Alkali-Induced Disproportionation of Molecular Halogens

The reaction of halogen molecules (X = Cl, Br, 1) with cold aqueous alkali to yield hypo-halite (OX ) and halide (X ) may be viewed as a classic inorganic 8 2 displacement, rather similar to the reaction with pyridine mentioned above  

X2 -b 2 NaOH NaX + NaOX + H2O The halogen-halogen bond breaks easily because of its weakness  

Hydroxide then deprotonates the hypohalous acid to produce a hypohalate anion  

With hot alkaU, however, the same reactants give different products. The hypohalite anions, the initial products of the reaction, disproportionate on warming to halate (XO ) and halide (X , X = Cl, Br, I)  

This is not an easy mechanism to envision. Multiple negatively charged hypohalite anions must somehow come together to generate the products. The simplest mechanism involves an SN2-type attack on a hypohalite oxygen, with halide as the leaving group  

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