Organic of the following which has a zero dipole moment… CO2, Cl2C=CCl2, HOCH2CH2OH, HCl2CCHCl2 OR ALL HAVE ZERO DIPOLE MOMENTS? AND WHY?
The Correct Answer and Explanation is :
The correct answer is CO₂.
Explanation:
A molecule’s dipole moment depends on its shape and the arrangement of polar bonds. Let’s evaluate each molecule:
- CO₂ (Carbon dioxide)
- Geometry: Linear (O=C=O).
- Bond polarity: C=O bonds are polar because oxygen is more electronegative than carbon.
- Symmetry: The two polar C=O bonds are arranged in opposite directions and cancel each other out due to the linear geometry.
- Dipole moment: Zero (net dipole cancels out).
- Cl₂C=CCl₂ (Tetrachloroethene)
- Geometry: Planar (sp² hybridized carbons, with chlorines symmetrically placed around the double bond).
- Bond polarity: C-Cl bonds are polar because chlorine is more electronegative than carbon.
- Symmetry: The molecule is symmetric, so the dipoles cancel each other out.
- Dipole moment: Zero (symmetry cancels net dipole).
- HOCH₂CH₂OH (Ethylene glycol)
- Geometry: Nonlinear and flexible due to the hydroxyl groups.
- Bond polarity: O-H bonds are highly polar, and the two hydroxyl groups are not symmetrically arranged.
- Symmetry: Asymmetry causes the dipoles to not cancel.
- Dipole moment: Non-zero.
- HCl₂C-CHCl₂ (1,1,2,2-Tetrachloroethane)
- Geometry: Nonlinear (sp³ carbons, tetrahedral arrangement around each carbon).
- Bond polarity: C-Cl bonds are polar.
- Symmetry: The molecule lacks sufficient symmetry for dipole cancellation.
- Dipole moment: Non-zero.
Conclusion:
Both CO₂ and Cl₂C=CCl₂ have zero dipole moments due to their symmetry, which cancels out the polar bonds’ effects. However, only CO₂ is guaranteed to have a zero dipole moment regardless of its phase or rotation, making it the most unambiguous answer.