(1) Organisch-chemischen Institut der Universität Mainz, Bundesrepublik Deutschland
Abstract:
The pK-values of the first and second degree of dissociation of 2.2-dihydroxy-5-methyl-3.5-dinitro-diphenylmethane, 2.2-dihydroxy-5-methyl-5-nitro-diphenylmethane and 2.2-dihydroxy-5.5-dimethyl-3-nitro-diphenylmethane were determined in aqueous solution at 25°C spectrophotometrically. Comparing the observed pK-values with those of 2-methyl-4.6-dinitrophenol, 2-methyl-4-nitrophenol, 2.4-dimethyl-6-nitro-phenol and 2.4-dimethylphenol, we found a decrease of the values of pK1 and an increase of pK2. We explain this by the formation of an intramolecular hydrogen bridge which stabilizes the anion of the half dissociated form. This assumption is supported by the UV spectra.Mit 3 Abbildungen