What is the lewis structure for COCl2?
The correct answer and explanation is:
Lewis Structure for Phosgene (COCl₂)
- Determine the total valence electrons:
- Carbon (C): 4 valence electrons.
- Oxygen (O): 6 valence electrons.
- Chlorine (Cl): 7 valence electrons (×2 for 2 atoms).
- Total = 4 + 6 + (7 × 2) = 24 valence electrons.
- Arrange the atoms:
- Carbon is the central atom because it is the least electronegative (besides hydrogen).
- Oxygen and the two chlorine atoms are placed around carbon.
- Create single bonds:
- Draw single bonds from carbon to oxygen and to each chlorine atom. This uses 6 electrons (2 per bond).
- Distribute remaining electrons:
- Subtract the used electrons: 24−6=1824 – 6 = 18 electrons left.
- Distribute these 18 electrons to complete the octets of oxygen and the two chlorine atoms:
- Oxygen gets 6 electrons (in addition to its bond with carbon).
- Each chlorine atom gets 6 electrons (in addition to their bonds).
- Check the octets:
- Carbon has only 6 electrons (from the 3 bonds). To complete its octet, form a double bond between carbon and oxygen.
- Finalize the structure:
- The final structure has:
- A double bond between carbon and oxygen.
- Single bonds between carbon and each chlorine atom.
- Oxygen has 4 lone electrons (2 lone pairs), and each chlorine atom has 6 lone electrons (3 lone pairs).
- The final structure has:
Lewis Structure:
O
||
Cl - C - Cl
Explanation :
The Lewis structure of COCl₂, phosgene, represents the bonding and non-bonding electron pairs in the molecule. Carbon is chosen as the central atom because it can form multiple bonds and is less electronegative than oxygen and chlorine. The molecule contains 24 valence electrons, calculated by summing the electrons from each atom (C: 4, O: 6, Cl: 7 × 2).
The single bonds to oxygen and the two chlorines initially consume 6 electrons. The remaining 18 electrons are distributed to complete the octets of the outer atoms. Oxygen and chlorine are highly electronegative, so they are prioritized in satisfying their octets. Initially, carbon has only 6 electrons around it (3 bonds). To achieve a stable octet for carbon, one lone pair from oxygen is converted into a bonding pair, forming a double bond between carbon and oxygen.
This arrangement ensures all atoms follow the octet rule, except for special cases like expanded octets, which are not relevant here. Oxygen ends up with two lone pairs, while each chlorine retains three lone pairs. This structure minimizes formal charges across the molecule, making it the most stable configuration.
The geometry of COCl₂ is trigonal planar, as carbon forms three regions of electron density (1 double bond and 2 single bonds). This arrangement arises due to sp² hybridization of carbon, which ensures that the molecule adopts a planar structure with bond angles close to 120°.