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Tuesday, December 31, 2019

Pyridine is almost 1 million times less basic than piperidine? Why?


We know that if nitrogen is part of an aromatic ring, however, its basicity decreases markedly.  So in pyridine nitrogen is part of an aromatic ring hence its basicity is much more less than piperidine. The difference between the two lies in the fact that the nitrogen lone pair occupies an sp3- hybridized orbital in piperidine versus an sp2-hybridized one in pyridine. As we have noted on several occasions, electrons in orbitals with more s character are more strongly held than those with less s character. For this reason, nitrogen holds on to its unshared pair more strongly in pyridine than in piperidine and is less basic.

Cyclohexylamine amine is the stronger base than Aniline? Why?


We can say that aniline is a weaker base than cyclohexylamine because the electron pair on nitrogen of aniline is strongly held by virtue of being delocalized into the π system of the aromatic ring. The unshared pair in cyclohexylamine is localized on nitrogen, less strongly held, and therefore “more available” in an acid–base reaction.

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Tetrahydroquinoline amine is the stronger base than Tetrahydroisoquinoline? Why?



We can say that Tetrahydroisoquinoline  is a weaker base than Tetrahydroquinoline because the electron pair on nitrogen of Tetrahydroisoquinoline is strongly held by virtue of being delocalized into the π system of the aromatic ring. The unshared pair in Tetrahydroquinoline is localized on nitrogen, less strongly held, and therefore “more available” in an acid–base reaction.

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