Chapter 3 - Exercises - Page 150e: 91

See the explanation

The observation that there are only three different structures of dichlorobenzene (C6H4Cl2) supports the concept of resonance in the localized electron model. In the localized electron model, the structure of a molecule is represented by a single Lewis structure, which does not account for the delocalization of electrons. However, the concept of resonance suggests that the actual structure of a molecule is a superposition of multiple contributing structures, known as resonance structures. The fact that there are only three different structures of dichlorobenzene can be explained by the concept of resonance as follows: 1. Ortho-dichlorobenzene (1,2-dichlorobenzene): - In this structure, the two chlorine atoms are positioned adjacent to each other on the benzene ring. - The resonance structures for this isomer involve the delocalization of electrons around the benzene ring, with the chlorine atoms occupying the adjacent positions. 2. Meta-dichlorobenzene (1,3-dichlorobenzene): - In this structure, the two chlorine atoms are positioned with one carbon atom between them on the benzene ring. - The resonance structures for this isomer involve the delocalization of electrons around the benzene ring, with the chlorine atoms occupying the meta positions. 3. Para-dichlorobenzene (1,4-dichlorobenzene): - In this structure, the two chlorine atoms are positioned opposite each other on the benzene ring. - The resonance structures for this isomer involve the delocalization of electrons around the benzene ring, with the chlorine atoms occupying the para positions. The fact that there are only three different structures of dichlorobenzene supports the concept of resonance because it suggests that the actual structure of the molecule is a superposition of multiple contributing structures, rather than a single fixed structure. This delocalization of electrons, as described by the resonance concept, explains the observed limited number of dichlorobenzene isomers.