摘要:

AbstractThe13NMR signals of camphene (1) and α‐pinene (2) are reassigned unequivocally.J(CH) values of 1, 2, bornene, norbornene and norbornadiene are report

ISSN:0030-4921    

DOI:10.1002/mrc.1270200402

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe phenoxy radicals obtained from 2,2′‐ and 4,4′‐biphenyldiols show, in nonpolar solvents, symmetrization of the unpaired electron spin density on the two phenyl rings in the temperature range 290–410 K. Below 270 K the paramagnetic systems became diamagnetic. This para‐diamagnetic conversion with temperature is reversible. According to INDO calculations the symmetrization of spin density is due to the formation of dimeric phenoxy radicals. The para‐diamagnetic conversion at various temperatures is explained by the reversible conversion of the radical dimer to the quinone‐hy

ISSN:0030-4921    

DOI:10.1002/mrc.1270200403

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe influence of substituents on the13C NMR chemical shifts of 2‐substituted 1‐methylbenzimidazoles has been investigated. The electronic effects of the substituents are transmitted to C‐4 and C‐7 mainly by the resonance mechanism, and to C‐5, C‐6 andN‐CH3, by approximately equal contributions of the resonance and inductive components. A critical analysis of the share in the transmission of substituent effects through the ‘pyridine‐type’ and ‘pyrrole‐type

ISSN:0030-4921    

DOI:10.1002/mrc.1270200404

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe radical anions ofm‐ andp‐ nitro‐substituted derivatives of several classes ofN‐(thioacyl)‐piperidines and ‐morpholines have been studied by ESR spectroscopy. The anion radicals were found to be centred on the nitro group, and the distribution of the unpaired electron was found to be dependent on the extent of conjugation between the thiocarbonyl group and the aromatic moiety of the molecule. The hfs constants were discussed in terms of the spin densities calculated by the McLachla

ISSN:0030-4921    

DOI:10.1002/mrc.1270200405

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

Abstract13C NMR spectra for a number of furanoflavones are presented and analysed. The effects of various substituents are discussed.

ISSN:0030-4921    

DOI:10.1002/mrc.1270200406

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractSome calculations of1J(SiC) and1J(SiF) are performed by self‐consistent perturbation theory employing standard INDO parameters.1J(SiC) is dominated by the contact interaction, whereas the opposite sign for1J(SiF) is due to a large orbital interaction. The1J(SiC) data are satisfactorily reproduced by calculations employing an sp basis set, whereas the inclusion of silicon 3d orbitals provides a more reasonable account of1J(SiF

ISSN:0030-4921    

DOI:10.1002/mrc.1270200407

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractSeveral 6‐methyl‐9‐carbamoyltetrahydro‐4H‐pyrido[1,2‐α]pyrimidin‐4‐ones have been prepared using phosgene iminium chloride. These compounds can exist in equilibrium as thecis(3A) imine ⇌ (3B) enamine ⇌trans(3C) imine.1H,13C and15N NMR prove that thecis‐ andtrans‐imine isomers are predominant in the equilibrium.1H NMR data reveal that the share of the 3B enamine form is negligible at measurable concentrations. The isomeric ratio 3A:3C is time dependent and can be monitored by measuring the CH3C‐6 and (CH3)2N signals. The13C NMR data show that doublets in the range 42–45 ppm for C‐9 are only compatible with the imine forms 3A and 3C. The SCS values of the CH3C‐6 and OCN(CH3)2groups were calculated and used for identification of thecisandtransisomers.15N NMR data show that the N‐1 chemical shift of the imine is approximately − 140 ppm for compound 3, whereas that of a fixed enamine is around − 267.8. This provides additional support for the predominance of the imine tautomers in the equilibrium 3A ⇌ 3B ⇌ 3C.15N data allow t

ISSN:0030-4921    

DOI:10.1002/mrc.1270200408

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe15N NMR spectra of several substances with nitrogen—nitrogen bonds have been obtained at the natural‐abundance level by high‐resolution NMR spectroscopy. Azo (NN) nitrogens are 300–500 ppm deshielded compared with hydrazo (NHNH) nitrogens. The sensitivity of the15N shifts in these types of substances to substituent changes are reported, along with15N–1H spin–spin couplings for some hydrazo compounds. Hydrogen‐bonding effects arising from solvent changes on the15N shifts of azoxybenzene are different for its two kinds of nitrogen. The15N NMR spectrum ofN,N'‐dinitrosopiperazine in dimethyl sulfoxide at room temperature is consistent with the presence of two different conform

ISSN:0030-4921    

DOI:10.1002/mrc.1270200409

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe 270 MHz NMR data ontrans‐ andcis‐(H‐4a, H‐7)‐7‐ethylperhydropyrido[1,2‐c][1,3]thiazine show heavy conformational bias to thetrans‐ andS‐insidecis‐fused conformations, respectively. Comparison of the13C NMR spectra of these anancomeric systems with the13C NMR spectrum of perhydropyrido[1,2‐c][1,3]thiazine indicates atrans‐⇌S‐insidecis‐conformational equilibrium for the latter compound in CDCl3at 25°C, containingca75%trans‐fused conformer. The13C NMR spectrum of perhydropyrido[1,2‐c][1,3]‐thiazine at −75°C showed 64%trans‐fus

ISSN:0030-4921    

DOI:10.1002/mrc.1270200410

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe positions of conformational equilibria in 1,5‐, 1‐6‐ and 1,8‐dimethylperhydro‐oxazolo[3,4‐a]pyridines were determined by1H NMR spectroscopy. Thecis‐(H‐5, H‐8a)‐1,6‐dimethyl‐perhydro‐oxazolo[3,4‐a]pyridine. In contrast,r‐1,t‐6,t‐8a‐1,6‐dimethylperhydro‐oxazolo[3,4‐a]pyridine preferred thecis‐fused conformation. Three of the 1,8‐dimethylperhydro‐oxazolo[3,4‐a]pyridines adopted thetrans‐fused conformations (with distortion of the system in the case of ther‐1,c‐8,c‐8a derivative) and ther‐1,c‐8,t

ISSN:0030-4921    

DOI:10.1002/mrc.1270200411

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY