' … ' is the product which is obtained…

Numerical answer+4 / -1Answer matches NTA’s final key

' $x$ ' is the product which is obtained from benzene by reacting it with carbon monoxide and hydrogen chloride in the presence of cuprous chloride. ' $y$ ' is the major product obtained from the benzene by reacting it with ethanoyl chloride in the presence of anhydrous AlCl $_3$ . Product (major) obtained by heating $x$ and $y$ in the presence of alkali is $z$ . Total number of $\pi$ (pi) electrons in $z$ is ______.

Your answer

Solution

$x$ : CO + HCl with CuCl/AlCl $_3$ formylates benzene (Gattermann–Koch): benzaldehyde, C $_6$ H $_5$ CHO.
$y$ : Friedel–Crafts acylation with ethanoyl chloride: acetophenone, C $_6$ H $_5$ COCH $_3$ .
$z$ : In alkali, the enolate of acetophenone attacks benzaldehyde (which has no α-hydrogen) and the aldol dehydrates (Claisen–Schmidt condensation): chalcone, C $_6$ H $_5$ CH=CH–CO–C $_6$ H $_5$ .

π electrons in chalcone: two benzene rings ( $6 + 6$ ), one C=C ( $2$ ) and one C=O ( $2$ ): $16$ .

Answer: 16.

Answer checked against the official answer key. The solution is our own working.

JEE MAIN 2026 · Organic Compounds Containing Oxygen

Solution

Keep going