The labels on a shipment of the five chemicals a-e 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. structure a is a cyclic ketone. structure b is an alcohol bonded to a ring. structure c is an enone, which is a carbonyl bonded to an alkene. structure d contains both an amide and an alcohol. structure e is an ester. what is unknown #1