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Arrange the following : In increasing order of basic strength : (a) Aniline, p-nitroaniline and p-toluidine (b) C_(6)H_(5)NH_(2), C_(6)H_(5)NHCH_(3), C_(6)H_(5)CH_(2)NH_(2). |
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Answer» Solution :(a) The electron-donating groups increase while the electron-withdrawing groups decrease the basic strength of amines. Therefore, p-nitroaniline is the weakest base followed by aniline while p-toluidine is the strongest base. THUS, basicity increase in the order : `"p-nitroaniline "LT " aniline "lt " p-toluidine. "` (b) In `C_(6)H_(5)NH_(2)" and "C_(6)H_(5)NHCH_(3)`, N is directly attached to the benzene ring. Therefore, the lone pair of electrons on the N-atom is delocalised over the benzene ring. Therefore, both `C_(6)H_(5)NH_(2)" and "C_(6)H_(5)NHCH_(3)` are weaker bases than `C_(6)H_(5)CH_(2)NH_(2)`. DUE to +I-effect of the `CH_(3)` GROUP, `C_(6)H_(5)NHCH_(3)` is a stronger bases than `C_(6)H_(5)NH_(2)`. Thus, basic strength increases in the order : `""C_(6)H_(5)NH_(2) lt C_(6)H_(5)NHCH_(3) lt C_(6)H_(5)CH_(2)NH_(2)` |
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