Question

The radical is aromatic because it has

• A. 6 p-orbitals and 6 unpaired electrons
• B. 7 p-orbitals and 6 unpaired electrons
• C. 7 p-orbitals and 7 unpaired electrons
• D. 6 p-orbitals and 7 unpaired electrons

Answer 1

The Correct Option is A

The question asks which feature makes the given radical aromatic. Aromaticity is a concept in organic chemistry that describes the cyclic, planar arrangement of p-orbitals overlapping in a manner that leads to a delocalized π-electron system, following Huckel's rule (4n + 2 π-electrons, where n is an integer).

For a compound to be considered aromatic, it must satisfy the following conditions:

1. Be cyclic.
2. Be planar.
3. Have conjugated π-electrons (in p-orbitals).
4. Follow Huckel's rule, having (4n + 2) π-electrons.

Let's analyze the given radical:

The structure shown is a phenyl methyl radical (\text{C}_6\text{H}_5\text{CH}_2^\bullet). In its radical form, one electron from the sp³ carbon of the methyl group (•CH₂) is unpaired. The benzene ring itself contributes 6 π-electrons from the conjugated system.

• The benzene ring is made up of 6 carbon atoms and contributes 6 p-orbitals from these carbons.
• The unpaired electron from the radical makes the total number of π-electrons to be 6 (as only the benzene pi system is counted in aromaticity, the unpaired electron at the sp³ carbon offers no further π-electrons).

Thus, the molecule fits Huckel's rule for n=1: (4n + 2) = 6, where n is an integer.

The correct answer is therefore: 6 p-orbitals and 6 unpaired electrons.

The other options do not satisfy the conditions for aromaticity set by Huckel's rule.