To draw the Lewis dot structure for acetone (C3H6O), follow these steps:
- Determine the total number of valence electrons: Carbon (C) has 4 valence electrons, Hydrogen (H) has 1, and Oxygen (O) has 6. For acetone (C3H6O), the total number of valence electrons is (3 × 4) + (6 × 1) + 6 = 24.
- Draw the skeletal structure: The central carbon atom is bonded to two other carbon atoms and one oxygen atom. The two outer carbon atoms are each bonded to three hydrogen atoms.
- Distribute the remaining electrons to satisfy the octet rule: Place lone pairs on the oxygen atom and ensure each carbon atom has four bonds.
a) Identify any pi bonds present in this structure:
In the Lewis structure of acetone, the carbon-oxygen double bond (C=O) consists of one sigma bond and one pi bond. The pi bond is formed by the sideways overlap of p orbitals.
b) Identify the hybridization state and the bond angles/geometry for each carbon atom in the molecule:
- The central carbon atom (C1) is sp2 hybridized, with bond angles of approximately 120°, resulting in a trigonal planar geometry.
- The two outer carbon atoms (C2 and C3) are also sp2 hybridized, with bond angles of approximately 120°, resulting in a trigonal planar geometry.