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Explain the given basicity order in aqueous medium: (CH_(3))_(2)overset(* *)(N)H(2^(@))gtCH_(3)overset(* *)(N)H_(2)(1^(@))gt(CH_(3))_(3)overset(* * )(N)(3^(@)) |
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Answer» Solution :Basic strenght of amines in aqueous MEDIUM depends on TWO factors: (1) Increased electron density on the N + atom MAKES an amine moer basic. So considering the +I effect of differect number of alkyl groups on the N - atom, the basic strenght of amines should follow the order:  (2) Again, basicity of an amine increases as stabilisationof the conjugate acid, through solvation, increases. The conjugate acid of primary amine attains maximum stability through intermolecular H - bond formation with three molecules of water, while the conjugate base of teriary amine attains minimum stablisation through such H - bond formation with only one molecule of water.  Thus on the BASIS of stability of the conjugate acids, the basic strenght of amins should follow the order: `CH_(3)-NH_(2)gt(CH_(3))_(2)NHgt(CH_(3))_(3)N` As a consequence of these two opposite orders of basicty practically we FIND the given sequence of basicity in aqueous medium : `(CH_(3))_(2)overset(* *)(N)H(2^(@))gtCH_(3)overset(* *)(N)H_(2)gt(CH_(3))_(3)overset(* *)(N)H(3^(@))` |
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