Compound A exist in equilibrium with its tautomeric form, compound B. An IR spectrum of a mixture of A and B exhibits four signals in the region 1600-1850 cm^-1. These signals appear at 1620, 1660, 1720 nd 1740 cm^-1. a. Identify the source for each of these four signals and provide a justification for the location of the signal at 1660 cm^-1
b. For most simple ketones, the concentration of the enol tautomer is almost negligible at equilibrium. However, in this case, the concentration of B is significant. Provide a justification for this observation.
c. The IR spectrum of compound C lacks a signal at 1720 cm^-1. Draw the tautomer of C and then determine which tautomeric form predominates at equilibrium. Explain your choice.