Chapter 22: Organic & Biological Molecules: Hydrocarbons, Polymers, Biomolecules

The study begins with alkanes, the simplest hydrocarbons composed entirely of single bonds between carbon and hydrogen atoms. Students learn systematic nomenclature rules for naming these saturated compounds, explore structural isomerism and how molecular geometry influences physical properties like boiling points and solubility patterns. The chapter then examines unsaturated hydrocarbons, including alkenes with carbon-carbon double bonds and alkynes with triple bonds, which exhibit significantly higher chemical reactivity and serve critical roles in industrial synthesis and manufacturing. Aromatic hydrocarbons, particularly benzene, are introduced with emphasis on resonance stabilization mechanisms and the electrophilic aromatic substitution reactions that define this compound class. The discussion transitions to hydrocarbon derivatives containing functional groups, including alcohols with hydroxyl groups, ethers with oxygen linkages, carbonyl-containing aldehydes and ketones, carboxylic acids as weak organic acids, esters formed from condensation reactions, and amines as nitrogen-based bases. Each functional group is examined for its characteristic chemical properties and reactivity patterns. The chapter then addresses polymers, including both synthetic materials such as polyethylene, polyester, and nylon used in modern manufacturing, and natural biopolymers including proteins and nucleic acids. Detailed attention is given to biological macromolecules essential to life: proteins are analyzed through amino acid building blocks connected by peptide bonds with multiple levels of structural organization; carbohydrates are presented as primary energy molecules ranging from simple sugars like glucose to complex polysaccharides such as starch and cellulose; lipids are discussed as hydrophobic molecules serving membrane functions and energy storage; and nucleic acids including DNA and RNA are explained as information-carrying polymers composed of nucleotide monomers held together by specific base-pairing interactions. This integrated approach helps students recognize how fundamental hydrocarbon chemistry escalates to extraordinary molecular complexity supporting life processes.