AMINES60522.4The electron-donating amino group and the electron-withdrawing nitro group are directly conjugatedinp-nitroaniline. The planar geometry ofp-nitroaniline suggests that the delocalized resonance formshown is a major contributor to the structure of the compound.22.5The pKbof an amine is related to the equilibrium constant KbbypKblog KbThe pKbof quinine is thereforepKblog (1106)6the values of Kband pKbfor an amine and Kaand pKaof its conjugate acid are given byKaKb11014 andpKapKb14The values of Ka and pKafor the conjugate acid of quinine are thereforeKa1108andpKa14pKb146822.6The Henderson–Hasselbalch equation described in Section 19.4 can be applied to bases such asamines, as well as carboxylic acids. The ratio [CH3NH3] [CH3NH2] is given by The ionization constant of methylammonium ion is given in the text as 2
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