What are factors (such as sterichinderence, electronic and resonance) affects the amine inversion?

Hello

Amine basicity correlates with, among other things, the hybridization of the nitrogen orbital that is holding the lone pair of electrons. The less s-character in this orbital, the more basic the amine. So, a trialkylamine (the lone pair is in ansp3 orbital) is more basic (less acidic or higherpKap) than the lone pair in pyridine (the lone pair is in ansp2 orbital), which is less acidic then the lone pair in a nitrile (the lone pair is in ansp orbital).\

The rate of nitrogen inversion also correlates with, among other things, hybridzation. But in cases where these "other things", such as ring constraints, limit nitrogen inversion, then the rate of nitrogen inversion may not correlate with hybridization. So the rate of nitrogen inversion does not always correlate with hybridization and is therefore not a good indicator of lone pair "availability".