Compounds containing Nitrogen

Statement I:$\mathrm{CH}_3\mathrm{NH}_2$ is more basic than $\mathrm{NH}_3$ but $\mathrm{C}_6\mathrm{H}_5\mathrm{NH}_2$ is less basic than $\mathrm{NH}_3$.Explanation:Methylamine $(\mathrm{CH}_3\mathrm{NH}_2)$ :The $-\mathrm{CH}_3$ group is electron donating ( + I effect), which increases the electron density on nitrogen, making it more basic than ammonia.Aniline ( $\mathrm{C}_6\mathrm{H}_5\mathrm{NH}_2$ ):The lone pair on nitrogen gets delocalized into the benzene ring through resonance, reducing its availability to accept a proton.So aniline is less basic than ammonia.Hence, Statement I is correct. Statement II:The order of basic strength of amines in aqueous phase follows the order$(\mathrm{C}_2\mathrm{H}_5)_3\mathrm{N}>(\mathrm{C}_2\mathrm{H}_5)_2\mathrm{NH}>\mathrm{C}_2\mathrm{H}_5\mathrm{NH}_2.$Let's check this:In the aqueous phase, basic strength is influenced by two factors:+ I effect (electron donating alkyl groups increase basicity)Solvation effect (stabilization of the conjugate ammonium ion)In aqueous solution, the solvation effect is strong for primary $>$ secondary $>$ tertiary amines, because primary amines can form more hydrogen bonds.However, the +1 effect increases as we move from primary $\longrightarrow$ secondary $\longrightarrow$ tertiary.The combined effect in aqueous phase gives the observed order:Secondary amine $>$ Primary amine $>$ Tertiary amineThat is:$(\mathrm{C}_2\mathrm{H}_5)_2\mathrm{NH}>\mathrm{C}_2\mathrm{H}_5\mathrm{NH}_2>(\mathrm{C}_2\mathrm{H}_5)_3\mathrm{N}$But the statement says the order is:$(\mathrm{C}_2\mathrm{H}_5)_3\mathrm{N}>(\mathrm{C}_2\mathrm{H}_5)_2\mathrm{NH}>\mathrm{C}_2\mathrm{H}_5\mathrm{NH}_2$ This is incorrect in aqueous medium.