摘要:

AbstractCarbon‐13 NMR spectra of the 17 isomeric methyl hydroxyoctadecanoates and the corresponding acetate derivatives have been measured and chemical shifts assigned to most carbons. Sixteen specifically deuterated hydroxy esters, and their acetates, were employed to make unambiguous assignments from the deuterium isotope effects on the spectra. When substituents are separated from the ends of the chain by 2–3 methylene groups their effects are largely additive. Long range effects of the hydroxyl group were γ, +0.01; δ, −0.09; ε, −0.11; ζ, −0.06; η, −0.05; and θ, −0.04 ppm, and of the acetate group were γ, −0.20; δ, −0.20; ε, −0.16; ζ, −0.11; η, −0.08 and θ, −0.07 ppm, showing that they

ISSN:0030-4921    

DOI:10.1002/mrc.1270110302

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractCarbon‐13 NMR spectra of all the isomers of monomethyl‐, 2,3‐, 2,5‐, 2,6‐, 3,5‐dimethyl‐, 2,3,5‐, 2,3,6‐trimethyl‐ and 2,3,5,6‐tetramethylmorpholine have been obtained at both ambient (25 °C) and low temperature (∼ −100 to −120 °C). The ring carbon shifts appear to be additive with respect to the position of the methyl groups. A good correlation between predicted and experimental shift values was obtained (r= 0.9989). The values were used in an attempt to assign, conformationally, the ‘allcis’ isomer 2,3,5,6‐tetramethylmorpholine, which from1HNMR spin–spin coupling studies has been unsuccessful. Methyl carbon shifts to high field were found for axially oriented carbons. The extracted ‘steric shift’ values for such carbons were compared

ISSN:0030-4921    

DOI:10.1002/mrc.1270110303

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

ISSN:0030-4921    

DOI:10.1002/mrc.1270110304

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractA new method of generation ofN‐acyl‐N‐alkyl nitroxide radicals by photolysis ofN‐nitrosoamides is described. ESR parameters are reported for 17 radicals of the general formula RCON(R′)O.; the high resolution obtained allows conformational analysis which shows a preferredtransconformation around the CON bond and hindered rotation around

ISSN:0030-4921    

DOI:10.1002/mrc.1270110305

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractAnalytical expressions are derived for the analysis of the accuracy of NMR determinations of conformational equilibrium constants,K. The relative error, σK/K, shows a nearly linear increase withKfor two commonly used modifications of the NMR approach to conformational analysis (based on measurements of integral intensities and averaged chemical shifts)

ISSN:0030-4921    

DOI:10.1002/mrc.1270110306

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractThe13C NMR data of six pairs of 18α/18β‐glycyrrhetic acid derivatives are presented. It is shown that the configuration at C‐18 can easily be recognized by inspecting the chemical shifts of several characteristic carbons, e.g. C‐12, C‐13, C‐18 and C‐28. The shifts of these carbons originated by the change of the D/E ring junction proved to be largely independent of the substitution at

ISSN:0030-4921    

DOI:10.1002/mrc.1270110307

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractL'étude des couplages magnétiques à longue distance relevés dans les spectres RMN du proton à 60 MHz d'aziridines du type aza‐7 bicyclo[4.1.0]heptane, permet de préciser la conformation de ces composés et de démontrer sans ambiguïté l'existence de structures bloquées pour certa

ISSN:0030-4921    

DOI:10.1002/mrc.1270110308

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractCarbon‐13 NMR data for 15 substituted 1,2,4‐triazol‐3‐ones are presented and discussed with regard to enolization in the neutral molecules. The coupling constant and chemical shift data show that the proton at N‐2 is not exchanging rapidly in the DMSO‐d6solvent. Using D2OOD−as a solvent, it is found that the C‐3 and C‐5 resonances are shifted downfield by nearly the same amount, suggesting that the proton at N‐4 is being removed. Enolization in the neutral molecules does not occur to a

ISSN:0030-4921    

DOI:10.1002/mrc.1270110309

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractThe13C spectra of a series of thyroid hormones and derivatives including thyroxine (T4) sodium salt, T4‐N‐acetyl methyl ester, triiodothyronine (T3), T3‐sodium salt, T3‐methyl ester hydrochloride, sodium triiodothyroacetate and ethyl triiodothyropropionate were assigned using chemical shift trends from model compounds, coupling constants and relaxation times. The13C spectra of a series of diphenyl ethers were assigned and the chemical shift trends observed were analyzed on the basis of conformational changes engendered by mesomeric or steric

ISSN:0030-4921    

DOI:10.1002/mrc.1270110310

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY

摘要:

AbstractLes mesures des déplacements chimiques de29Si dans les silacyclopentènes vérifient les conclusions obtenues par RMN de1H et1

ISSN:0030-4921    

DOI:10.1002/mrc.1270110311

出版商:John Wiley&Sons Limited    

年代:1978

数据来源: WILEY