Aziridines and β-lactams are small reactive organic rings bearing a nitrogen atom. Like most three- and four-membered ring compounds, they are characterized by a significant bond angle compression relative to larger rings and open systems. This compression, also known as ring strain, leads to the high reactivity of aziridines and β-lactams, which makes them versatile building blocks in the synthesis of biologically important nitrogen compounds.

Nucleophilic ring opening reactions are the most important reactions that aziridines and β-lactams can undergo. In these reactions, a nucleophile cleaves the ring system, allowing the ring atoms to relax and the ring strain to be relieved. The kinetics, the thermodynamics and the selectivity of this ring opening, however, are highly dependent on the identity of the nucleophile, the substitution pattern of the nitrogen bearing ring and the solvent environment.

In this thesis, molecular modeling will be used to rationalize the effect of structural and environmental parameters on the ring opening of aziridines and β-lactams. Density functional theory (DFT) calculations will be performed on these reactive organic systems in order to compare their energies, structures and other molecular properties like atomic charges and frontier orbitals. This computational effort will gain a better insight into the factors that govern the ring opening and will eventually lead to more efficient syntheses.