25. Condensation Chemistry

What product can be isolated from the following aldol condensation reaction?

Provide the mechanism for the following transformation.

A student tried to prepare the following compounds using aldol condensations. Which of these compounds was she successful in synthesizing? Explain why the other syntheses were not successful.

Describe how the following compounds can be prepared using an aldol addition in the first step of the synthesis:

c.

Describe how the following compounds can be prepared using an aldol addition in the first step of the synthesis:

b.

Describe how the following compounds can be prepared using an aldol addition in the first step of the synthesis:

a.

Identify A–C. (Hint: A shows three singlets in its 1H NMR spectrum with integral ratios 3 : 2 : 3 and gives a positive iodoform test; see Problem 58.)

What aldol addition product is formed from each of the following compounds?

b.

What aldol addition product is formed from each of the following compounds?

a.

An aldol addition can be catalyzed by acids as well as by bases. Propose a mechanism for the acid-catalyzed aldol addition of propanal.

Draw the products of the following reactions:

b.

The following compounds can be synthesized by aldol condensations, followed by further reactions. (In each case, work backward from the target molecule to an aldol product, and show what compounds are needed for the condensation.)

(c)

The following compounds can be synthesized by aldol condensations, followed by further reactions. (In each case, work backward from the target molecule to an aldol product, and show what compounds are needed for the condensation.)

(b)