摘要:

AbstractThe calculated12C,13C and77Se spectra of selenophene have been reproduced from the observed proton NMR spectrum in the orienting medium Merck ZLI 1167, and the entire ring structure computed. The effects on structure of vibration, solvent dependence of couplings and temperature have been explored. Most notable was the observation of a substantial increase in the SeC bond length, comparable to that previously reported for selenophene in Merck Phase I

ISSN:0030-4921    

DOI:10.1002/mrc.1270190402

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractApplication of the lanthanide shift reagent Eu(fod)3to a series of benzylideneanilines causes isomerization of the stabletransform to the less stablecisform. A linear relationship was obtained between the %cisisomer with the mole ratio of Eu(fod)3/substrate.

ISSN:0030-4921    

DOI:10.1002/mrc.1270190403

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe spectra of several 2‐methyl‐6‐R‐disubstituted naphthalenes (R=H, Me, I, NO2, Cl, SO2Cl, OH, OMe, COMe, Br, F and NHCOMe), have been analysed. Chemical shift and coupling constant values of these compounds are presented. The proton chemical shifts have been found to correlate with theorthoparam

ISSN:0030-4921    

DOI:10.1002/mrc.1270190404

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractCarbon‐13 and proton NMR spectra are reported for phenyl‐,4‐methoxyphenyl‐, 4‐ethoxyphenyl‐ and 3‐methyl‐4‐methoxyphenyltellurium tris(diethyldithiocarbamate). Both the1H and the13C spectra are typical of compounds undergoing a fast exchange process, only theN‐methylene proton signals and the thiocarbonyl carbon signals showing evidence for exchange broadening. The phenyl C‐1 carbon signal is deshielded relative to benzene (by 12.0 ppm), and shows solvent dependence. The thiocarbonyl carbon atoms absorb at 197.5‐199.1 ppm, showing solvent dependence but little sensitivity to the

ISSN:0030-4921    

DOI:10.1002/mrc.1270190405

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe13C NMR spectra of several 2‐substituted imidazoles and benzimidazoles have been measured. The substituent was CH3, COOH and CONHR, where R = H,n‐Bu,p‐tolyl orm‐chlorophenyl. Carbons 4 and 5 in the imidazoles and the carbon pairs 8/9, 4/7 and 5/6 become equivalent by proton transfer from N‐1 to N‐3, possibly through intermolecular association. The rate of this proton exchange increases with concentration and temperature. It decreases with extension of the 2‐substituent (rate CH3≫CONH‐phenyl>CONH‐p‐tolyl ≃ CONH‐m‐chlorophenyl ≫ CONH‐n‐butyl) due to steric hindrance at the sit

ISSN:0030-4921    

DOI:10.1002/mrc.1270190406

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractA quantitative measure,πΔ, for expressing the π‐deficiency and π‐excessiveness of heteroaromatic compounds has been developed through13C NMR chemical shift studies. An example which correlates electrophilic reactivity in π‐excessive systems withπΔ of these compounds is given. The following decreasing order of π‐excessiveness and increasing π‐deficiency of a number of heteroaromatic systems has been established (numbers in parentheses correspond toπΔ): tellurophene (1.83), selenophene (1.43), thiophene (1.35), furan (1.31), benzene (1.00), pyrazine (1.00) pyridine (0.89), pyrimidine (0.77), pyridazine (0.71), 1,2,4‐triazine (0.64). These correlations also allow the prediction of13C chemical shifts in substituted heteroaromatic compounds, where the ratio of the difference between a given substituted heterocyclic compound and its parent, and the identically substituted benzene derivativ

ISSN:0030-4921    

DOI:10.1002/mrc.1270190407

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractCarbon‐13 chemical shifts are reported for 16para‐substituted phenyl isothiocyanates measured at 1 and 10 mol % in chloroform‐dsolution. Data for the NCS group were not obtained at 1 mol %, but concentration effects for the other resonances were negligible. Hammett, dual substituent parameter (DSP) and DSP‐nonlinear resonance (DSP‐NLR) analyses were used to evaluate substituent effects on the substituent chemical shifts (SCS) for theipso‐carbon (C‐1), C‐2, and the NCS carbon atoms. A good Hammett correlation was observed for C‐1 (νp+= 8.1 ppm,r= 0.98 at 1 mol %) but was improved for the higher order correlations with the following results, DSP:ρI= 5.4, ρR° = 22.2,r= 0.998; DSP‐NLR: ρI= 5.6, ρR° = 20.5, ϵ = −0.22,r= 0.999. The 10 mol % data were very similar except the value of ϵ was −0.26 and confirms the phenyl‐bonded NCS moiety as a mild electron acceptor substituent. Hammett correlations were unsuccessful for the C‐2 data, but fairly good results were obtained from the higher order analyses. For the 1 mol % data, DSP: νI= 1.6, νR° = −2.0,r= 0.976; DSP‐NLR: νI= 1.8, νR° = −2.6, ϵ = 1.1,r= 0.982. Excellent correlations were obtained for the 10 mol % NCS carbon data. Hammett: νp° = 6.2,r= 0.997; DSP: νI= 5.9, νR° = 7.0,r= 0.997; DSP‐NLR: νI= 5.8, νR° = 7.6, ϵ = 0.25,r= 0.997. The positive ν values in these three correlations contrast the negative values usually observed for carbonyl and thiocarbonyl carbons, and more closely parallel results previously reported for the β

ISSN:0030-4921    

DOI:10.1002/mrc.1270190408

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe preparation, isolation and characterization by proton and13C NMR of the four possible atropisomers ofmeso‐tetra(2‐methoxy‐1‐naphthyl)porphyrin is described. Chemical shift differences due to atropisomerization effects are observed in the porphyrin and naphthyl rings. Comparison of the naphthyl chemical shifts with those of the model compound 1‐isopropenyl‐2‐methoxynaphthalene allows the shifts due to the porphyrin ring current to be isolated. The observed Δδ values of the naphthyl protons agree well with those calculated from the previously described porphyrin ring current model, and allow both the angle of tilt of the naphthyl ring and the dihedral angle of the 2‐methoxy substituent to be estimated. In contrast, the Δδ values for the naphthyl carbons bear no relationship to the calculated ring current shifts. Calculations of the total ring current contribution (porphyrin plus naphthyl rings) at the different naphthyl rings of the unsymmetric type III isomer show that at least part of the observed atropisomerism effects are due to the long‐range current shifts of the naphthyl rings. The results also provide a clear demonstration of the identity of the porphyrin ring current in the free base a

ISSN:0030-4921    

DOI:10.1002/mrc.1270190409

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe high field proton NMR spectra (500 and 600 MHz) of the peptide hormone somatostatin in D2O are reported. The results obtained are used to derive values of the couplings and chemical shifts related to the solution conformation of several of the side chains. This work resolves a discrepancy in the literature concerning the assignments of resonances in the spectrum. It also provides a means of testing the accuracy of obtaining values for these couplings and shifts in previous 2D NMR studies at lower field from strongly coupled multiplets in spectra of this complexity.

ISSN:0030-4921    

DOI:10.1002/mrc.1270190410

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe results of some SCPT and SOS calculations of1J(CH),1J(FC),2J(FH),3J(FH),3J(FF) and1J(CC) in a variety of solvents are reported. The calculations employ the solvaton model and INDO parameters. In almost all cases the coupling is predicted to increase as the dielectric constant of the solvent increases, the exception being3J(FH)cisin trifluoroethylene which is supported by experimental results.

ISSN:0030-4921    

DOI:10.1002/mrc.1270190411

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY