Question

The carbon bond length in benzene is:

• A. in between C\(_2\)H\(_6\) and C\(_2\)H\(_4\)
• B. same as in C\(_2\)H\(_4\)
• C. in between C\(_2\)H\(_6\) and C\(_2\)H\(_2\)
• D. in between C\(_2\)H\(_4\) and C\(_2\)H\(_2\)

Hint:

Due to resonance, all C–C bonds in benzene are identical and have bond order 1.5, giving a bond length intermediate between single and double bonds.

Answer 1

The Correct Option is A

Step 1: Recall carbon–carbon bond lengths in different hydrocarbons.

C–C single bond (as in C\(_2\)H\(_6\)) \(\approx 1.54\ \text{\AA}\)
C=C double bond (as in C\(_2\)H\(_4\)) \(\approx 1.34\ \text{\AA}\)
C\(\equiv\)C triple bond (as in C\(_2\)H\(_2\)) \(\approx 1.20\ \text{\AA}\)
Step 2: Nature of bonding in benzene. In benzene, all six carbon–carbon bonds are equivalent due to resonance. Each C–C bond has partial double bond character (bond order \(= 1.5\)). Step 3: Bond length in benzene. The C–C bond length in benzene is approximately: \[ 1.39\ \text{\AA} \] This value lies between the bond lengths of:

C–C single bond (C\(_2\)H\(_6\))
C=C double bond (C\(_2\)H\(_4\))
Step 4: Final conclusion. Hence, the carbon bond length in benzene lies in between C\(_2\)H\(_6\) and C\(_2\)H\(_4\).