Where Did All the bpy Go? – Synthesis, Crystal and Molecular Structure of 4-Nitropicolinic Acid Monohydrate

Abstract

The conversion of 2,2′-bipyridine (bpy) to 4,4′-disubstituted derivatives is commonly achieved by a route involving preparation of the N,N′-dioxide and subsequent nitration with HNO₃/H₂SO₄. The yields in the latter reaction are of the order of 50% and we now show that a competing ring oxidation process leads to the formation of 4-nitropicolinic acid. The solid state structure of the monohydrate of 4-nitropicolinic acid is reported, which exhibits a series of interesting packing motifs arising from hydrogen bonding networks.

Keywords:

• 2,2-Bipyridine
• Nitration
• Oxidation
• Crystal structure

Acknowledgements

We thank the Universities of Basel and Birmingham and the Swiss National Science Foundation for support of this work.