PROTON AND DEUTERON SPIN-LATTICE RELAXATION IN n-DODECANE.
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Date
1968
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
The spin-lattice relaxation rates of protonated and deuterated n-dodecane are measured neat and in solutions of benzene, carbon tetrachloride and carbon disulfide. An isotopic dilution technique provides a means of evaluating the intramolecular relaxation of protonated n-dodecane. It was found that the ratio of the deuteron to proton intramolecular relaxation rates is approximately 8.5 for the solutions studied. The observed molecular motions are to a first approximation consistent with the Stokes-Einstein hydrodynamic $model^{1}$ corrected for the particulate nature of the solvent by a microviscosity $coefficient.^{2}$ For pure n-dodecane and n-dodecane in carbon tetrachloride the temperature dependence of the relaxation rate is the same as the temperature dependence of the viscosity divided by the absolute temperature. In pure deuterated n-dodecane n-dodecane the activation energy obtained by the spinlattice relaxation measurements is $4,066 \pm 0.009$ kcal mole$^{-1}$ in the temperature range from $264^{\circ} K$ to $295^{\circ} K$ and $3.515 \pm 0.015$ kcal mole$^{-1}$ between $295^{\circ} K$ and $370^{\circ} K$. In the temperature range between $264^{\circ} K$ and $297^{\circ} K$ the activation energy of n-$C_{12}H_{26}$ is $3.76 \pm 0.04$ kcal mole$^{-1}$. From $297^{\circ} K$ to $373^{\circ} K$ this energy is $3.64 \pm 0.04$ kcal mole$^{-1}$. In a solution of 25% n-dodecane and 75\% carbon tetrachloride by volume, the activation energies of the deuterated and protonated compounds are essentially the same. Between $264^{\circ} K$ and $348^{\circ} K$ they are observed to be approximately 3.1 kcal mole$^{-1}$.
Description
$^{1}$ N. Bloembergen, E.M. Purcell, and R.V. Pound, Phys. Rev. 7***, 369 (1948). $^{2}$ A. Gierer and K. Wirtz, Z. Naturforsch. 8a, 532 (1953).
Author Institution: Field Research Laboratory, Mobil Research and Development Corporation
Author Institution: Field Research Laboratory, Mobil Research and Development Corporation