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Arrange the following : In decreasing order of the pK_(b) values : C_(2)H_(5)NH_(2), C_(6)H_(5)NHCH_(3), (C_(2)H_(5))_(2)NH" and "C_(6)H_(5)NH_(2). |
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Answer» Solution :Due to delocalisation of lone pair of electrons of the N-atom over the benzene ring, `C_(6)H_(5)NH_(2)" and "C_(6)H_(5)NHCH_(3)` are FAR less basic than `C_(2)H_(5)NH_(2)" and "(C_(2)H_(5))_(2)NH`. Further, due to +I-effect of the `CH_(3)` group, `C_(6)H_(5)NHCH_(3)` is little more basic than `C_(6)H_(5)NH_(2)`. Among `C_(2)H_(5)NH_(2)" and "(C_(2)H_(5))_(2)NH, (C_(2)H_(5))_(2)NH` is more basic than `C_(2)H_(5)NH_(2)` due to GREATER +I-effect of the two `C_(2)H_(5)` GROUPS. The relative basic strength of these FOUR amines shows the order : `""(C_(2)H_(5))_(2)NH gt C_(2)H_(5)NH_(2) gt C_(6)H_(5)NHCH_(3) gt C_(6)H_(5)NH_(2)` As `pK_(b)` varies inversely as the basic strength, `pK_(b)` follows the order : `"" C_(6)H_(5)NH_(2) gt C_(6)H_(5)NHCH_(3) gt C_(2)H_(5)NH_(2) gt (C_(2)H_(5))_(2)NH` |
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