摘要:

AbstractThe molar specific heat of NaBrO3in the temperature range 4.2–336 K was determined experimentally and compared with the theory developed by Stahl and generalized in this paper. The relationship between the molar specific heat and temperature was explicitly studied and compared with results obtained by other workers. The method developed also produces the Debye temperature, Θ the maximum angular frequency, omega;m, and the productIωt2of the BrO3group, where I is the moment of inertia and ωl, is the lattice vibration. The relationships between the79Br NQR frequency and temperature and between the NQR frequency and molar specific heat were obta

ISSN:0749-1581    

DOI:10.1002/mrc.1260280202

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractPlatinum‐195 chemical shift measurements forcis‐PtCl2(PCy3)2andtrans‐PtXCl(PCy3)2(X = H, Cl, SnCl2Ph and SnCl3) in methylene chloride solution are reported. A comparison of these shifts with those from analogous complexes containing less bulky phosphine ligands indicates significant steric effects on the195Pt shift of the PCy3complexes. Forcis‐PtCl2(PCy3)2a downfleld shift of over 200 ppm is obtained. For thecis‐PtCl2(PCy3)2complexes the deshielding of195Pt is found to increase in the order X = H

ISSN:0749-1581    

DOI:10.1002/mrc.1260280203

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe Conformations and dynamics of 1‐anilinonaphthalene‐8‐(ANS) in solutions of solvents with different polarities and hydrogen‐bonding properties were investigated by high‐resolution1H and13C NMR spectroscopy. Two‐dimensional correlated spectrocopy, tirations with paramagnetic ions and one‐dimensional spin‐decoupling techniques were employed t assign the spectra observed from both nuclei. Nuclear Overhauser effect data provided evidence that the fluorohore adopts compact conformations in the more pola solvents.13C spin‐lattice relaxation times indicated that the benzene ring of ANS has a degree of internal mobility in the solutions of all the solvents studied. Measurement of Stokes shifts in different solvents that the special fluorescence properties of ANS in aqueous solutions arise from the proton donor character of the solvent rather than from its polarity or the conformational flexibility o

ISSN:0749-1581    

DOI:10.1002/mrc.1260280204

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

Abstract1H and13C NMR chemical shift data and3J(H,H) values can be used to predict the conformational blend of new members of a series of erythromycin A derivatives in CDCI3solution.

ISSN:0749-1581    

DOI:10.1002/mrc.1260280205

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe high‐resolution13C solid‐state NMR spectra of naphthazarin polymorphs and some of its derivatives having methyl substituents are discussed. Differences observed between the spectra of the A and B forms and that of the C modification of naphthazarin are explained by invoking hydrogen‐bonding effects. The 2‐methyl and 2,3‐dimethyl derivatives show spectra consistent with their x‐ray‐determined structure as being mainly composed of the tautomer bearing the substituents on the quinonoid ring. The 2,7‐dimethyl‐substituted compound undergoes a fast intramolecular proton migration at room temperature between tautomers present in nea

ISSN:0749-1581    

DOI:10.1002/mrc.1260280206

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractTwo sesquiterpenoids, spatulenol and (−)‐caryophyllene oxide, were isolated from the hexane extract of the Brazilian plantVernonia mollissimaDon. The1H and13C NMR spectra of these compounds have been reassigned completely by COSY experiments and13C/1H shift correlation diagr

ISSN:0749-1581    

DOI:10.1002/mrc.1260280207

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractA computer program has been developed which can calculate the time dependence of individual proton magnetizations in a protein, for a variety of relaxation measurements in solution, using non‐selective and selective excitation pulses. The basic design and capability of the program are described, together with its limitations. The program is used to simulate proton relaxation experiments by non‐selective and selective excitation, and to simulate spin diffusion in a typical globular proteinStreptomycessubtilisin inhibitor (SSI). The mechanism of selective spin diffusion in SSI is discussed based on a comparison of the calculated results with results of cross‐saturation experi

ISSN:0749-1581    

DOI:10.1002/mrc.1260280208

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe effects of one‐bond and two‐bond2H,13CO and C18O isotope shifts on51V shielding in various carbonyl–Cp–vanadium complexes (Cp = n5‐cyclopentadienyl) are reported and discussed with respect to the sensitivity of51V shifts to bond extensions, and the rovibrationally averaged values of such bond extensions. These isotope effects provide some insight into the bonding situation in these complexes. It is shown that the rate‐determining step in the reaction between V(CO)6and C5H5D, which leads to CpV(CO)4, isnotsubject to a kinetic isotope effect. The deuterium solvent isotope effects on51V shielding in [V(CO)6]‐ and [VO4]3‐are al

ISSN:0749-1581    

DOI:10.1002/mrc.1260280209

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractThe109Ag NMR spectrum of [Ag(Ph2PCHCHPPh2)2]NO3, a complex with antimicrobial and antitumour activity, was obtained using a retro‐INEPT two‐dimensional31P–{109Ag} pulse sequence. This allowed the measurement of the31P and109Ag chemical shifts and the1J(109Ag,31P) coupling constant in a single 2 h experiment and offered a considerable signal‐to‐noise gain compared with109Ag–{31P} INEPT

ISSN:0749-1581    

DOI:10.1002/mrc.1260280210

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractOne‐dimensional selective scalar transfer experiments are presented for the analysis of13C NMR data for multilabelled molecules. ‘Classical’13C COSY experiments rapidly show limitations when a complete determination of remote coupling constants is required. Conversely, combination of 1D COSY and RELAY affords all the required information very rapidly and accurately. Three13C‐labelled monosaccharides exhibiting different degrees of spectral complexity are used to illustrate the merits of these tec

ISSN:0749-1581    

DOI:10.1002/mrc.1260280211

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY