21. Aldehydes and Ketones: Nucleophilic Addition

Which of the following structures is classified as a hemiacetal?

Which of the following compounds is a hemiacetal?

Which of the following compounds is the hemiacetal formed when $\mathrm{ethanol}$ reacts with $\mathrm{propanal}$?

Draw structures of the following derivatives.

(h) the hemiacetal form of 5-hydroxypentanal

Identify the hemiacetal functional group in each of the following molecules. These molecules may not be stable enough to be the favorable product in an equilibrium reaction.

(c)

Provide a mechanism for the formation of the hemiacetals shown. [Only (c) is favored as written.]

(a)

Which of the following cyclic hemiacetals would you expect to have the highest K_eq for their formation? Explain your answer.

(a)