: 180
Alkanes (CnH2n+2, sp3): Free radical substitution only. Unreactive under normal conditions. Combustion gives CO2 + H2O. Alkenes (CnH2n, sp2): Electrophilic addition is the characteristic reaction. Test with Br2/CCl4 (decolorizes) or KMnO4 (Baeyer's test). Key reagents: HX (Markovnikov), HBr/ROOR (anti-Markovnikov), BH3 then oxidation (anti-Markovnikov, syn), OsO4 (syn-diol), O3 (cleavage), mCPBA (epoxide). Alkynes (CnH2n-2, sp): Similar to alkenes but harsher conditions. Terminal alkynes are acidic (NaNH2 deprotonation). Selective reduction: Lindlar → cis, Na/NH3 → trans. Hydration: Hg2+/H+ → methyl ketone (Markovnikov), disiamylborane → aldehyde (anti-Markovnikov). Benzene (aromatic): EAS over addition to preserve aromaticity. Requires Lewis acid catalyst for halogenation. Directing effects control regiochemistry. Stability: aromatic >> conjugated > isolated > cumulated.