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JEE Main 2026 · 4 Apr · Shift 1, Chemistry question 72

Consider the following sequence of reactions to give the major product (X)

P g of the major product (X) formed is reacted with NaHCOX3\ce{NaHCO3} solution to liberate a gas which occupied 11.2 dm³ at STP.
P = ________ g.
(Given molar mass in g mol−1^{-1} H:1, C:12, O:16, Cl:35.5)

Benzene → (i) CH₃Cl/anhydrous AlCl₃; (ii) Cl₂/FeCl₃; (iii) K₂Cr₂O₇/H₂SO₄ → (X) major product.
Answer and worked solution

Official answer: 78

Sequence.

  • Friedel-Crafts methylation gives toluene.
  • ClX2\ce{Cl2}/FeClX3\ce{FeCl3} gives p-chlorotoluene (major).
  • Dichromate oxidises the methyl: X = p-chlorobenzoic acid (156.5 g mol⁻¹).

With NaHCOX3\ce{NaHCO3} each mole of acid gives one mole of COX2\ce{CO2}: 11.2 dm³ at STP = 0.5 mol.

Mass. 0.5×156.5=78.25≈780.5\times156.5=78.25\approx78 g.

Answer: 78

Topics:Carboxylic acidsAromatic hydrocarbons and electrophilic substitution
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