The opposite of disproportionation is a chemical reaction called comproportionation or synproportionation. In this type of reaction, two reactants containing the same element but with different oxidation numbers come together to form a compound with an intermediate oxidation number. Unlike disproportionation, where one reactant undergoes both oxidation and reduction, comproportionation involves the combination of two reactants to form a single compound.
To understand comproportionation better, let’s consider an example involving the element chlorine. Chlorine can exist in two oxidation states, -1 and +1, depending on the compound it is present in. Disproportionation of chlorine would involve a reaction where one chlorine atom is oxidized and another is reduced. For instance, in the reaction between chlorine gas (Cl2) and sodium hydroxide (NaOH), chlorine is reduced to chloride ions (Cl-) while being oxidized to hypochlorite ions (ClO-) simultaneously:
Cl2 + 2NaOH → NaCl + NaClO + H2O
In contrast, comproportionation of chlorine would involve the combination of two different chlorine compounds to form one compound with an intermediate oxidation state. For example, if we mix hydrochloric acid (HCl) and sodium hypochlorite (NaClO), chlorine undergoes comproportionation:
HCl + NaClO → NaCl + H2O + Cl2
In this reaction, chlorine in HCl has an oxidation state of -1, while in NaClO it is in an oxidation state of +1. The chlorine atoms combine to form chlorine gas (Cl2) with an oxidation state of 0. This reaction represents comproportionation as it involves the formation of a compound (Cl2) with an oxidation number intermediate between the two reactants.
Comproportionation reactions are not limited to chlorine and can occur with other elements as well. The key feature is the combination of two reactants with different oxidation numbers for the same element, resulting in the formation of a compound with an intermediate oxidation state.
The opposite of disproportionation is comproportionation or synproportionation. It involves the combination of two reactants with different oxidation numbers for the same element, leading to the formation of a compound with an intermediate oxidation state. This type of reaction is distinct from disproportionation, where one reactant undergoes simultaneous oxidation and reduction.