In this paper, we use quantum chemical methods to characterize the gas-phase nucleophilic addition of methanethiolate, which is typically used as the archetypal nucleophile due to its convenience, to various nitrogen-containing Michael acceptor molecules which are representative of the small-molecule CDK12 inhibitors. We investigate the structural and energetic properties of various enolate rotamers and investigate their electronic properties to determine the most favorable configurations. We also characterize transition states and reaction pathways for enolate formation to understand the associated reaction profiles.