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Predict, giving reasons, the order of basicity of the following compounds in gaseous phase, (i) (CH_(3))_(3)N,(CH_(3))_(2)NH,CH_(3)NH_(2),NH_(3) (ii) C_(2)H_(5)NH_(2),(C_(2)H_(5))_(2)NH,(C_(2)H_(5))_(3),N,CH_(3)NH_(2) |
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Answer» Solution :DUE to +I-effect of the alkyl groups, the electron density on the N-atom of `1^(@),2^(@) and 3^(@)` AMINES is higher than that on the N-atom in `NH_(3)`. Therefore, all amines are more basic than `NH_(3)`. (i) In gaseous phase, solvation effect are absent and hence the relative basicity of amines depends only on the +I-effect of the alkyl groups. now since the +I-effect increases in going from `1^(@) ` to `2^(@)` to `3^(@)` amine, therefore, the relative basicity of amines decreases in the order: `3^(@)` aminegt`2^(@)` amine `gt1^(@)` amine. in other words, in the gaseous phase, the basicity of methylamines relative to `NH_(3)` decreases in the order: `(CH_(3))_(3)N gt (CH_(3))_(2)NH gtCH_(3)NH_(2)gtNH_(3)` (II) I the gas phase, solvent EFFECTS are absent and hence the relative basicity of amines depends only on the +I-effect of the alkyl groups. now the +I-effect of the `C_(2)H_(5)` group is more than that of `CH_(3)` group and the +I-effect increases as the number of alkyl groups increases, therefore, overall basicitiy of the four amines increases in the order: `CH_(3)NH_(2) lt CH_(2)H_(5)NH_(2) lt (C_(2)H_(5))_(2)NH lt (C_(2)H_(5))_(3)N` |
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