Write a test to differentiate between pentan-2-one and pentan-3-one.

Explanation

Pentan-2-one is methyl ketone (i.e., contains the grouping `CH_(3)CO`) and hence undergoes Iodoform test on treatment with `I_(2)//NaOH` to give yellow ppt. of iodoform. In contrast, pentan-3-one is not a methyl ketone and hence does not give yellow ppt. of `CHI_(3)` on treatment with `I_(2)//NaOH`
`underset("Pentan-2-one")(CH_(3)CH_(2)CH_(2)-overset(O)overset(||)(C)-CH_(3)) underset(("Iodoform test")) overset(I_(2)//NaOH)to underset("Yellow ppt.")(CHI_(3))+underset("Sod. butanoate")(CH_(3)CH_(2)CH_(2)COONa)`
`underset("Pentan-3-one")(CH_(3)CH_(2)-overset(O)overset(||)(C)-CH_(2)CH_(3)) overset(I_(2)//NaOH)to ` No. yellow ppt. of `CHI_(3)` .