Draw the Lewis structure for CH3NCO, a neutral molecule.
The correct answer and explanation is :
Lewis Structure of CH₃NCO (Methyl Isocyanate)
The molecular formula CH₃NCO corresponds to methyl isocyanate, a compound containing carbon (C), hydrogen (H), nitrogen (N), and oxygen (O). To draw its Lewis structure, follow these steps:
- Count the total valence electrons:
- Carbon (C): 4 valence electrons (2 atoms → 4 × 2 = 8)
- Hydrogen (H): 1 valence electron (3 atoms → 1 × 3 = 3)
- Nitrogen (N): 5 valence electrons (1 atom → 5)
- Oxygen (O): 6 valence electrons (1 atom → 6)
- Total valence electrons = 4 + 3 + 5 + 6 = 18 electrons.
- Identify the molecular connectivity:
- The CH₃ (methyl group) is typically bonded to nitrogen (N).
- The N=C=O (isocyanate group) structure is a well-known functional group.
- Thus, the connectivity is CH₃—N=C=O.
- Arrange the atoms and distribute electrons:
- Carbon (C) forms a double bond with oxygen (O).
- Nitrogen (N) forms a single bond with the methyl (CH₃) group and a double bond with carbon (C).
- Hydrogen (H) atoms are attached to the carbon (C) in CH₃.
- Assign lone pairs:
- Oxygen (O) has two lone pairs.
- Nitrogen (N) has one lone pair.
Final Lewis Structure:
H
|
H—C—N=C=O
|
H- CH₃ is single-bonded to nitrogen (N).
- N has a double bond with C.
- C has a double bond with O.
- Oxygen has two lone pairs.
- Nitrogen has one lone pair.
Explanation of Stability:
- The structure follows the octet rule for all atoms.
- Carbon (C) and oxygen (O) achieve full octets through double bonds.
- Nitrogen (N) maintains an octet with one lone pair.
- The molecule is neutral, meaning all atoms have formal charges close to zero.
This structure correctly represents CH₃NCO (methyl isocyanate) and explains its bonding.