Scheme for a Unimolecular Reaction Isomerization

With the results thus far obtained we can now make a detailed formulation of a simple chemical reaction, isomerization. Some examples of chemical isomerizations which have been studied in the gas phase and found to follow homogeneous, first-order rates are certain cis-trans isomerizations of olefins and some allylic rearrangements, such as the rearrangement of vinyl allyl ether, CH2=CH—O—CH2—CH=CIl2, to allyl acetaldehyde, CIl2=CH—CH2—CH2—Clio. 

For the general isomerization reaction in which wc admit the possibility of equilibrium we can write the chemical equation 

By A or B we mean any energized molecule of A or B with energy in excess of the critical energy E for the reaction. A is differentiated from B rather arbitrarily in terms of the operational criterion that A is any form of active species which can be formed by activation of A and on de- 

Schematic representation of the potential-energy profile for an isomerization A B. 

In the above scheme we have represented the reaction processes responsible for the production of A and B from A and B, respectively, as collisional processes in which M represents any molecule in the system. The differential equations for the system are 

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