Draw orbital pictures of the pi bonding in the following compounds:
a. CH₃COCH₃
b. HCN

Verified step by step guidance

1. Step 1: Identify the pi bonds in each compound. For CH3COCH3 (acetone), the pi bond is between the carbon and oxygen in the carbonyl group. For HCN (hydrogen cyanide), the pi bond is between the carbon and nitrogen atoms.
2. Step 2: For CH3COCH3, draw the carbonyl group. The carbon atom is sp2 hybridized, forming a sigma bond with oxygen and two other sigma bonds with the methyl groups. The remaining p orbital on carbon overlaps with a p orbital on oxygen to form the pi bond.
3. Step 3: Represent the pi bond in CH3COCH3 using orbital pictures. Show the side-by-side overlap of the p orbitals on carbon and oxygen. Use MathML to depict the orbital overlap: $p-p$.
4. Step 4: For HCN, identify the hybridization of the carbon and nitrogen atoms. Carbon is sp hybridized, forming a sigma bond with hydrogen and another sigma bond with nitrogen. The remaining two p orbitals on carbon overlap with two p orbitals on nitrogen to form two pi bonds.
5. Step 5: Draw the orbital picture for HCN. Show the linear arrangement with the carbon and nitrogen atoms, and depict the side-by-side overlap of the p orbitals forming the pi bonds. Use MathML to represent the orbital overlap: $p-p$.

Key Concepts

Pi Bonding

Pi bonding occurs when the orbitals of adjacent atoms overlap sideways, forming a bond above and below the plane of the atoms. It is typically found in double and triple bonds, where one sigma bond is accompanied by one or more pi bonds. Pi bonds are less strong than sigma bonds due to the less effective overlap of orbitals.

Orbital Hybridization

Orbital hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals suitable for the pairing of electrons to form chemical bonds. In organic molecules, common hybridizations include sp3, sp2, and sp, which correspond to tetrahedral, trigonal planar, and linear geometries, respectively. Understanding hybridization helps predict molecular geometry and bonding properties.

Molecular Geometry

Molecular geometry refers to the three-dimensional arrangement of atoms within a molecule. It is determined by the number of bonds and lone pairs around the central atom, influencing the molecule's shape and reactivity. For example, acetone (CH3COCH3) has a trigonal planar geometry around the carbonyl carbon, while hydrogen cyanide (HCN) is linear due to sp hybridization.