Chapter 15, Problem 60P

Stanozolol is an anabolic steroid that promotes muscle growth. Although stanozolol has been used by athletes and body builders, many physical and psychological problems result from prolonged use and it is banned in competitive sports.

a. Explain why the nitrogen heterocycle—a pyrazole ring—is aromatic.

b. In what type of orbital is the lone pair on each $\text{N}$ atom contained?

c. Draw all reasonable resonance structures for stanozolol.

d. Explain why the $\text{p}{K}_{\text{a}}$ of the $\text{N}-\text{H}$ bond in the pyrazole ring is comparable to the $\text{p}{K}_{\text{a}}$ of the $\text{O}-\text{H}$ bond, making it considerably more acidic than amines such as ${\text{CH}}_{\text{3}}{\text{NH}}_{\text{2}}$ ( $\text{p}{K}_{\text{a}}=40$).