Dichlorobenzene, C₆H₄Cl₂, exists in three forms (isomers) called ortho, meta, and para:
Which of these has a nonzero dipole moment?

Verified step by step guidance

1. Understand that dichlorobenzene (C_6H_4Cl_2) can exist in three isomeric forms: ortho, meta, and para, based on the relative positions of the chlorine atoms on the benzene ring.
2. Recall that a dipole moment arises from the difference in electronegativity between atoms, leading to a separation of charge.
3. Consider the molecular geometry of each isomer: in the ortho isomer, the chlorine atoms are adjacent; in the meta isomer, they are separated by one carbon atom; and in the para isomer, they are opposite each other on the benzene ring.
4. Analyze the symmetry of each isomer: the para isomer is symmetrical, which often leads to the cancellation of dipole moments, resulting in a net dipole moment of zero.
5. Conclude that the ortho and meta isomers have nonzero dipole moments due to their asymmetrical structures, which do not allow for complete cancellation of the dipole moments.

Key Concepts

Molecular Polarity

Molecular polarity refers to the distribution of electrical charge over the atoms in a molecule. A molecule is polar if it has a net dipole moment, which occurs when there is an uneven distribution of electron density, often due to differences in electronegativity between atoms. This results in one end of the molecule being partially positive and the other end being partially negative.

Dipole Moment

The dipole moment is a vector quantity that measures the separation of positive and negative charges in a molecule. It is calculated as the product of the charge and the distance between the charges. A nonzero dipole moment indicates that the molecule has a polar character, while a zero dipole moment suggests that the molecule is nonpolar, often due to symmetrical arrangements of atoms.

Isomerism in Organic Chemistry

Isomerism occurs when two or more compounds have the same molecular formula but different structural arrangements or spatial orientations. In the case of dichlorobenzene, the ortho, meta, and para isomers differ in the positions of the chlorine atoms on the benzene ring. These structural differences can significantly affect the physical properties of the compounds, including their polarity and dipole moments.