What is the bond order of the C-C
bonds in the benzene molecule? (enter a decimal number) In which species
or
are the
bond(s) longer? In which species
or
are the
bond(s) stronger?
The Correct Answer and Explanation is:
Correct Answers:
- Bond order of C–C bonds in benzene:
1.5 - In which species (C₆H₆ or C₂H₆) are the C–C bonds longer?
C₂H₆ - In which species (C₆H₆ or C₂H₆) are the C–C bonds stronger?
C₆H₆
Explanation (around 300 words):
Benzene (C₆H₆) is a unique organic molecule with a six-membered carbon ring and alternating double bonds. However, its structure is best described using the concept of resonance. In benzene, the electrons in the pi bonds are delocalized over the entire ring, creating a stable and symmetrical molecule. This delocalization causes all six carbon–carbon bonds to be equivalent in length and strength.
The bond order is a measure of the number of chemical bonds between a pair of atoms. In a regular single bond, the bond order is 1, and in a double bond, it is 2. Because benzene’s bonding is evenly distributed between single and double character, the bond order of each carbon–carbon bond in benzene is 1.5. This reflects the average between a single and a double bond due to the resonance structure.
C₂H₆ (ethane) is a simple alkane where the carbon–carbon bond is a single sigma bond, giving it a bond order of 1. Since bond length is inversely related to bond strength and order, the single bond in C₂H₆ is longer than the delocalized partial double bond in benzene. Therefore, C–C bonds are longer in C₂H₆.
Stronger bonds are usually shorter and have higher bond orders. Because benzene has a bond order of 1.5 compared to 1 in C₂H₆, its carbon–carbon bonds are stronger. This additional strength comes from the resonance stabilization of the molecule. As a result, C–C bonds are stronger in C₆H₆ than in ethane.
Understanding these differences highlights how resonance affects the chemical properties of aromatic compounds like benzene compared to saturated molecules like alkanes.
