Which of the following is not a characteristic of the structure of benzene? O carbon atoms have trigonal planar geometry with bond angles of 120° O carbon atoms are sp2 hybridized O planar, six-membered ring C-C bonds of equal length at 1.39 Å O sp orbitals are responsible for the delocalized n bonding None
The Correct Answer and Explanation is:
Correct Answer: ❌ sp orbitals are responsible for the delocalized π bonding
Explanation
Benzene (C₆H₆) is an aromatic hydrocarbon with a highly symmetrical and stable structure that has fascinated chemists for over a century. Let’s analyze each option to identify the incorrect statement.
- Carbon atoms have trigonal planar geometry with bond angles of 120°
✅ True: Each carbon in benzene is bonded to two other carbon atoms and one hydrogen atom, forming three sigma (σ) bonds in a trigonal planar arrangement. This leads to bond angles of approximately 120°, consistent with sp² hybridization. - Carbon atoms are sp² hybridized
✅ True: In benzene, all carbon atoms use sp² hybrid orbitals to form sigma bonds with adjacent carbons and hydrogen atoms. The unhybridized p orbitals on each carbon overlap to form the delocalized π system. - Planar, six-membered ring C–C bonds of equal length at 1.39 Å
✅ True: X-ray diffraction studies have shown that all carbon–carbon bonds in benzene are of equal length, approximately 1.39 Å, intermediate between a typical single (1.54 Å) and double bond (1.34 Å). This uniformity is due to electron delocalization. - sp orbitals are responsible for the delocalized π bonding
❌ False: This is the incorrect statement. The delocalized π bonding in benzene arises from the sideways overlap of unhybridized p orbitals, not sp orbitals. The sp² orbitals form σ bonds, while the remaining unhybridized 2p orbital on each carbon atom overlaps with adjacent 2p orbitals to create the π system above and below the ring plane.
Conclusion:
The mistaken statement is that “sp orbitals are responsible for the delocalized π bonding.” In reality, the π bonding is due to unhybridized p orbitals, not the hybridized sp or sp² orbitals. Thus, this choice is not a characteristic of benzene’s structure.
