(I) Iodoform test is given by ethanal.
CH3−CHO+I2+NaOH→CHI3+HCOONa
So, I2/NaOH is an oxidising agent.
(II) KMnO4 is an oxidising agent which oxidises aldehydes to acids.
CH3−CHO+KMnO4H+−−→CH3−COOH
(III) When a freshly prepared solution of Tollen's reagent i.e. ammoniacal silver nitrate solution, is added to aldehydes and warmed, a bright silver mirror is produced due to the formation of silver metal. The aldehydes are oxidised to their corresponding carboxylate anions.
CH3−CHO+2[Ag(NH3)2]++3OH−+H2O→CH3−COO−+2Ag+4NH3+2H2O
(IV) LiAlH4 is a reducing agent.
CH3−CHO+LiAlH4→CH3CH2OH
(V) NaBH4 is a reducing agent.
CH3−CHO+NaBH4→CH3CH2OH
(VI)CH3−CHO+NH2−NH2NaOH−−−−→CH3−CH3+N2
Here, reduction occurs. So, NH2−NH2/NaOH is a reducing agent.