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JEE MAIN 2026 · Hydrocarbons

JEE Main 2026 Session 2 Question Paper: 8 Apr, Shift 2 (B.E./B.Tech), question 64

Updated
Single correct+4 / -1Answer matches NTA’s final key

The total number of aromatic compounds/species from the following is

Six structures: p-benzoquinone; the cycloheptatrienyl (tropylium) cation; phenanthrene; 1,2-dihydronaphthalene; a cyclobutene ring carrying two positive charges (cyclobutadienyl dication); a six-membered ring with two C=C bonds, a negative charge on one carbon and one CH2 carbon

Choose one

Solution

Solution

Apply Hückel's rule to each ring system as a whole: cyclic, planar, fully conjugated, with (4n+2)(4n + 2) π electrons.

Species Verdict
p-Benzoquinone Not aromatic: the π electrons are in C=O and isolated C=C bonds, not a continuous ring current
Tropylium cation Aromatic: 7 sp² carbons, 6 π electrons
Phenanthrene Aromatic: fully conjugated, 14 π electrons
1,2-Dihydronaphthalene Not counted: the CH2_2–CH2_2 unit breaks conjugation of the second ring, so the bicyclic system as a whole is not aromatic
Cyclobutadienyl dication Aromatic: 4 sp² carbons, 2 π electrons (n=0n = 0)
Cyclohexadienyl anion (as drawn) Not aromatic: the ring still contains an sp³ CH2_2, so conjugation is not continuous

That makes 3 aromatic species, which is the official answer. (Strictly, 1,2-dihydronaphthalene still contains one benzene ring; the question treats each structure as a whole system.)

Answer: 3.

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

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