Core ionization potentials in dimethyl ether and methyl amine

The ionization potentials for core electrons in dimethyl ether and methyl amine have been measured. For carbon 1s electrons the values are 292.25(4) eV for the ether and 291.60(4) eV for the amine. The nitrogen 1s ionization potential is 405.15(4) eV; that for oxygen is 538.59(4) eV. The two ionization potentials for the ether are very close to those that have been reported for the related compound methanol. Those for methyl amine reflect the fact that nitrogen is more electro-negative than carbon. The carbon 1s ionization potential in methyl amine together with the equivalent cores approximation gives an estimate of 169 kcal/mole for the heat of formation of N₂H₅⁺. The corresponding proton affinity for hydrazine is 221 kcal/mole, very close to that of ammonia, 214 kcal/mole. The large shifts of nitrogen and oxygen core ionization potentials relative to N₂ and O₂ may be due to unusually low relaxation energies for the diatomic molecules rather than to high negative charges on the atoms in the respective compounds. Since different methods for estimating relaxation energies give results differing by as much as 6 eV, it is not possible to say which is the more important effect.