Grignard synthesis — most versatile: RMgX + HCHO -> 1° (extends by 1C); RMgX + R'CHO -> 2°; RMgX + R'COR" -> 3°; RMgX + ethylene oxide -> 1° (extends by 2C). Hydroboration-oxidation: R-CH=CH2 + BH3 -> trialkylborane; then H2O2/NaOH -> RCH2CH2OH (anti-Markovnikov, syn addition, 1° alcohol). Reduction: LiAlH4 reduces aldehydes, ketones, esters, acids all to alcohols. NaBH4 reduces only aldehydes and ketones (milder, selective). Acid-catalysed hydration: Markovnikov addition — more substituted alcohol. Key comparison: hydroboration = anti-Markovnikov (1°); acid hydration = Markovnikov (2°/3°).