Isotope Effects on theO,H Coupling Constant and theO–{H} Nuclear Overhauser Effect in Water |
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| Authors: | Nickolai M Sergeyev Natalia D Sergeyeva William T Raynes |
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| Institution: | a Department of Chemistry, Moscow State University, 119899, Moscow, Russia;b Russian Peoples' Friendship University, 117198, Moscow, Russia;c Department of Chemistry, University of Sheffield, Sheffield, S3 7HF, United Kingdom |
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| Abstract: | The NMR spectra of solutions of 30%17O-enriched H2O and D2O in nitromethane display the resonances of the three isotopomers H2O, HDO, and D2O. All17O,1H and17O,2H coupling constants and the primary and secondary isotope effects onJ(17O,1H) have been determined. The primary effect is −1.0 ± 0.2 Hz and the secondary effect is −0.07 ± 0.04 Hz. Using integrated intensities in the17O NMR spectra, the equilibrium constant for the reaction H2O + D2O 2HDO is found to be 3.68 ± 0.2 at 343 K. From the relative integrated intensities of proton-coupled and -decoupled spectra the17O–{1H} NOE is estimated for the first time, resulting in values of 0.908 and 0.945 for H2O and HDO, respectively. This means that dipole–dipole interactions contribute about 2.5% to the overall17O relaxation rate in H2O dissolved in nitromethane. |
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| Keywords: | isotope effects on coupling constants NOE17O– { 1H} |
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