Kinetic resolution is a possible method for irreversibly differentiating a pair of enantiomers due to (potentially) different activation energies. While both enantiomers are at the same Gibbs free energy level by definition, and the products of the reaction with both enantiomers are also at equal levels, the , or transition state energy, can differ. In the image below, the R enantiomer has a lower  and would thus react faster than the S enantiomer.
The ideal kinetic resolution is that in which only one enantiomer reacts, i.e. k>>k. The selectivity (s) of a kinetic resolution is related to the rate constants of the reaction of the R and S enantiomers, k and k respectively, by s=k/k, for k>k. This selectivity can also be referred to as the relative rates of reaction. This can be written in terms of the free energy difference between the high- and low-energy transitions states, .
The selectivity can also be expressed in terms of ee of the recovered starting material and conversion (c), if first-order kinetics (in substrate) are assumed.
If it is assumed that the S enantiomer of the starting material racemate will be recovered in excess, it is possible to express the concentrations (mole fractions) of the S and R enantiomers as
where ee is the ee of the starting material. Note that for c=0, which signifies the beginning of the reaction, , where these signify the initial concentrations of the enantiomers. Then, for stoichiometric chiral resolving agent B*,
Note that, if the resolving agent is stoichiometric and achiral, with a chiral catalyst, the [B*] term does not appear. Regardless, with a similar expression for R, we can express s as
If we wish to express this in terms of the enantiomeric excess of the product, ee", we must make use of the fact that, for products R and S from R and S, respectively
From here, we see that
which gives us
which, when we plug into our expression for s derived above, yield
The conversion (c) and selectivity factor (s) can be expressed in terms of starting material and product enantiomeric excesses (ee and ee, respectively) only:
Additionally, the expressions for c and ee can be parametrized to give explicit expressions for C and ee in terms of t. First, solving explicitly for [S] and [R] as functions of t yields
which, plugged into expressions for ee and c, gives
Without loss of generality, we can allow k=1, which gives k=s, simplifying the above expressions. Similarly, an expression for ee″ as a function of t can be derived
Thus, plots of ee and ee″ vs. c can be generated with t as the parameter and different values of s generating different curves, as shown below.
As can be seen, high enantiomeric excesses are much more readily attainable for the unreacted starting material. There is however a tradeoff between ee and conversion, with higher ee (of the recovered substrate) obtained at higher conversion, and therefore lower isolated yield. For example, with a selectivity factor of just 10, 99% ee is possible with approximately 70% conversion, resulting in a yield of about 30%. In contrast, in order to get good ee's and yield of the product, very high selectivity factors are necessary. For example, with a selectivity factor of 10, ee″ above approximately 80% is unattainable, and significantly lower ee″ values are obtained for more realistic conversions. A selectivity in excess of 50 is required for highly enantioenriched product, in reasonable yield.
This is a simplified version of the true kinetics of kinetic resolution. The assumption that the reaction is first order in substrate is limiting, and it is possible that the dependence on substrate may depend on conversion, resulting in a much more complicated picture. As a result, a common approach is to measure and report only yields and ee's, as the formula for k only applies to an idealized kinetic resolution. It is simple to consider an initial substrate-catalyst complex forming, which could negate the first-order kinetics. However, the general conclusions drawn are still helpful to understand the effect of selectivity and conversion on ee.