Absorption Spectra of Heterocyclic Compounds. I. Quinolinols and Isoquinolinols¹

Abstract

Absorption Spectra of Quinolinols and Isoquinolinols 2181 colored vanillic acid, whereas sulfur dioxide gave a white product in all cases.Reaction of Vanillin with Fused Potassium Hydroxide above 240°.-The same apparatus was used. A mixture of 165 g, of potassium hydroxide and 20 g. of water was heated to 225 °and with vigorous stirring was treated with 60 g. of vanillin in small portions at such a rate as to keep the resulting vigorous reaction from effervescing out of the crucible and to maintain the temperature at 225 °. Vanillin addition required approximately twenty minutes. The temperature was maintained at 225°for another five minutes, at which time all effervescence had ceased. A sample dissolved in water and acidified with hydrochloric acid gave only crystals of vanillic acid melting sharply at 207-208°. The mixture was heated to 240°for five minutes, which caused the fused mass to become more fluid. A sample at this point indicated only vanillic acid. No test for protocatechuic acid could be obtained by the very sensitive ferric chloride reaction. The temperature was then raised to 245-250 °, at which temperature effervescence again took place. After five minutes at 250°, a sample no longer gave a precipitate of vanillic acid when dissolved in water and acidified with hydrochloric acid. The fusion mixture was allowed to cool somewhat and was dissolved in 600 ml. of water. The alkaline solution was acidified with 6 N hydrochloric acid, giving an effervescent yellow solution which, upon standing, deposited colorless crystals. The crystals were filtered, washed with water, and dried at 105°to yield 36 g. (59%) of protocatechuic acid melting at 199-200°and not depressing the melting point of a mixture with authentic protocatechuic acid. Saturation of the acid filtrate with sodium chloride and extraction with ether yielded an additional 24 g. (40%) of protocatechuic acid melting at 195-200°. This experiment was repeated, the temperature being maintained just below 245°for thirty minutes. At that point no protocatechuic acid could be found. Raising the temperature to 245°caused reaction to set in and the temperature to rise to 255°. The mixture was worked up as above to yield 99% protocatechuic acid.Summary Caustic fusion of vanillin below 240-245°results in very high yields of vanillic acid free from protocatechuic acid. Fusion of vanillin above 240-245°y ields protocatechuic acid free from vanillic acid. The critical demethylation temperature varies somewhat with the alkali-vanillin ratio. Reaction of vanillin with strong alkali solution at elevated temperatures does not yield either of the acids.

Polarographic Reduction of 5-Hydroxyquinoline in Dimethylformamide

“…The reduction mechanism of 5-quinolinol at the droppong mercury electrode in DMF, therefore, is proposed as follows : For wave (H), •¬ (4) Hence, the reduction mechanism of 5-quinolinol at the dropping mercury electrode in aqueous medium is proposed as follows: For wave (B1),…”

Association of 6- and 8-Hydroxyquinolines with Aerosol-OT in Heptane: Competition with Dimerization of 8-Hydroxyquinoline

“…The absorption spectra of hydroxyquinolines are related to the absorption spectra of either 1-or 2-naphthol according to the position of the ϪOH group in the molecule (10). The absorption spectrum of 6-HQ is indeed quite similar to that of 2-naphthol.…”

Studies in detoxication. 65. The metabolism of quinoline. New metabolites of quinoline, with observations on the metabolism of 3-, 5- and 6-hydroxyquinoline and 2:4-dihydroxyquinoline

“…The former show a characteristic bifurcation in the absorption band occurring in the 320-360 m,u. region (Ewing & Steck, 1946;Steck, Ewing & Nachod, 1949) which is not found in the 2-quinolones. This bifurcation is, in fact, present in the spectrum of 4-quminolonyl-6-glucosiduronic acid (Smith & Williams, 1954).…”