Organic Chemistry (CHM 221) Chapter 3

Chapter 3: Organic Molecules & Functional Groups

• This chapter covers organic molecules and their functional groups.
• Organic molecules contain carbon and hydrogen.
• Aliphatic hydrocarbons can be alkanes, alkenes, or alkynes.
• Aromatic hydrocarbons are cyclic and planar, exhibiting resonance stability.
• Benzene is the simplest aromatic hydrocarbon (C₆H₆).
• Functional groups are atoms or groups of atoms with unique chemical and physical properties attached to the carbon backbone of organic molecules.
• Heteroatoms are atoms other than carbon or hydrogen.
• Functional groups affect the molecule's geometry, physical properties, reactivity, and solubility characteristics.
• Functional groups with C=O bonds are important and include aldehydes, ketones, carboxylic acids, esters, and amides.
• Multi-functional molecules have multiple functional groups.
• The strength of intermolecular forces correlates with boiling and melting points. Molecules with stronger intermolecular forces have higher boiling and melting points.
• The type of intermolecular forces (van der Waals, dipole-dipole, and hydrogen bonding) depends on the structure and functional groups in a compound.
• Compounds such as butane will have a lower boiling point compared to butanol or other molecules with stronger bonds. Compounds with larger surface areas will exhibit stronger intermolecular forces and the bonds affect the solubility of compounds in water.
• Organic molecules are soluble in water if they possess a polar functional group and/or a minimal number of carbon atoms. Compounds with only a small number of carbon atoms and higher concentrations of polar functional groups such as hydroxyl or carboxyl are soluble in water.
• Solubility is affected by the "like dissolves like" principle. Polar substances tend to dissolve in polar solvents, and nonpolar substances dissolve in nonpolar solvents.
• Hydrophobic portions of molecules are insoluble in water, whereas hydrophilic portions are soluble.
• The size and shape of an organic molecule affect solubility characteristics and melting point characteristics. The more compact and symmetrical shape of a molecule tends to exhibit higher melting points and other solubility traits compared to those with more surface area or more chaotic structures.
• Functional groups determine the reactivity of organic molecules. Electrons in molecules are attracted to electron-poor/electrophilic areas in a molecule.
• Electrophilic sites have lower electron density.

Homework Problems

• Some homework problems are included in the chapter. Specifically, problems 3.12, 3.13, 3.15, 3.19, 3.20, 3.39, 3.50, 3.53, 3.57, and 3.58