Pyrrolidine is derived from pyrrol by complete hydrogenation. There are two insteresting structural features to note. First, the molecule assumes an envelope shape, that is the C-atoms are more or less in one plane and the N-atoms is significantly out of that plane. Secondly, the N-atom is pyramidal and the N-lone pair is oriented kind of perpendicular to the plane defined by the C-atoms. In your opinion, what is the advantage of this lone pair orientation as opposed to the alternative (H up and lone pair sort of equatorial)?