Knowledge Bank

The microwave spectrum of ethyl nitrite, $C2H5ONO$ shows the presence of at least three rotational isomers. Two rotamers correspond to cis-trans $(\tau 1(ON-OC)=0\circ ,\tau 2(NO-CC)=180\circ )$ and cis-gauche $(\tau 1=0\circ ,\tau 2\approx 90\circ )$ structures. Relative intensity measurements show the cis-gauche form to be less stable by $233\pm 50 cm-1$. A moderately strong spectrum of a third rotamer (K = - 0.98) has been assigned a trans-gauche structure $(\tau 1=180\circ \tau 2,\approx 90\circ )$. The spectrum of this rotamer shows no obvious tunneling effects with the other, equivalent guache form. This rigidity contrasts with the very low methyl group barrier in trans methyl nitrite $(V3=30 cal mol-1).1$ Searches for a planar heavy atom trans ethyl nitrite rotamer are currently in progress.