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Toluene reacts with succinic anhydride in the presence of anhydrous AlCl ₃ to form compound P as the major product. P is subjected to Clemmensen reduction ( Zn-Hg , conc. HCl ) to yield Q. Finally, Q is heated with concentrated H ₂ SO ₄ to form the bicyclic compound R. Identify the IUPAC names of the intermediate P and the final product R.

Options

  1. AP: 4-(4-methylphenyl)-4-oxobutanoic acid R: 7-methyl-3,4-dihydronaphthalen-1(2H)-one
  2. BP: 4-(2-methylphenyl)-4-oxobutanoic acid R: 5-methyl-3,4-dihydronaphthalen-1(2H)-one
  3. CP: 4-(4-methylphenyl)-4-oxobutanoic acid R: 6-methyl-3,4-dihydronaphthalen-1(2H)-one
  4. DP: 4-(4-methylphenyl)-4-oxobutanoic acid R: 1-butyl-4-methylbenzene

Correct answer

A. P: 4-(4-methylphenyl)-4-oxobutanoic acid R: 7-methyl-3,4-dihydronaphthalen-1(2H)-one

Step-by-step solution

Toluene undergoes Friedel-Crafts acylation with succinic anhydride. The methyl group is an activating and ortho/para directing group. Due to steric hindrance, the para product predominates, forming 4-(4-methylphenyl)-4-oxobutanoic acid (P). Clemmensen reduction ( Zn-Hg , conc. HCl ) selectively reduces the ketone carbonyl group to a methylene group without affecting the carboxylic acid, yielding 4-(4-methylphenyl)butanoic acid (Q). Heating Q with concentrated H ₂ SO ₄ causes an intramolecular Friedel-Crafts acylati

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