Why is it that if a reaction has a second order rate constant of
anything from 10^7 to 10^12 (s^-1) it is described as
"diffusion controlled"? Surely if collisions can occur at 10^12
then a rate constant of 10^7 can not be diffusion controlled.
Presumably steric factors are invoked: the molecules collide
without reacting. But how can we distinguish steric factors
from the "binding" of the substrate by the enzyme?
How low could a rate constant go and still be diffusion
controlled?
Guy Brown
