摘要:

AbstractThe molecular dynamics and the association of 2‐pyrrolidone, δ‐valerolactam and ϵ‐caprolactam in H2O and CCI4solutions have been investigated by13C nuclear magnetic relaxation. With the aim of unambiguously establishing13C assignments the following parameters have been measured: carbon chemical shifts, one‐bond carbon–proton coupling constants and one bond carbon–carbon coupling constants. In the particular case of 2‐pyrrolidone, the13C relaxation times do not provide enough information in order to study in detail the dynamics of the molecule.15N Relaxation for the neat liquid has proved to be a valuable complement for totally analysing the anisotropic motion

ISSN:0030-4921    

DOI:10.1002/mrc.1270190102

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe rate constants of intramolecular processes can sometimes be measured only in the presence of optically active auxiliary compounds. The problem of obtaining the rate for the free molecule was solved by linear extrapolation of rate constant from the complexed to the uncomplexed molecule (LERCUM). This method is developed theoretically and checked experimentally. 2‐Bromo‐2‐methyl‐1‐(3‐bromo‐2‐methoxy‐4,5,6‐trimethylphenyl)‐1‐propanone has the advantage that rotation about its carhonyl‐to‐aryl bond can be measured both in the presence of (+)−2,2,2‐trifluoro‐1‐phenylethanol as well as in the absence of an auxiliary compound. The novel method of extrapolation is confirmed by

ISSN:0030-4921    

DOI:10.1002/mrc.1270190103

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe13C NMR chemical shifts of nine acetoxyxanthones are reported and identified. The acetoxy substituent effects have been evaluated and the corresponding shift increments proposed.

ISSN:0030-4921    

DOI:10.1002/mrc.1270190104

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractHigh resolution1H NMR is applied to the study of hydrolysis and equilibria in the complex system of γ‐[1‐methyl‐5‐bis(β‐chloroethyl)amino‐2‐benzimidazolyl]butyric acid and D2O. Kinetic data for the individual hydrolytic steps are obtained for the first time. The hydrolytic reactions are pseudo first order. The differences in the activation energies of the two hydrolysis steps are accounted for by different intermediates. Furthermore, equilibrium constants for the deuteration of the N mustard group in the individual products are quantitatively estimated. They show an increase of the basicity of N mustard with hydrolysis. The applicability of the1H NMR method is restricted to a pD

ISSN:0030-4921    

DOI:10.1002/mrc.1270190105

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractComparison of the room and low temperature (203 K)13C NMR spectra of 3‐cis‐bicyclo[4.4.0]decanone and its 2,2,4,4‐tetradeuterio isotopomer provides information about the deuterium isotope effect on the conformational equilibrium in this compound. Four‐bond low field deuterium isotope effects on some carbon chemical shifts are observed. These effects can be used for unambiguous assignment of the13C lines to carbon atoms in alicyclic co

ISSN:0030-4921    

DOI:10.1002/mrc.1270190106

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractAn analysis of the1H and13C spectra of 1‐azafluorene has been carried out using computer calculations and homo‐ and heteronuclear double resonance techniques. The4J,5Jand6Jlong‐range coupling constants of the 9‐CH2group protons with the protons of the pyridine and the phenylene rings have been observed and measured. The long‐rangeJ(CH) values in the1H coupled13C spectrum have been assigned and measured on a first‐

ISSN:0030-4921    

DOI:10.1002/mrc.1270190107

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractCharacteristic13Cchemical shift ranges and substituent shifts of heterocyclic ring carbon atoms have been identified for a number of 1‐aryl‐3‐phenyl‐2‐thioxo‐4‐imidazolidinones.13CNMR spectra may be used to detect slow internal rotation about the aryl CN‐1 bond in compounds with diastereomeric rotational isomers; many corresponding carbon atoms in the rotamers have distinctly different chemical shifts. The δ‐effects originating from arylorthosubstituents are both electronic

ISSN:0030-4921    

DOI:10.1002/mrc.1270190108

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe13C NMR spectra of the antileukemic ansa macrolide maytansine and eight naturally occurring homologues were recorded. Signals were assigned to specific carbon atoms of the ansa macrolide ring and C‐3 ester side chain using data from off‐resonance decoupling, single frequency decoupling, and 180°–τ–907° double pulse experiments. The assignment of each carbon is discussed for maytansine and tabulated for the other eight may

ISSN:0030-4921    

DOI:10.1002/mrc.1270190109

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe proton NMR spectra of 2,3,4,4‐tetramethyl‐3‐t‐butylpent‐1‐ene rotarners have been completely assigned by low temperature NOE measurements. Chemical shifts andcisandtransallylic coupling constants are unambiguously determined. It is shown that other 2‐substituted propenes can be assigned on the basis of the coupling constants, but not from the chemical shift data. In 1,2‐disubstituited propenes, however, the transoid coupling constant falls in the range of the cisoid coupling constant values of the 2‐substituted propenes. Coupling constants cannot, therefore, be used in the 1,2‐disubstituted propene series as a criterion for de

ISSN:0030-4921    

DOI:10.1002/mrc.1270190110

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY

摘要:

AbstractThe NMR chemical shift method was applied for the determination of the magnetic susceptibility of paramagnetic transition metal complexes in solution. The method was found to be very useful for the determination of magnetic susceptibility changes during a chemical reaction in which one paramagnetic compound produced another. The concentrations of two paramagnetic cobalt complexes [Co3O(O2CCH3)6(HO2CCH3)3] and Co(O2CCH3)2, were calculated from the chemical shift value observed during their reaction with cumene hydroperoxide. The results are consistent with those obtained from electronic spectra.

ISSN:0030-4921    

DOI:10.1002/mrc.1270190111

出版商:John Wiley&Sons Limited    

年代:1982

数据来源: WILEY