To gain further insight into the intrinsic chemical reactivity of the carbamate warhead and the electronic factors that govern the carbamoylation step, we used quantum mechanical (QM) calculations to model the hydrolysis of 6 with a model nucleophile in solution. The investigated model reaction is outlined in Scheme 5: minimal representative structure, i.e., the fragment 6a was used to reduce the size of the system, and methoxide as Ser198 surrogate. At the M06-2X/aug-cc-pVTZ(-f)//M06-2X/6-31G**++ level of theory density functional theory (DFT)predicted Gibbs activation free energy barrier ΔG ‡ was 20.9 kcal/mol. The reaction free energy up to the tetrahedral intermediate 6d was 14.6 kcal/mol, while the corresponding energy for the complete reaction (6a+6b to 6e+6f) was exothermic, -16.4 kcal/mol (Table ). This reaction was modelled in implicit water solution without taking the enzymatic environment into account , which could be better described by QM/MM techniques. Even considering the inaccuracies connected with the DFT method, and that by definition the enzymes lower the reaction barrier, typically by stabilising the transition state, the obtained reaction barrier was found to be in the same range as the experimentally determined Gibbs free energy of activation for 6: 18.5 kcal/mol.