There are three isomers with molecular formula C₂H₂Cl₂. Draw their structures. Which one does not have a dipole moment?

Verified step by step guidance

1. Step 1: Understand the molecular formula C2H2Cl2. This indicates a molecule with two carbon atoms, two hydrogen atoms, and two chlorine atoms. The molecule can form isomers based on the arrangement of the chlorine atoms around the carbon-carbon double bond.
2. Step 2: Draw the three possible isomers of C2H2Cl2. These are: (1) cis-1,2-dichloroethene, where both chlorine atoms are on the same side of the double bond; (2) trans-1,2-dichloroethene, where the chlorine atoms are on opposite sides of the double bond; and (3) 1,1-dichloroethene, where both chlorine atoms are attached to the same carbon atom.
3. Step 3: Analyze the dipole moment of each isomer. Dipole moment arises due to the difference in electronegativity between atoms and the molecular geometry. In cis-1,2-dichloroethene, the dipoles from the chlorine atoms do not cancel out, resulting in a net dipole moment. In trans-1,2-dichloroethene, the dipoles from the chlorine atoms cancel out due to symmetry, resulting in no net dipole moment. In 1,1-dichloroethene, the dipoles do not cancel out, resulting in a net dipole moment.
4. Step 4: Identify the isomer without a dipole moment. Based on the analysis, trans-1,2-dichloroethene does not have a dipole moment because the molecule is symmetrical, and the dipoles cancel each other out.
5. Step 5: Confirm the reasoning by considering the molecular geometry and electronegativity differences. Chlorine is more electronegative than hydrogen, creating dipoles in the molecule. The spatial arrangement of these dipoles determines whether they cancel out or result in a net dipole moment.

Key Concepts

Isomerism

Isomerism refers to the phenomenon where two or more compounds have the same molecular formula but different structural arrangements or spatial orientations of atoms. In the case of C2H2Cl2, the isomers can differ in the connectivity of the carbon and chlorine atoms, leading to distinct chemical and physical properties.

Dipole Moment

A dipole moment is a measure of the separation of positive and negative charges in a molecule, which occurs due to differences in electronegativity between atoms. Molecules with polar bonds and an asymmetrical shape typically have a net dipole moment, while symmetrical molecules may have no dipole moment despite having polar bonds.

Electronegativity

Electronegativity is the tendency of an atom to attract electrons in a chemical bond. In the context of C2H2Cl2, chlorine is more electronegative than hydrogen, which influences the polarity of the bonds. Understanding electronegativity helps predict the dipole moments of the isomers based on their molecular geometry and the arrangement of electronegative atoms.