Ortho-Dichlorobenzene, C₆H₄Cl₂, is obtained when two of the adjacent hydrogen atoms in benzene are replaced with Cl atoms. A skeleton of the molecule is shown here. (b) Are there any resonance structures for the molecule? If so, sketch them.

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1. <em>Ortho</em>-Dichlorobenzene is a derivative of benzene where two adjacent hydrogen atoms are replaced by chlorine atoms, resulting in the molecular formula C_6H_4Cl_2.
2. In benzene, resonance structures arise due to the delocalization of electrons within the conjugated pi system of the carbon ring.
3. For <em>ortho</em>-dichlorobenzene, the presence of chlorine atoms affects the electron distribution, but the basic benzene ring structure still allows for resonance.
4. To determine if resonance structures exist, consider the movement of pi electrons around the benzene ring, keeping in mind that the chlorine atoms can participate in resonance due to their lone pairs.
5. Sketch the resonance structures by showing the possible locations of double bonds and the delocalization of electrons, ensuring that the overall structure maintains the aromatic stability of the benzene ring.

Key Concepts

Resonance Structures

Resonance structures are different ways of drawing a molecule that represent the same arrangement of atoms but differ in the distribution of electrons. In molecules like ortho-dichlorobenzene, resonance helps to illustrate how electrons are delocalized across the structure, affecting stability and reactivity. These structures are not real, but rather a way to visualize the electron distribution in a molecule.

Delocalization of Electrons

Delocalization of electrons refers to the phenomenon where electrons are not confined to a single bond or atom but are spread out over several atoms. In ortho-dichlorobenzene, the presence of resonance allows for the electrons in the π system to be shared among multiple carbon atoms, which contributes to the molecule's stability and influences its chemical properties.

Molecular Geometry and Hybridization

Molecular geometry and hybridization describe the spatial arrangement of atoms in a molecule and the mixing of atomic orbitals to form new hybrid orbitals. In ortho-dichlorobenzene, the carbon atoms are sp² hybridized, leading to a planar structure that allows for effective overlap of p orbitals, facilitating resonance. Understanding these concepts is crucial for visualizing the molecule's shape and predicting its behavior in chemical reactions.