When d-glucose is treated with an aqueous bromine solution (buffered to a pH of 6), an aldonic acid is formed called d-gluconic acid. Treatment of d-gluconic acid with an acid catalyst produces a lactone (cyclic ester) with a six-membered ring.

(a) Draw the structure of d-gluconic acid.

(b) Draw the structure of the lactone formed from d-gluconic acid, showing the configuration at each chirality center.

(c) Would you expect this lactone to be optically active?

(d) Explain how you would distinguish between the d-gluconic acid and the lactone using IR spectroscopy.