Dynamic 1H NMR Study of the Hindered Internal Rotation in a Particular Biological Phosphorus Ylide Involving 6-Azauracil
Sayyed Mostafa Habibi-Khorassani*1, Mehdi Shahraki1, Malek Taher Maghsoodlou1, Eideh Mofarrah1, Elham Mofarrah2 and Sayyed Rasul Mousavi1

1Department of Chemistry, University of Sistan and Baluchestan, P. O. Box 98135-674, Zahedan, Iran, 2Department of Chemical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran

Abstract: The hindered internal rotations around the partial carbon-carbon double bond (MeO2C=CPPh3), nitrogen-carbon (N-C-CH) and carbon-carbon single (MeO2CH-C-C=PPh3) bonds within dimethyl-2-(6-Aza uracil 1-yl)-3-(triphenylphosphoranylidene) butandioate has been experimentally studied by the dynamic 1H NMR spectroscopic in variable temperatures. The activation (∆H, ∆S, ∆G) and kinetic (kc, Ea.) parameters were calculated in a series of separate dynamic 1H NMR spectra. The energy of activation parameters obtained from classic, Eyring and Arrhenius methods were also compared for carbon-carbon double, this compound. The results from Eyring and Arrhenius plots were in good agreement, however, they were different with the classic method. Rotation around the carbon-carbon single bond ∆G has low value than rotation around the carbon-carbon double bond and rotation around the carbon-carbon single bond.

Keywords: Dynamic 1H NMR; Activations Parameters; Internal Rotations; Ylide; Isomerism

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