Aspirin is the brand name for acetylsalicylic acid, which is the common name for 2-(acetyloxy)benzoic acid. This compound looks like this:
In a single bond, you have a single ##sigma## bond.
In a double bond, there is one ##pi## bond in addition to the single ##sigma## bond that constituted the single bond.
Thus, if we treat each double bond as a single bond on this structure, we count up the ##sigma## bonds as:
- 5 ##”C”-“O”## ##sigma## bonds (2 from the carboxylic acid group, and 3 from the acetate group)
- 2 non-aromatic ##”C”-“C”## ##sigma## bonds (1 from the carboxylic acid group, and 1 on the acetate group)
- 6 aromatic ##”C”-“C”## ##sigma## bonds (on the benzene ring)
Then, in accounting for the particular bonds that are double bonds, the remaining ##pi## bonds are from:
- 2 ##”C”-“O”## ##pi## bonds (1 from the carboxylic acid group, and 1 from the acetate group)
- 3 aromatic ##”C”-“C”## ##pi## bonds (on the benzene ring)
Thus, we have 5 + 2 + 6 = 13 ##mathbf(sigma)## bonds and 2 + 3 = 5 ##mathbf(pi)## bonds.
