The sulfonation of a series of methylphenanthrenes (MPs) and two bromophenanthrenes with S03 in nitromethane has been studied at 0 °C. From the substitution pattern it is evident that steric factors play an important role. Substitution of the 4-and 5-H peri to the methyl does not occur, and that ortho to the 9-methyl is severely reduced. Provided that allowance is made for the steric factors, the positional order of substitution for monosulfonation of a given (methyl)phenanthrene is in agreement with that predicted by the localization energies, calculated by a simple Hückel MO treatment. The position of substitution of the second sulfo group is governed by two factors, viz., the positional localization energies of the starting MP (which will lead to symmetrical disulfonic acids) and the directing effect of the first (pyro)sulfonic acid group (leading to asymmetrical disulfonic acids). The latter factor is only apparent when the difference in localization energy for the positions of substitution under question of the starting MP are not too large. The formation of disulfonic acids with 2,4,5,7-and 3,4,5,6-TMP when 1 equiv of S03 is used is ascribed to a mixing-disguised substrate selectivity, as a result of the very high reactivities of both the given TMP and its monosulfonic acid toward S03.
Abstract. The protonation of phenol (2), 4-fluorophenol (3), phenyl methanesulfonate, potassium phenyl sulfate and the potassium 2-and -4-sulfonates of both phenol and anisole in concentrated aqueous sulfuric acid at 30°C has been investigated using 13C NMR spectroscopy. The results show that phenol and 4-fluorophenol are protonated predominantly on the oxygen atom. This protonation is governed by the HOa acidity function. The pKa of the oxonium ions of 2 and 3 are -6.40 k0.05 and -6.41 f0.05, respectively. The protonation of phenyl methanesulfonate occurs at acid concentrations > 100%. Potassium phenyl sulfate in 2 2 0 % H,SO, hydrolyses very rapidly to give phenol. The 2-a& 4-sulfonates of both phenol and anisole are protonated on both the -OR (R = H, Me) and the -SO,-groups; the sulfuric acid concentrations of half-protonation have been determined to be between 80.0 and 83.3% H'SO,, corresponding with pK,'s of the conjugate acids between -6.34 and -6.66 based on the H," scale.
Abstract. The ionization of the oxonium ions of phenol, anisole, 4-chloro-and 4-methyl-phenol and 4-bromo-, 4-fluoro-and 4-methyl-anisole in concentrated aqueous sulfuric acid has been investigated using UV spectroscopy at 25°C. The sulfuric acid concentrations at half-ionization are within the range 75.2 to 81.8% H,S04, corresponding with pK,'s between -5.87 and -6.52 based on the Hoa acidity function. The substituent effects on the ionization of PhO+H2 and PhO'HMe are small, the Hummet p values being 0.5 kO.1 and 0.9kO.1, respectively.
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