Two isomeric ketones, 3-pentanone CH3CH2COCH2CH3 and 2-pentanone CH3COCH2CH2CH3 can be distinguished by I2/NaOH. The name of the reaction is iodoform reaction and is given by compounds containing methyl keto group CH3CO
We can also use NaSO3H to distinguish 3-pentanone and 2-pentanone.