Tertiary amine

Tertiary amine.

In the topic of Chemical Bonding, we discussed VSEPR (Valence Shell Electron Pair Repulsion Theory), which, based on the number of regions of high electron density around a central atom can be used to predict structures of certain molecules or ions. VSEPR questions on the MCAT are relatively common, especially those involving geometries in which nonbonded pairs of electrons are occupying positions in the geometry. There is a tendency for less-informed students to forget the nonbonded pairs and assign an incorrect geometry. You should be prepared for VSEPR questions involving amines. Amines possess a structure based on the tetrahedron with one position occupied by a nonbonding pair, so the geometry of substituents around nitrogen in an amine is pyramidal.