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JEE Advanced levelSingle correct optionDifficulty 3 of 3g2097

Arrange in decreasing order of basic strength using pKaH values (piperidine 11.1, pyridine 5.2, pyrimidine 1.3, pyrrole $- 3.8$ ): piperidine, pyridine, pyrimidine, pyrrole.

Apyrrole > pyrimidine > pyridine > piperidine
Bpyridine > piperidine > pyrimidine > pyrrole
Cpiperidine > pyridine > pyrimidine > pyrrole
Dpiperidine > pyridine > pyrrole > pyrimidine

Answer: C

pKaH values 11.1 > 5.2 > 1.3 >

- 3.8

. Piperidine has an sp

^{3}

N; pyridine an sp

^{2}

N; pyrimidine has a second electron-withdrawing N; pyrrole's lone pair is part of the aromatic sextet (it protonates on carbon).

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