Correct Answer - Option 3 : 4n + 2
In organic chemistry, Hückel's rule predicts whether a planar ring molecule will have aromatic properties.
- The pi-electron count is defined by the series of numbers generated from 4n+2 where n = zero or any positive integer (i.e, n = 0, 1, 2, etc.).
- The most common case in six pi electrons (n = 1) is found for example in benzene, pyrrole, furan, and pyridine.
- For a compound to be considered aromatic, it must be flat, cyclic, and conjugated and it must obey Huckel's rule.
- Huckel's Rule (4n+2 rule): To be aromatic, a molecule must have a certain number of pi electrons (electrons with pi bonds, or lone pairs within p orbitals) within a closed loop of parallel, adjacent p orbitals.
- π bonds are simply the second bond made in a double bond. Any pure double bond is one sigma/σ and one pi/π bond.
Hence we can conclude that the formulae of prediction aromatic property of plane ring is 4n + 2
