Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate.

The synthesis of 3,5-lutidine N-oxide dehydrate, 1, was achieved in the synthesis route of 2-amino-pyridine-3,5-dicarboxylic acid. Ochiai first used the methodology for non-substituted pyridines in 1957 in a 12 h process, but no X-ray suitable crystals were obtained. The substituted ring used in the methodology presented here clearly influenced the addition of water molecules into the asymmetric unit, which confers a different nucleophilic strength in 1. The X-ray suitable crystal compound 1 was possible due to the stabilization of the negative charge in the oxygen by the presence of two water molecules where the hydrogen atoms donate positive charge into the ring; such water molecules serve well to construct a supramolecular interaction. The hydrated molecules may be possible for the alkaline system that is reached by adjusting the pH to 10. Importantly, the double methyl substituted ring and a reaction time of 5 h, makes it a more versatile method and with wider chemical applications for future ring insertions.

Crystal structure of 3,5-di-methyl-pyridine N-oxide dihydrate.

In the title compound, also known as 3,5-lutidine N-oxide dihydrate, C7H9NO·2H2O, the N-O bond is weakened due to the involvement of the O atom as an acceptor of hydrogen bonds from the two water mol-ecules of crystallization present in the asymmetric unit. Fused R35(10) ring motifs based on O-H⋯O hydrogen bonds form chains in the [010] direction, which are further connected by weak C-H⋯O inter-molecular contacts. As a result, the lutidine mol-ecules are stacked in an efficient manner, with π-π contacts characterized by a short separation of 3.569 (1) Šbetween the benzene rings.