The velocity coefficient for bimolecular reactions in solution

Abstract

In a letter under the above title in NATURE of May 12, the interchange of energy between solvent and dissolved reactant molecules is discussed. This matter was considered in a paper entitled "The Benzylation of Amines: Part 3," in the Journal of Physical Chemistry, 673; 1926. If activated molecules of solute are deactivated by collision with solvent molecules, the latter molecules may either acquire a higher velocity, or be themselves activated, or radiation may be emitted, for the energy absorbed from the activated solute must go somewhere. The molecules of the solvent cannot acquire a higher velocity unless the temperature of the solution rises. I do not know whether there is any experimental evidence in support of this; what it amounts to in a simple case appears to be that if we isolate two vessels, one containing, say, benzene, and the other a solution of a reacting substance such as benzyl bromide in benzene, then the temperature of the latter should rise. If the reply is that unactivated molecules of the reactant absorb this energy of translation of the solute molecules, then the position is as suggested by Mr. Louis Kassel (NATURE, May 12), namely, that the effect of the third molecule, the solvent, should probably be as often activational as deactivational.