Chapter 15, Problem 59P

Answer the following questions about curcumin, a yellow pigment isolated from turmeric, a tropical perennial in the ginger family and a principal ingredient in curry powder.

a. In Chapter 11 we learned that most enols, compounds that contain a hydroxy group bonded to a $\text{C=C}$, are unstable and tautomerize to carbonyl groups. Draw the keto form of the enol of curcumin, and explain why the enol is more stable than many other enols.

b. Explain why the enol $\text{O–H}$ proton is more acidic than an alcohol $\text{O–H}$ proton.

c. Why is curcumin colored?

d. Explain why curcumin is an antioxidant