The total bond order between adjacent carbon atoms of benzene is

Concept:

Bond order:

• Bond order is the number of bonding pairs of electrons between two atoms.
• In a covalent bond; a single bond has a bond order of one, a double bond has a bond order of two, and a triple bond has a bond order of 3
• Nonbonding electrons and antibonding electrons are not considered for the determination of the bond order.

Bond order

= \({{\left( {{\rm{Number\; of\; electrons\; in\; BMO - Number\;of\; electrons\; in\; ABMO}}} \right)} \over {\rm{2}}}\).

Explanation:

• The molecular formula of benzene is C₆H₆. Benzene has 6 C-C single bond. For each C-C single bond, it has 2 bonding electrons. B.O for each C-C single bond

 \( = {{\left( {2 - 0} \right)} \over {\rm{2}}}\)

\( = 1\)

• Benzene has a 6 pi molecular orbital. 
• The number of electrons in the pi-bonding molecular orbital of benzene is 6. While there are no electrons in the antibonding molecular orbital.
• Thus, for benzene the pi bond order

​\( = {{\left( {6 - 0} \right)} \over {\rm{2}}}\)

\( = 3\)

• This is the pi bond order for 6 C-C bonds.
• The bond order for each C-C bond in benzene is

​\( = 1 + 0.5\)

\( = 1.5\)

Conclusion:

Hence, the total bond order between adjacent carbon atoms of benzene is 1.5