MOLECULAR-PROPERTIES OF 2-AZIDOETHANOL AND 2-CHLOROETHYL AZIDE - A THEORETICAL-STUDY

Ab initio calculations for 2-azidoethanol (N3CH2CH2OH) and 2-chloroeth yl azide (N3CH2CH2Cl) and for the respective singly ionized structures are reported, Ionization energies based on Koopmans' theorem are in g ood agreement with UV photoelectron spectral measurements. However, ad iabatic energy differences between the singly ionized structures and t he neutral molecules (Delta E values) are very sensitive to the consid eration of electronic correlation effects. The conformational equilibr ium of 2-azidoethanol and 2-chloroethyl azide is very dependent on the quality of the basis set and on the consideration of electronic corre lation effects. For 2-azidoethanol the energy difference between the a nti and gauche conformers, delta(a-g) = E(a) - E(g), is 4.8 kJ mol(-1) at the HF/6-31G level and 0.20 kJ mol(-1) at MP2/6-31G. Further calcu lations using the previous geometry at the MP2/6-31G* level gives -0. 18 kJ mol(-1). These results indicate that the gauche conformer is the most stable and also suggest the possibility of frequent interconvers ions between these two conformers of 2-azidoethanol in the gas phase. For 2-chloroethyl azide the anti-gauche conformational equilibrium is significantly modified when electronic correlation effects are introdu ced into the calculations: delta(a-g) is 0.652 kJ mol(-1) at the HF/63 1G and -0.395 kJ mol(-1) at the MP2/6-31G theoretical levels.