(a) Propose a structure for an amine A (C₄H₉N), which liberates a gas when treated with NaNO₂ and HCl. The ¹³C NMR spectrum of A is as follows, with attached protons in parentheses: δ 14(2), δ 34.3(2), δ 50.0(1).

(b) Propose a structure for an amine B (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 N—H absorption at 3300 cm^–1. The ¹³C NMR spectrum of B is as follows: δ 36.0, d 54.4, δ 115.8, δ 136.7.