Propose a structure for an amine of formula C4H9N, which does not liberate a gas when treated with NaNO2 and HCl, and has IR absorptions at 917 cm-1, 990 cm-1, and 1640 cm-1, as well as an N-H absorption at 3300 cm-1. The 13C NMR spectrum is as follows: ? 36.0, ? 54.4, ? 115.8, ? 136.7.