Steric asymmetry in electron transfer from potassium atoms to oriented nitromethane (CH3NO2) molecules

Electrons are transferred in collisions between potassium atoms and CH3NO2 molecules that have been oriented in space prior to collision. The electron transfer produces K+ ions, parent negative ions CH3NO2-, and the fragment ions e(-), NO2-, and O- in amounts that depend on the energy. The positive and negative ions are detected in coincidence by separate time-of-flight mass spectrometers at various collision energies for both CH3-end attack and NO2-end attack. The steric asymmetry for electrons and CH3NO2- is essentially zero, but the steric asymmetry for NO2- shows that NO2- is formed mainly in CH3-end collisions. There is evidence that the electrons and NO2- have the same transient precursor, despite having different steric asymmetries. It appears likely that the precursor is formed by electron transfer mainly in collisions normal to the molecular axis leading to near zero steric asymmetry for the electron. This transient precursor can also eject an NO,ion, which is more likely to be removed as KNO2 salt when K+ ions are near the NO2 end of the molecule, with the result that CH3-end collisions seem to produce more NO2-.