For each of the following compounds,
1. draw the Lewis structure.
2. show how the bond dipole moments (and those of any nonbonding pairs of electrons) contribute to the molecular dipole moment.
3. estimate whether the compound will have a large, small, or zero dipole moment.
d.

Verified step by step guidance

1. Draw the Lewis structure for acetone (CH3COCH3). Start by arranging the carbon atoms in a chain with the central carbon double-bonded to an oxygen atom. Each carbon atom should have four bonds, and the oxygen should have two lone pairs.
2. Identify the bond dipole moments. The C=O bond is polar due to the difference in electronegativity between carbon and oxygen, with the dipole pointing towards the oxygen. The C-H bonds are less polar, with dipoles pointing towards the carbon.
3. Consider the molecular geometry. Acetone is a trigonal planar molecule around the central carbon, which affects how the dipoles add up.
4. Analyze the contribution of each dipole to the overall molecular dipole moment. The C=O bond has a significant dipole moment, while the dipoles from the C-H bonds on the methyl groups partially cancel each other out.
5. Estimate the overall dipole moment. Due to the strong dipole of the C=O bond and the geometry of the molecule, acetone is expected to have a moderate to large dipole moment.

Key Concepts

Lewis Structure

The Lewis structure is a diagrammatic representation of a molecule showing how the valence electrons are distributed among the atoms. It helps in visualizing the bonding between atoms and any lone pairs of electrons. For acetone (CH3COCH3), the central carbon atom is double-bonded to oxygen and single-bonded to two methyl groups, with oxygen having two lone pairs.

Bond Dipole Moment

Bond dipole moments arise from differences in electronegativity between bonded atoms, creating a partial charge separation. In acetone, the C=O bond has a significant dipole moment due to oxygen's higher electronegativity compared to carbon, resulting in a partial negative charge on oxygen and a partial positive charge on carbon. This contributes to the overall molecular dipole moment.

Molecular Dipole Moment

The molecular dipole moment is the vector sum of all individual bond dipole moments in a molecule, indicating the overall polarity. In acetone, the dipole moment is primarily due to the polar C=O bond, as the symmetrical arrangement of the methyl groups cancels out their dipole contributions. Acetone has a moderate dipole moment, making it a polar molecule.