k0dog was just talking about calculating the heat of formation of ketamine and its direct precursor. Presumably he means 1-hydroxycyclopentyl-(o-chlorophenyl)-ketone N-methylimine and ketamine (or maybe he means ketamine hydrochloride and ketamine), but maybe I'm giving him too much credit.
There is a way to calculate the heat of formation of starting material and product, IIRC. Then you can calculate the change of energy... but...
As Rhodium said this doesn't give you activation energies, so it tells you no useful information. Chemistry is more about kinetics (i.e. information about activation energies) than thermodynamics.