Question

Cross aldol condensation occurs between

Options

• two same aldehydes

• two same ketones

• two different aldehydes and ketones

• None of these

Answer 1

two different aldehydes and ketones

Explanation:

In cross aldol condensation aromatic aldehydes or ketones (with or without α-hydrogen) react with aldehydes, ketones or esters having α-hydrogen atoms in the presence of dilute alkali to form a β-unsaturated carbonyl compound. Example,

(i) \[\ce{\underset{Benzaldehyde}{C6H5CHO} + \underset{Acetaldehyde}{CH3CHO} ->[OH-] C6H5CHOHCH2CHO ->[-H2O] \underset{Cinnamaldehyde}{C6H5CH = CHCHO}}\]

(ii)

\[\begin{array}{cc}
\phantom{........................}\ce{CH3}\phantom{.............}\ce{O}\phantom{..........................}\ce{CH3}\phantom{.......}\ce{O}\phantom{........................}\\
\phantom{.....................}|\phantom{................}||\phantom{...........................}|\phantom{..........}||\phantom{.....................}\\
\ce{\underset{Acetophenone}{C6H5 - C = O} + H3C - C - C6H5 ->[Aluminium][t-butoxide] C6H5 - \underset{Dypnone}{C = CH} - C - C6H5}
\end{array}\]