摘要:

Abstract45Sc NMR parameters of isomeric ScIIIhexacoordinated complexes ScCl6−nLnn−3formed by the interaction of ScCl3with donor monodentate molecules of trimethyl phosphate, dimethyl sulphoxide, dimethylformamide, dimethylacetamide, formamide, tetramethylurea and Ph3PO in non‐aqueous solutions of CH3CN, CH3NO2, (CH3)2CO, CH3C(O)OC2H5, C4H8O and (C2H5)2O are reported.cis‐ScCl3(TMP)3has been shown to be the preferred species in solvents of low polarity. Increasing polarity of the medium leads to an increase in the relative concentration oftrans‐ScCl3(TMP)3, which has been explained in terms of the different solvation ofcisandtransmolecules owing to the difference in their polarity. The range of45Sc NMR chemical shifts in scandium complexes covers

ISSN:0749-1581    

DOI:10.1002/mrc.1260270202

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

Abstracto‐Benzenediazonium carboxylates couple with methylene‐active compounds to yield hydrazo derivatives with high purity. The1H and13C NMR data of eleven such products are presented and analysed. The predominance of the hydrazo over the azo form is consistent with accepted criteria. Furthermore, evidence for the preference of the carbethoxy group over the acetyl group for intramolecular hydrogen bonding is sugges

ISSN:0749-1581    

DOI:10.1002/mrc.1260270203

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractHigh‐resolution proton nuclear magnetic resonance through heptachlorinated dibenzo‐p‐dioxins are presented. Chemical shifts from dioxins that were synthesized separately are used to assign congeners formed in mixtures. Linear multiple regression analysis was applied to the chemical shift results and the model yielded excellent shift predictability once substituent interactions had been included in the analysis. The average deviation from experimental values was 0.004 ppm. The intra‐ring substituent effects can be explained by a combination of through‐space and ring current effects. Inter‐ring substituent effects showed a dependence on distance, but the reason for this trend is not clear. These measurements demonstrate a reproducible chemical shift effect over

ISSN:0749-1581    

DOI:10.1002/mrc.1260270204

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractBIRD pulses have been shown to provide an effective means of decoupling one‐bond modulation of long‐range response intensity. It is not possible to optimize the BIRD pulse effectively when there is a range of one‐bond coupling constants. To examine the effects of misoptimization of the fixed delays (τ) in the BIRD pulse, the simple alkaloid norharmane was employed. Long‐range heteronuclear correlation spectra were recorded using a modified pulse sequence containing a BIRD pulse midway through the Δ2interval. The experiment was optimized for 10.3 and 11.1 Hz, which correspond to a valley and a peak in the response intensity curve when the experiment is performed without the BIRD pulse midway through Δ2. The delays in the BIRD pulse were variously optimized for values ranging from 80 to 175 Hz. The results suggest that the BIRD pulse is effective in decoupling one‐bond modulations of response intensity even when the τ delays are grossly misoptimized for the one‐bond coupling cons

ISSN:0749-1581    

DOI:10.1002/mrc.1260270205

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

Abstract15N NMR spectra of b−, d−, and e‐cyanocobalamin (vitamin B12) and the products of their amidation with15N‐labeled ammonia show that these analogs are monocarboxylic acids of vitamin B12which result from hydrolysis at the respective propionamide

ISSN:0749-1581    

DOI:10.1002/mrc.1260270206

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractReactions of silver(II) complexes with ketoxime, nitroso and isonitroso compounds in organic solvents were investigated by ESR. The oxidation yielded iminoxy radicals RR′CNO˙ and/or nitroxides R1R2NO˙. The silver(II) complexes with nitrogen ligands (mono‐, bi‐ and tri‐dentate) and AgO were used as oxidizing agents. The reaction products were analysed on the basis of the ESR spectra. The signs of the14N hyperfine constants for the radicals were determined using the ESR spectra in an MBBA liquid nematic crystal as solvent. A linear correlation was found between the hyperfine14N parameters and the Dimroth‐ReichardtET(30) coefficients for the imi

ISSN:0749-1581    

DOI:10.1002/mrc.1260270207

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

Abstract13C chemical shifts are reported for a series of nitro and phenyl derivatives of 2‐ and 3‐methylindoles and 2‐ and 3‐formylindoles, measured in DMSO‐d6. The13C substituent chemical shift (SCS) data are discussed and compared with1H

ISSN:0749-1581    

DOI:10.1002/mrc.1260270208

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractBenzimidazole‐ and benzotriazole‐amino derivatives of prop‐2‐enoic acid were studied by1H NMR spectroscopy in the liquid state and by13C NMR spectroscopy in the liquid and solid states. The spectra shows tautomerism of the benzimidazole and benzotriazole rings,E‐Zisomerism of the double bond of the propenoic acid substituent and the conformation around the amino NHCH bond. The formation of an intramolecular hydrogen bond between the amino proton and the COOR group of propenoic acid is discussed. The structures of the derivatives are presented on the basis of the13C CP‐MAS NMR spectra i

ISSN:0749-1581    

DOI:10.1002/mrc.1260270209

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe C‐13 configurations of several 13‐carboxy‐ and 13‐carbalkoxy‐thiaprotoberbanes were determined and evidence of the solvent dependence of their conformations was provided by1H and13C NMR and DNOE mea

ISSN:0749-1581    

DOI:10.1002/mrc.1260270210

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe selective broadening of13C NMR lines in solutions of piroxicam in polar solvents is related to the equilibrium with its zwitterion by reference to the CP/MAS spectra of the known crystalline solids. The amount of zwitterion inN,N‐dimethylformamide solution at 205 K., in which the interconversion is slow enough to allow the separate spectra to be assigned, is 19

ISSN:0749-1581    

DOI:10.1002/mrc.1260270211

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY