their 1‐carbons and the19F shifts of 4‐substitut

ISSN:0030-4921    

DOI:10.1002/mrc.1270090408

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractThe conformations of dihydrolysergamides and 10‐methoxydihydrolysergamides have been inferred from the study of the chemical shifts of the amide hydrogens and their temperature dependence. The13C chemical shifts have been shown to be sensitive to conformational changes of the piperidine ring. The results indicate that the conformation of the latter depends both on the substituent in position 10 and on the solven

ISSN:0030-4921    

DOI:10.1002/mrc.1270090409

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractIt has been found that LAOCOON III can fail to converge for some strongly coupled AA′BB′ spin systems unless trial coupling constants and chemical shifts within a few tenths of a Hz of the real parameters are used to initiate the iteration. This problem seemed linked to those spin systems possessing two or more pairs of energy levels which are nearly degenerate. In the cases where LAOCOON III failed, the program NMRENIT always yielded the correct, converged, iterative solution even with completely arbitrary starting parameters. The latter program also appears to accomplish a given number of iterations with an AA′BB′ system roughly three times as fast as the former

ISSN:0030-4921    

DOI:10.1002/mrc.1270090410

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY

摘要:

AbstractThe configurational and conformational relationship at C‐2 and C‐α in the two racemic diastereomericendo‐α‐methyl‐5‐norbornene‐2‐methanols and the corresponding saturatedendo‐α‐methyl‐2‐norbornanemethanols were determined by first‐order analysis of the1H n.m.r. spectra of these compounds and of their cyclization ether products, i.e. 3‐methyl‐2‐oxatricyclo[4.2.1.04,8]nonanes and 5‐methyl‐4‐oxatricyclo[4.3.0.03,8]nonanes. In addition, the conformational preference of the hydroxyl group in the unsaturated and saturated alcohols was confirmed by the lanthanide induced shift technique, using Eu(fod)3as shift reagent, combined with a computer program involving va

ISSN:0030-4921    

DOI:10.1002/mrc.1270090411

出版商:John Wiley&Sons Limited    

年代:1977

数据来源: WILEY