PrepRung
Sign inSign up free

JEE Main 2016 · Chemistry · General Organic Chemistry and Isomerism · medium

The number of aromatic species among the following is: cyclopentadienyl anion, cycloheptatrienyl cation, cyclooctatetraene, pyridine, cyclopropenyl…

Single correct option

The number of aromatic species among the following is: cyclopentadienyl anion, cycloheptatrienyl cation, cyclooctatetraene, pyridine, cyclopropenyl cation and cyclopentadienyl cation.
  1. A. 3
  2. B. 5
  3. C. 6
  4. D. 4
Show answer and solution

Answer: (D) 4

Aromaticity requires a planar, cyclic, fully conjugated system with (4n+2) π(4n+2)\,\pi electrons. Cyclopentadienyl anion (6π6\pi), cycloheptatrienyl (tropylium) cation (6π6\pi), pyridine (6π6\pi) and cyclopropenyl cation (2π2\pi) all satisfy this. Cyclooctatetraene (8π8\pi) is non-planar (tub-shaped) and non-aromatic, and the cyclopentadienyl cation has 4π4\pi electrons, so it is antiaromatic. Total =4=4.
Report a mistake

Original question written in the JEE Main 2016 pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake