Showing papers by "Henry Eyring published in 1940"

Calculation of Dipole Moments from Rates of Nitration of Substituted Benzenes and Its Significance for Organic Chemistry

Abstract: (1) From a set of assumptions which seem reasonable a priori, the authors calculate the charge distributions in the molecules of mono‐substituted benzenes, and the dipole moments of the latter from reaction rate data alone. These coincide very well with the observed moments. (2) From the dipole moments of aromatic and aliphatic compounds, the ortho‐, meta‐ and para‐percentages during nitration were calculated. These also accord satisfactorily with the experimental values. (3) It is concluded that these two facts give a quantitative basis to the usual explanation about the orienting power of substituents of benzene. (4) The nitration of benzene is an ionic reaction : The nitrating agent X·NO2 dissociates into X— and NO2+ in the activated complex, and the latter ion interacts with the reacting carbon. The activation free energy is reduced by the amount of the electrostatic interaction, i.e., 4.80·10—10ey/(rD). Here ey is the charge on the reacting carbon, r, the distance between NO2+ and the reacting carbon...

Pressure and Temperature Effects on the Viscosity of Liquids

Abstract: The free energy of activation for viscous flow is related to an entropy and energy of activation by the same equations as any equilibrium. This, for the theory of viscosity is perfectly general and independent of the mechanism. The rolling over each other of pairs of molecules lying in adjoining layers is the mechanism which appears to be the most probable, and the equations for this bimolecular flow process are developed here. At low pressures the heat of activation for viscous flow is about one‐third the energy of vaporization, but as the pressure is raised, it increases rapidly because of the work term, P V/n′. Here P is the external pressure,V is molal volume and V/n′ is the extra volume required before the flow process can take place. Calculations made for n‐pentane, ether, benzene, iso‐pentane, water, and mercury over as extended a temperature and pressure range as the data permit are found to agree satisfactorily with the experimental viscosity. The results are interpreted in terms of the liquid structure and the mechanism of viscous flow. The results of applying our theory to the liquids for which the necessary data is available show that the effect of pressure on viscosity can be calculated a priori, with thermodynamic data only, with reasonable success.