Author: S. BrownsteinPublisher:
ISBN:
Category :
Languages : en
Pages : 15
Book Description
The relaxation behavior of some amides was investigated in their high resolution spectra by the direct saturation-recovery and Overhauser effect methods. The recovery curves and steady-state Overhauser effects were obtained for solutions of dimethylformamide with double- and triple-resonance irradiations. The results were analyzed for 3- and 4-spin systems and the values of relaxation parameters were calculated. It was shown that for dimethylformamide the one-exponential recovery curve approximation gives the T1 values with a precision better than experimental error (plus or minus 2%). The observed difference in relaxation times for methyl group protons was explained by different correlation times and more restricted rotation of 1 of the groups. The correlation times for dipole-dipole interactions of methyl groups with the formyl proton were also evaluated with some reasonable assumptions. The change of the relaxation rate of N-methyl protons in C6H6 and C6D6 solutions was explained by formation of the collision complex with amide molecules and specific intermolecular dipole-dipole proton interaction. This effect could be useful for determination of the cis- and trans-conformations in N-methyl substituted amides and peptides as an absolute method because it does not require measurements on both isomers. (Author).