In this experiment for an upper-division course in organic structure determination, each student prepares an unknown compound and characterizes the product using multiple spectroscopic techniques. The unknowns, 2-aryl-substituted 1,4-dihydro-3,1-benzoxazines and 1,2,3,4-tetrahydroquinazolines, are prepared in a single step by the condensation of commercially available aryl aldehydes with 2- aminobenzyl alcohol or 2-aminobenzylamine, respectively. The products are purified by recrystallization and characterized by their mass, IR, [superscript 1]H NMR, [superscript 13]C NMR, COSY, and HMQC spectra. Pre- and postlab assignments encourage students to use both mechanistic reasoning and information from multiple spectroscopic techniques for structure elucidation. (Contains notes and references.)