Welcome to ChemZipper !!!: N,N,2,6-Tetramethyl aniline is more basic than N,N-Dimethyl aniline.Why ?

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N,N,2,6-Tetramethyl aniline is more basic than N,N-Dimethyl aniline.Why ?

 In case of N,N-Dimethyl aniline its dialkyl derivatives the NMe2group is coplanar with benzene ring.  So p-electron (lone pair) on N atom and pi orbitals are remain in the same plane. For this the p-electron on N-atom can delocalized via pi orbital in the benzene ring and its result the electron availability in para position is high and less available at nitrogen atom and hence less basic.

On the other hand , in case of N,N,2,6 tetramethyl aniline(2,6-dimethyl N,N-dimethyl aniline) having two bulky methyl group in ortho position of the benzene ring , the NMe2 group can not remain in the same plane. That is why the p-electron on N-atom cannot delocalized through pi orbital in para position. (due to steric inhibition of resonance)  It is localized at nitrogen atom Thus 2,6-Dimethyl aniline  derivative is more basic.

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