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, 1H NMR, 13C 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.
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