Why aqueous solution of methyl amine reacts with Iron(III) Chloride to form ppt. iron(III) hydroxide?
Aqueous methylamine reacts with ferric chloride to precipitate hydrated ferric oxide:
Due to the +I effect of-CH3 group, methylamine is more basic than water. Therefore, in water, methylamine produces OH- ions by accepting H+ ions from water.
CH3-NH2 + H2O CH3-NH3+ + OH-
Ferric chloride dissociates in water to form Fe3+ and Cl- ions.
Then, OH- ion reacts with Fe3+ ion to form precipitate of hydrated ferric oxide.
Fe3+ + 6OH- Fe2O3.3H2O
Hydrated ferric oxide