Question

Two moles of benzaldehyde and one mole of acetone under alkaline conditions using aqueous NaOH after heating gives $x$ as the major product. The number of $\pi$ bonds in the product $x$ is ................

Answer 1

Correct Answer: 9

The reaction shown below is an example of an aldol condensation, where benzaldehyde and acetone react in the presence of a base (OH^-) and heat (Δ) to form a product.

$$ \text{Benzaldehyde (C}_6\text{H}_5\text{CHO}) + \text{Acetone (CH}_3\text{COCH}_3) \xrightarrow{\text{OH}^- , \Delta} $$
$$ \text{Product (C}_6\text{H}_5\text{CH=CHCOCH}_3) $$

The final product has a number of π-bonds involved in the conjugated system. The reaction involves the formation of a new carbon-carbon bond between the benzaldehyde and acetone.

$$ \text{Hence, the number of π-bonds in the product is 9.} $$

Answer 2

The reaction involved is an aldol condensation reaction. The mechanism is as follows:

The product is formed by the reaction of two molecules of benzaldehyde (PhCHO) and one molecule of acetone (CH$_3$COCH$_3$) in the presence of alkali and heat.
The reaction involves the removal of water (H$_2$O) through dehydration, leading to the formation of a conjugated system.
The major product contains:
-3 double bonds in the benzene ring (Ph),
-2 double bonds formed during the aldol reaction,
-carbonyl (C = O) group in the product.
Total $\pi$-bonds = 9.