- Draw the Lewis structure for carbonyl fluoride, COF2. What are the electron-pair geometry and molecular geometry around the central atom? What is the hybridization of the carbon atom? What orbitals overlap to form the σ and π bonds between carbon and oxygen?
- Draw the Lewis structure for acetamide, CH3CONH2. What are the electron-pair geometry
and molecular geometry around the two C atoms? What is the hybridization of each of the C atoms? What orbitals overlap to form the σ and π bonds between carbon and oxygen?
The Correct Answer and Explanation is :
5. Carbonyl Fluoride (COF₂)
Lewis Structure
- Central atom: Carbon (C) is the central atom as it is less electronegative than oxygen (O) and fluorine (F).
- Valence electrons:
- Carbon: 4
- Oxygen: 6
- Fluorine (each): 7 × 2 = 14
- Total = 4 + 6 + 14 = 24 electrons.
- Carbon forms a double bond with oxygen and single bonds with two fluorine atoms. Oxygen has two lone pairs, and each fluorine has three lone pairs.
Geometry and Hybridization
- Electron-pair geometry: Trigonal planar (sp² hybridized carbon).
- Molecular geometry: Trigonal planar.
- Hybridization: sp² on carbon.
- Bond formation:
- σ bonds: sp² orbital on C overlaps with p orbital on O and sp³ orbitals on F.
- π bond: Overlap of unhybridized p orbitals on C and O.
6. Acetamide (CH₃CONH₂)
Lewis Structure
- Carbon in the CH₃ group is singly bonded to three H atoms and to the carbonyl C.
- Carbon in the carbonyl (C=O) is double-bonded to oxygen and single-bonded to NH₂.
- Oxygen has two lone pairs, and nitrogen has one lone pair.
Geometry and Hybridization
- CH₃ Carbon:
- Electron-pair geometry: Tetrahedral (sp³).
- Molecular geometry: Tetrahedral.
- Carbonyl Carbon:
- Electron-pair geometry: Trigonal planar (sp²).
- Molecular geometry: Trigonal planar.
Bond Formation
- σ bonds:
- sp³ orbitals of CH₃ C overlap with H 1s orbitals.
- sp² orbital of carbonyl C overlaps with O p orbital and sp³ orbitals of NH₂ N.
- π bond:
- Unhybridized p orbital on carbonyl C overlaps with p orbital on O.
Explanation (300 Words)
Lewis structures depict the bonding arrangement of molecules using valence electrons. In COF₂, the central carbon is bonded to an oxygen atom (via a double bond) and two fluorine atoms (via single bonds), with lone pairs on the surrounding atoms completing the octet. Carbon’s sp² hybridization aligns electron density in a trigonal planar geometry, optimizing bond angles to ~120°. The σ bonds form through overlap of sp² orbitals (carbon) with p orbitals (oxygen) and sp³ orbitals (fluorine). The π bond arises from parallel p orbital overlap between carbon and oxygen.
In acetamide, the molecule is a mix of sp² and sp³ hybridized carbons. The CH₃ carbon is sp³ hybridized, forming a tetrahedral geometry with bond angles near 109.5°. The carbonyl carbon is sp² hybridized with a planar arrangement around it. The NH₂ nitrogen’s lone pair contributes to hydrogen bonding and the molecule’s solubility in water. The σ bonds include sp²-sp² overlaps for the carbon-carbon bond, sp²-p overlap for the carbon-oxygen bond, and sp³ overlaps for the C-H and C-N bonds. The π bond in the carbonyl group is formed by unhybridized p orbitals on the carbon and oxygen atoms.
Understanding these structures and hybridizations is crucial in predicting molecular shapes, reactivity, and interactions in chemical systems.