Summary And Reaction Maps

Chapter 2 Summary & Reaction Maps

Chapter 2 covers alkanes and cycloalkanes: how to name them, how their shapes and energies vary, and their core reactions.

Nomenclature: Name straight and branched alkanes; apply cyclo prefixes; give substituents the lowest set of locants.
Physical trends: Boiling point rises with chain length and drops with branching; alkanes are nonpolar and water-insoluble.
Conformations: Newman projections show staggered vs eclipsed (anti < gauche < eclipsed in energy). Cyclohexane chairs minimize strain; axial/equatorial positions flip on ring flip, and bulky groups prefer equatorial.
Reactivity: Alkanes are relatively inert but combust and undergo free-radical halogenation (initiation, propagation, termination). Product distribution follows radical stability (3° > 2° > 1°).

Alkane → Alkyl halide: Radical halogenation (X₂, hν).
Alkyl halide → Alkene: E2 elimination (strong base).
Alkyl halide → Alcohol/Ether/Amine: Substitution routes (SN1/SN2; preview of later chapters).
Alkane → CO₂ + H₂O: Combustion (excess O₂).

Can you draw anti/gauche Newman projections and pick the lowest-energy conformer?
Can you identify axial vs equatorial positions after a chair flip?
Can you predict the major product in a chlorination vs bromination of an alkane?

Naming + conformations set the stage for understanding stability and reactivity.
Radical halogenation is the main functionalization of alkanes; selectivity follows radical stability.
Conformational analysis underpins later chapters (stereochemistry, eliminations).