The labels on a shipment of the five chemicals a –e below were washed off by accident when the delivery truck went through a truckwash with the doors open. a clever student took infrared spectra of each of the resulting unknowns. unknown #1 had a strong, broad ir absorption at 3400–3600 cm–1, and no absorptions between 1600 and 2900 cm–1. unknown #2 had a strong absorption at 1680 cm–1 and no absorptions above 3100 cm–1. what are the structures of unknowns 1 and 2?