Molecular structure of ethyl nitrate from gas-phase electron diffraction and ab initio MO calculations

Abstract

The molecular geometry of ethyl nitrate has been determined by gas-phase electron diffraction and ab initio MO calculations at the MP2/6-31G* level. There is reasonable general agreement between the experimental and computed structures and also with the rotational constants from a previous microwave study. Both anti and gauche forms are present at 310 K with the anti form prevailing. Computed differences between the parameters of the anti and gauche forms have been assumed from the ab initio results and the following bond lengths ( r g (Å)) and bond angles (deg) obtained for the anti form: CO 1.444±0.004, NO 1.406±0.004, CC 1.520±0.004, NO (mean) 1.208±0.003, CON 113.0±0.6, ONO (anti) 112.2±1.0, ONO (syn) 118.2±0.7, CCO 106.0±1.0. The angles of torsion are φ (anti) 5.4°±3.0° and φ (gauche) 104°±8°; 0° corresponds to the anti form. The nitrogen bond configurations are similar in ethyl nitrate, methyl nitrate and nitric acid.