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13.4     Arrange the following:

                (i) In decreasing order of the pKb 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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C_{2}H_{5}NH_{2}, and (C_{2}H_{5})_{2}NH are aliphatic amines so they are more basic than rest two compound. In ethylamine, there is only one electron donating group (+I effect) but in diethylamine, there is two electron donating group so the electron density is much higher than ethylamine.

In between C_{6}H_{5}NHCH_{3}, and C_{6}H_{5}NH_{2} they are the weak base because of delocalisation of lone pair electron in the benzene ring. Aniline is less basic than N-methylaniline(C_{6}H_{5}NHCH_{3},) due to the absence of an electron donating group. Thus the decreasing order of pKb values is-

C_{6}H_{5}NH_{2}>C_{6}H_{5}NHCH_{3}>C_{2}H_{5}NH_{2}>(C_{2}H_{5})_{2}NH

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manish

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