The pressure dependence of diffusion coefficients of naphthalene in supercritical C02 and naphthalene-¿8 in supercritical ethylene has been measured by using the NMR fixed field gradient spin-echo Bessel function analysis technique. The pressure dependence of the reorientational motion of naphthalene-if8 in C02 and ethylene has been studied by measuring the deuteron spin-lattice relaxation time, 7), as a function of pressure at several isotherms. The temperatures were chosen to cover two regions of the naphthalene-supercritical solvent phase diagram. The experimental data allowed the molecular level test of the applicability of the Stokes-Einstein and Debye equations in the binary systems studied. The expression D(ij/7')0,75 = constant represents the experimental diffusion data well, and the modified Debye equation describes the reorientational motion of naphthalene in supercritical C02 and ethylene solvents.

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The intraand intermolecular contributions to the proton spin-lattice relaxation rate (I/ 'i) for chloroform in toluene were determined as a function of composition in the temperature range between -30.0 and 60.0 °C. The contributions to 1/Ti for the ring protons of toluene were also determined at -10.0, 9.6, and 41.4 °C. A comparison of these various contributions to 1/Ti reveals that the intermolecular interaction between the chloroform proton and the ring protons of toluene is more effective than any other interaction in the chloroform-toluene liquid system. The correlation times for translational motions of chloroform and toluene molecules in the mixtures calculated by using (1/Ti)chci3_r and (1/Ti)r_chci3 are longer than those calculated by using (1/Ti)$$13_chci3 and (1/Ti)r/r, respectively. This result supports the above conclusion.The above results for correlation times and other thermodynamic data suggest that a preferential orientation of the chloroform molecules with respect to the toluene molecules may be postulated to persist, at least for short periods of time (10"10 s, dynamic local structure), in such a manner that the intermolecular interactions between chloroform and the benzene ring of toluene occur more often than the other intermolecular interactions.

The proton nuclear magnetic resonance spectra of a reaction mixture of hydrazine and ethyl acetoacetate (EAA) in aqueous solution under flowing and stopped-flow conditions provides kinetic information concerning the rapid addition step to form the carbinolamine (CA) intermediate and the slower dehydration and cyclization steps to form the anti hydrazone and 3-methylpyrazol-5-one, respectively. The addition step was studied while flowing at rates faster than the dehydration and cyclization rates so that no product signal was observed. Under these conditions, a broad signal resulting from the coalescence of the CH3 proton resonances of EAA and CA is observed. Analysis of the line shape of this broad signal yields the addition rate constant, which has a value that appears to be pH dependent and is of the order of 103 M−1 s−1. Stopped-flow spectra provide the time dependence for the reactant and product signals. Analysis of these time dependences provides information concerning the mechanism of product formation. In contrast with hydroxylamine, CA appears to undergo dehydration and cyclization at comparable rates in the pH range, 8.8–9.2 when hydrazine is the nucleophile. In addition, the anti hydrazone cyclizes at an appreciable rate. These intramolecular cyclization rates are compared with the intermolecular values.