Spectra and photolysis of the 1‐oxides of the pyridinecarboxylic acids and pyridinecarboxamides

Abstract

The ultraviolet absorption spectra of aqueous and alcoholic solutions of the pyridinemono‐carboxylic acids and amides, of the vicinal pyridinedicarboxylic acids, and of the 1‐oxides of these compounds, were measured and qualitatively interpreted. The photolysis of the 1‐oxides in aqueous solution resulted principally in their deoxygenation. Photolysis of picolinamide 1‐oxide also gave a rearrangement product, 1‐formyl‐2‐pyrrolecarboxamide. The photolyses of the 2‐ and 4‐monosubstituted 1‐oxides were somewhat faster than those of the 3‐substituted 1‐oxides. The experimental results are discussed in terms of possible hydrogen‐bonding effects.

The photochemistry of the N-oxide function

“…Furthermore, 2,6-dicyanopyridine IVoxide reaches a 12% yield of photodeoxygenation in dichloromethane,82 and yields of about 20% are observed when the carboxyl or carboxamide group are present. 144 From polyphenylpyridine IV-oxides yields between 10 and 29% have been reported.85 Aza substitution is also effective. Thus, while pyrimidine IVoxides, in which the second nitrogen atom has little electronic effect, do not differ appreciably from pyridine IV-oxides, with at most some percent of deoxygenation,15'77,80'84 pyridazine and pyrazine IV-oxides are photodeoxygenated in much higher yields (Table XIV).…”

Nicotinamide complex of silver(III) with expanded coordination number

“…AgCl precipitation experiments show that the reduction of silver is a two- was not found. The presence of nicotinamide N-oxide was also confirmed by its UV absorbance maximum at 308 nm where it has an extinction coefficient ε = 10 2.7 [21].…”

Phthalic acid and pyridine dicarboxylic acids as catabolic analogs

“…Oxygenation of the ring nitrogen is also biochemically possible [11]. N-oxides of pyridine compounds often show additional UV absorption peaks or shoulders, and/or shifts towards longer wavelengths, as compared to the parent compound [12]. Quinolinic acid N-oxide has an absorption maximum at 307 nm [12], close to a peak observed in the product(s) of 2:3-PDCA oxidation by Strain OP-1.…”