Diffusion control of homogeneous reactions

upon encounter, the reaction rate is much slower than the rate to bring the species together, then the reaction is not controlled by encounter. If the two rates are comparable, then the reaction is partially controlled by encounter (or diffusion). 

For a fuUy diffusion-controlled (or encounter-controlled) reaction. 

Three reactions are discussed below. Consider Reaction 2-lOb  

All reactions in aqueous solutions should have rate constants smaller than that calculated from fully diffusion-controlled reactions because diffusion must play a role and the reaction rate may not be faster than the rate to bring the reactants together. 

Using Equations (2-60) and (2-57) for kf and K, expressions (which are newer versions and differ slightly from the expressions used by Ganguly and Tazzoli, 1994), and letting I = (3.692 + O.lXps) A (the average distance between the centers of Ml and M2 sites along c and b directions), then it can be found that 

---