Sodium Hypochlorite Pentahydrate in Organic Synthesis and Beyond

Sodium hypochlorite pentahydrate (NaOCl·5H 2 O) has emerged as a practical and versatile oxidizing reagent for modern organic synthesis. Compared with conventional aqueous sodium hypochlorite solutions, NaOCl·5H 2 O exhibits high active chlorine content, reduced excess sodium hydroxide, improved reproducibility, and enhanced reactivity under mildly acidic to neutral conditions. This review summarizes recent advances in NaOCl·5H 2 O‐mediated chemistry reported after previous reviews published in 2017 and 2020. Representative applications include alcohol oxidation, oxidative C─C bond cleavage reactions, oxidation of organosulfur compounds, synthesis of hypervalent iodine reagents, synthesis of three‐membered heterocycles, alkene functionalization reactions, and other oxidative transformations. Particular attention is given to the unique reactivity of NaOCl·5H 2 O, which often differs significantly from that of conventional aqueous hypochlorite systems. Recent studies have also demonstrated applications of NaOCl·5H 2 O beyond synthetic organic chemistry in fields such as semiconductor processing, environmental chemistry, and analytical science. These studies highlight the unique potential of NaOCl·5H 2 O as a practical solid‐state oxidant for modern chemistry.