Explain why one of the three structures of C2H2Cl2 is nonpolar and the other two are molecular dipoles.
The Correct Answer and Explanation is :
C₂H₂Cl₂ (dichloroethene) exists in three isomeric structures: cis-1,2-dichloroethene, trans-1,2-dichloroethene, and 1,1-dichloroethene. The polarity of each isomer depends on its molecular geometry and the distribution of electron density, which affects dipole moment creation.
Explanation:
- Cis-1,2-Dichloroethene (Molecular Dipole):
In the cis isomer, the chlorine atoms are positioned on the same side of the double bond. This creates an uneven distribution of electron density, as the electronegative chlorine atoms pull electron density toward themselves. The geometry of the molecule results in a net dipole moment because the vectors of the dipoles from each C-Cl bond do not cancel out. Therefore, cis-1,2-dichloroethene has a molecular dipole. - Trans-1,2-Dichloroethene (Nonpolar):
In the trans isomer, the chlorine atoms are positioned on opposite sides of the double bond. This symmetrical arrangement allows the dipoles from the two C-Cl bonds to cancel out, as the dipoles point in opposite directions with equal magnitude. This results in no net dipole moment, meaning trans-1,2-dichloroethene is nonpolar. - 1,1-Dichloroethene (Molecular Dipole):
In the 1,1-isomer, both chlorine atoms are attached to the same carbon. This creates a polar molecule because both C-Cl bonds point in the same direction, and their dipoles do not cancel out. Therefore, 1,1-dichloroethene is polar, as the dipole moment does not cancel.
Summary:
- Cis-1,2-dichloroethene: Polar (net dipole moment).
- Trans-1,2-dichloroethene: Nonpolar (no net dipole moment due to symmetry).
- 1,1-dichloroethene: Polar (net dipole moment due to unequal distribution of electron density).
I’ll generate an image to illustrate the molecular structures of these isomers.
Here is the image showing the three isomers of C₂H₂Cl₂ (dichloroethene), highlighting the molecular structures and the positioning of chlorine atoms. The dipoles for the polar molecules are indicated by arrows. Let me know if you need further clarification!
