21. Aldehydes and Ketones: Nucleophilic Addition

What are the products of the following reactions?

f.

Propose a mechanism for the acid-catalyzed reaction of benzaldehyde with methanol to give benzaldehyde dimethyl acetal.

Propose a mechanism for the acid-catalyzed hydrolysis of cyclohexanone dimethyl acetal.

Propose a mechanism for the acid-catalyzed reaction of cyclohexanone with ethylene glycol to give cyclohexanone ethylene acetal.

Draw structures of the following derivatives.

(d) the ethylene acetal of hexan-3-one

Show what alcohols and carbonyl compounds give the following derivatives.

(a)

(b)

(c)

Propose a mechanism for the acid-catalyzed hydrolysis of cyclohexanone ethylene acetal.

Propose a mechanism for the acid-catalyzed hydrolysis of the acetal given in Problem 18-26(f).

For each compound,

1. name the functional group.

2. show what compound(s) result from complete hydrolysis.

(a)

The nucleosides that make up DNA have heterocyclic rings linked to deoxyribose by an aminoacetal functional group. Point out the aminoacetal linkages in deoxycytidine and deoxyadenosine.

Predict the products formed when cyclohexanecarbaldehyde reacts with the following reagents.

(e) propane-1,3-diol, H⁺

Predict the major products of the following reactions.

(e)

A chemist failed to generate the alcohol using the reaction shown here.

(b) How could the reaction conditions be modified to allow formation of the product?

Show how each of the following compounds could be prepared from the given starting material. Each requires a protecting group.

c.

Acetals can serve as protecting groups for 1,2-diols, as well as for aldehydes and ketones. When the acetal is formed from acetone plus the diol, the acetal is called an acetonide. Show the acetonides formed from these diols with acetone under acid catalysis.