Chem bio cc 4

• Organic molecules that make up living things aren't flat, lifeless structures but have 3D shapes
• Cartesian coordinate system


  System with x, y, and z axes used to plot 3D molecular structures
• Understanding 3D molecular shapes helps understand how structure affects function
• VSEPR theory explains 3D molecular shapes based on electron pair geometry
• VSEPR electron-pair geometries used in organic chemistry

  • Linear
  • Trigonal planar
  • Tetrahedral
• Molecular shape


  Describes how atoms in a molecule relate to each other, ignoring lone pairs
• Orbital hybridization


  Mixing of atomic orbitals to produce hybrid orbitals that explain 3D molecular shapes
• sp3 hybridization


  Mixing of 1 s orbital and 3 p orbitals to produce 4 hybrid orbitals
• sp2 hybridization


  Mixing of 1 s orbital and 2 p orbitals to produce 3 hybrid orbitals
• sp hybridization


  Mixing of 1 s orbital and 1 p orbital to produce 2 hybrid orbitals
• Sigma bonds are formed by direct overlap of orbitals pointing at each other
• Pi bonds are formed by sideways overlap of p orbitals
• Trigonal planar geometry


  Arrangement of atoms around a central carbon with double bonds
• Linear geometry


  Arrangement of atoms around a central carbon with triple bonds
• Oxygen can be sp3 hybridized in single bonds or sp2 hybridized in double bonds
• Orbital hybridization and valence bond theory were key to determining the structure of DNA
• Isomers


  Molecules with the same molecular formula but different arrangements of atoms
• Constitutional (structural) isomers


  Isomers with the same atoms but different atom-to-atom connections
• Geometric isomers

  Isomers with the same atoms and connections but different spatial arrangements
• Molecules with double bonds can have geometric isomers due to lack of free rotation
• Understanding 3D molecular structures is key to understanding chemical reactions and life