Why does Mn(III) undergo disproportionation reaction easily ?

Explanation

Mn(III) is highly unstable as it is clear from its very `E_(Mn^(3+)//Mn^(2+))^(@)` value (+1.57 V). As such, it undergoes disproportionation reaction as follows:
`2Mn^(3+)(aq) to Mn^(2+)(aq)+Mn^(4+)(aq)`