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3-Hydroxyisonicotinaldehyde (HINA), also known as 3-hydroxypyridine-4-carboxaldehyde, is a derivative of pyridine, with hydroxyl and aldehyde substituents. It has been studied as a simple analogue of vitamin B 6. In 2020, it was reported as having the lowest molecular weight of all dyes which exhibit green fluorescence. [2] [3]
The amide group can be involved in hydrogen bonding to other nitrogen- and oxygen-containing species.. The predominant solid state form is 2-pyridone. This has been confirmed by X-ray crystallography which shows that the hydrogen in solid state is closer to the nitrogen than to the oxygen (because of the low electron density at the hydrogen the exact positioning is difficult), and IR ...
It is an electrophilic source of oxygen that reacts with enolates and related structures, and thus can be used for alpha-hydroxylation of carbonyl-containing compounds. [3] Other reagents used for alpha-hydroxylation via enol or enolate structures include Davis oxaziridine , oxygen , and various peroxyacids (see Rubottom oxidation ).
The process is labor-consuming and inefficient: coal tar contains only about 0.1% pyridine, [63] and therefore a multi-stage purification was required, which further reduced the output. Nowadays, most pyridines are synthesized from ammonia, aldehydes, and nitriles, a few combinations of which are suited for pyridine itself.
1.509 at 20 °C Abbe number ... Table data obtained from CRC Handbook of Chemistry and Physics 44th ed. log 10 of Pyridine vapor pressure.
4-Pyridone exists a keto-enol tautomerism with its enol tautomer 4-hydroxypyridine. In solution, the keto tautomer is favoured, [4] and the enol tautomer only becomes important in very dilute solutions or solutions of non-polar solvents.
Chloro(pyridine)cobaloxime(III) is first reduced to Chloro(pyridine)cobaloxime(I) by sodium borohydride in alkaline solution, then an alkyl halide is added into the reaction mixture, and the desired Co-C bond is formed via a S N 2 reaction. This method can be used to produce cobaloximes containing a primary or a secondary alkyl substituent.
Pyridine N-oxide is five orders of magnitude less basic than pyridine: the pK a of protonated pyridine-N-oxide is 0.8. [7] Protonated derivatives are isolable, e.g., [C 5 H 5 NOH]Cl. [3] Further demonstrating its (feeble) basicity, pyridine-N-oxide also serves as a ligand in coordination chemistry.