Knowledge Bank

Nitroethane contains two internal rotors, a nitro group with a low two-fold barrier and a methyl group with a high three-fold barrier. Its microwave spectrum has been investigated in the 7-40 GHz region. Both conventional Stark spectra as well as microwave-microwave double resonance sepctra have been used to assign relevant parts of the observed spectrum. The general characteristies are typical for a nearly free internal rotor. Calculated predictions from a semi-rigid model have been found to be compatible with a very low barrier value ( $cm-1$) for the internal rotation of the nitro group.