21. Aldehydes and Ketones: Nucleophilic Addition

Provide the chemical steps necessary for the following synthesis.

Which of the following correctly describes the synthesis of an acetal from an aldehyde ($\mathrm{acetal} a$) and a ketone ($\mathrm{acetal} b$)?

Which of the following sets of compounds are formed as the major organic products when an acetal is hydrolyzed in aqueous $H_{2}O$ and $\mathrm{HCl}$?

Which of the following compounds is classified as an acetal?

Provide the chemical steps necessary for the following synthesis.

Determine the starting materials based on the acetal group present.