Chemistry 336 Sample NMR Question #1 Winter 2001

Consider the following reaction sequence. Benzyl bromide and a slight excess of ethyl amine are heated for 1 hour. Upon workup, two products A and B are obtained in 90% and 10% yield, respectively. Use the given spectral parameters to deduce the chemical structures of A and B and assign the NMR resonances.

NMR Spectrum of A	NMR Spectrum of B
a 5H, 7.21 ppm, m	5H, 7.21 ppm, m
b 2H, 3.74 ppm, s	2H, 3.74 ppm, s
c 2H, 2.84 ppm, q	4H, 2.84 ppm, q
d 3H, 1.21 ppm, t	6H, 1.21 ppm, t
e 1H broad resonance at ~2.6 ppm
IR Spectrum: ~3350 cm&endash;1 (broad) No resonance at ~1700 cm-1	IR Spectrum: No strong resonances at >3200 cm-1 or at ~1700 cm-1

The product A from the first reaction was heated with excess methyl iodide for 1 hour and then the methyl iodide was evaporated off. The residue was mixed with allylic alcohol in the presence of triethylamine (a weak base). After 30 minutes the mixture was treated with diborane for 30 minutes and it was then treated with hydrogen peroxide in an aqueous sodium hydroxide solution. After work-up the crude material was chromatographed and one major product (C₁₀H₁₄O₂) was isolated. Use the given spectral parameters to deduce the chemical structure of the final product and assign the NMR resonances.