For COCl2 and predict the hybridization state, molecular geometry. Draw Lewis structure and approximate bond angle around the central atom.
The Correct Answer and Explanation is:
Compound: COCl₂ (Phosgene)
1. Lewis Structure:
- Carbon (C) is the central atom.
- It forms:
- One double bond with oxygen (O).
- Two single bonds with two chlorine (Cl) atoms.
- There are no lone pairs on carbon.
- Oxygen and chlorine atoms each have lone pairs to complete their octets.
Lewis Structure:
mathematicaCopyEdit O
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Cl–C–Cl
Each Cl has 3 lone pairs; O has 2 lone pairs.
2. Hybridization:
- Carbon forms 3 sigma bonds (1 with O and 2 with Cl).
- It needs three hybrid orbitals → sp² hybridization.
3. Molecular Geometry:
- With 3 electron domains and no lone pairs on the central atom, the molecular geometry is trigonal planar.
- Electron geometry is also trigonal planar.
4. Bond Angle:
- Ideal bond angle in a trigonal planar structure is approximately 120°.
Explanation:
Phosgene (COCl₂) is a toxic chemical compound once used as a chemical warfare agent. Understanding its structure begins with constructing the Lewis structure, which involves identifying how many valence electrons are available and how atoms are bonded. Carbon contributes 4 valence electrons, oxygen has 6, and each chlorine has 7. The total is 24 valence electrons.
Carbon is the central atom and forms a double bond with oxygen and single bonds with each chlorine, fulfilling the octet rule for each atom. The double bond to oxygen involves a sigma and a pi bond, while each bond to chlorine is a single sigma bond.
The central atom, carbon, has three regions of electron density (two single bonds and one double bond), so it adopts sp² hybridization to form three sp² hybrid orbitals for the sigma bonds. The remaining unhybridized p orbital overlaps with a p orbital from oxygen to form the pi bond of the double bond.
With sp² hybridization, the molecular geometry is trigonal planar, meaning that the three atoms (O, Cl, Cl) bonded to carbon lie in a plane, and the bond angles are ideally 120°. This geometry minimizes electron pair repulsion around the central carbon atom according to VSEPR (Valence Shell Electron Pair Repulsion) theory.
The molecule is also polar due to the electronegativity difference between oxygen and chlorine, and the asymmetrical shape results in a net dipole moment.
In summary, COCl₂ has an sp² hybridized central carbon, a trigonal planar shape, and ~120° bond angles, all consistent with basic chemical bonding and molecular geometry principles.
