CHEM C11: Disproportionation Reactions

Today we’re covering:

  • Disproportionation reactions
    • Chlorine with water
    • Chlorine with aqueous sodium hydroxide

Let’s go!


What is Disproportionation?
Simultaneous oxidation & reduction of a species in a reaction.

Let’s take a look at a few examples of disproportionation in halides, & compare the oxidation states of the halogen before & after the reaction.


Chlorine with water
Chlorine reacts with water to form hydrochloric acid & chloric (i) acid

Cl2 (g) + H2O (l) → HCl (aq) + HClO (aq)

Species Cl2 HCl HClO
Oxidation state of chlorine 0 -1 +1

Cl is both oxidised (into HClO) AND reduced (into HCl)!


Chlorine with cold, aqueous sodium hydroxide (15°C)
Cl2 (g) + 2NaOH (aq) à NaCl (aq) + NaClO (aq) + H2O (l)

Species Cl2 NaCl NaClO
Oxidation state of chlorine 0 -1 +1

Cl is both oxidised (into NaClO) AND reduced (into NaCl)!


Chlorine with hot, aqueous sodium hydroxide (70°C)
Cl2 (g) + 6NaOH (aq) à 5NaCl (aq) + NaClO3 (aq) + H2O (l)

Species Cl2 NaCl NaClO3
Oxidation state of chlorine 0 -1 +5

Cl is both oxidised (into NaClO3) AND reduced (into NaCl)!

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