| Abstract: | Solid state infrared curves (O-H and C-H stretching region) are given for 5, n-dihydroxyflavones, where n is 2′, 3′, 4′, 6, 7 and 8. In chloroform solution spectra of 3,5-dihydroxyflavone and 3-hydroxy-5-methoxyflavone, the 3-OH stretching band appears at 3400 and 3334 cm?1, respectively, indicative of a stronger hydrogen bond in the latter substance. Solid state and solution carbonyl bands are presented for twenty-six flavone derivatives which contain a hydroxyl, methoxyl or acetoxyl group at the 5-position. The solution spectra (dioxane or carbon tetrachloride) of fourteen flavone derivatives containing a free 5-hydroxyl group show carbonyl bands at 1655±2 cm?1. Eleven flavones in which the 5-hydroxyl is blocked (carbon tetrachloride solution) give spectra with flavone carbonyl bands at 1653±3 cm?1. The high resolution chloroform solution spectrum of 3, 5-dihydroxyflavone possesses a multi-peaked carbonyl band with midpoint at 1641 cm?1. The chloroform solution spectrum of 3-hydroxy-5-methoxyflavone has a very strong band at 1616 cm?1, with shoulder at 1646 cm?1. Spectral data of this and a previous paper support the postulate that in 4′-hydroxyflavone the flavone carbonyl oxygen is the donor atom in an intermolecular hydrogen bond. Certain details of synthesis, and analytical data, are given for 3, 5-dihydroxyflavone. |
