2051-65-2Relevant academic research and scientific papers
Sulfonation and sulfation in the reactions of the chloro- and dichlorophenols, 3-fluorophenol and (2,3-, 2,4- and 3,4-dichlorophenoxy)acetic acid with concentrated aqueous sulfuric acid and sulfur trioxide
Wit, Peter de,Cerfontain, Hans
, p. 121 - 124 (2007/10/02)
The chloro- and dichlorophenols have been sulfonated with sulfuric acid and with SO3 in aprotic solvents.In the sulfonations with concentrated aqueous sulfuric acid, the sulfonic acid isomer distribution is determined mainly by the ortho- and para-directing and activating effect of the hydroxy substituent; this is also the determining factor in the aprotic sulfonations using up to 1.0 equiv of SO3.Upon using larger amounts of SO3, the sulfonation isomer distribution is increasingly determined by additional sulfonation of the corresponding phenyl hydrogen sulfate, of which the -OSO3H substituent is deactivating and mainly para- (and further ortho-) directing.The sulfuric acid sulfonation of (2,3-, 2,4- and 3,4-dichlorophenoxy)acetic acid leads to the exclusive formation of the 4-, 6- and 6-sulfonic acid, respectively.
Sulfonation of chloro- and dichloroanisoles with concentrated aqueous sulfuric acid and sulfur trioxide. Demethylation of chloroanisolesulfonic acids in sulfuric acid systems
Wit, Peter de,Cerfontain, Hans
, p. 418 - 425 (2007/10/02)
The nine chloro- and dichloroanisoles have been sulfonated with sulfuric acid.The observed sulfonic acid isomer distributions are determined mainly by the ortho- and para-directing effect of the methoxy substituent.In the reaction with sulfuric acid, the initially formed chloro- and dichloroanisolesulfonic acids are demethylated to give the corresponding phenolsulfonic acids.Demethylation occurs only in those cases where the methoxy substituent is sterically hindered by an o-chloro and/or o-sulfo substituent.Reaction of 2,3- and 3,5-dichloroanisole with fuming sulfuric acid yields initially the 4,6- and 2,4-disulfonic acids, respectively.The disulfonic acids are converted to the corresponding hydrogen sulfates either by direct sulfodemethylation or by protodemethylation followed by subsequent sulfation.The 2,3-dichloro-4,6-disulfophenyl hydrogen sulfate cyclizes to the 1,3,2,4-benzodioxadithiin 2,2,4,4-tetraoxide 4.The sulfonation of the chloro- and dichloroanisoles with SO3 in the solvents nitromethane or CCl3F leads only to sulfodeprotonation.
Aromatic Sulphonation. Part 91. The Sulphonation of Anisole, Phenol, Phenyl Methanesulphonate, Potassium Phenyl Sulphate, and a Series of Methyl-, Bromo-, and Chloro-substituted Anisoles and Phenols in Concentrated Aqueous Sulphuric Acid
Cerfontain, Hans,Lambrechts, Hans J. A.,Schaasberg-Nienhuis, Zwaan R. H.,Coombes, Robert G.,Hadjigeorgiou, Panicos,Tucker, Geoffrey
, p. 659 - 668 (2007/10/02)
The (homogeneous) sulphonation of a number of aromatic ethers and alcohols, viz. anisole (1), 3-methyl- (2), 4-methyl- (3), 2-bromo- (4), 4-bromo- (5), 2-chloro- (6), and 4-chloro-anisole (7), phenol (8), 2-methyl- (9), 3-methyl- (10), 4-methyl- (11), 4-bromo- (12), 2-chloro- (13), and 4-chloro-phenol (14), phenyl methanesulphonate (15), and potassium phenyl sulphate (16) in concentrated aqueous sulphuric acid at 25.0 deg C has been studied, and rates and isomer distributions have been determined.The sulphonation is first-order in the aromatic substrate, and from the rate measurements it is concluded that the species undergoing sulphonation in the phenyl ring is an unprotonated substrate species.In the lower acid concentrations the sulphonating entity is H3SO4(1+).With increasing sulphuric acid concentration there is a gradual change-over in the sulphonating entity from H3SO4(1+) to H2S2O7.The acid concentrations of equal rate contribution by the two entities for anisole and phenol are 87 and 90 +/- 1percent, respectively.Sulphonation on the oxygen atom (i.e., sulphation) does not occur.The o/p-ratios for (1) and (8) do not vary over the studied sulphuric acid range of 75-90percent H2SO4.Partial rate factors for the 2- and 4-position of (1) and (8) are reported.The very low partial rate factors for the 4-substitution of (1) and (8) and the observed extreme suppression and compression of the reactivities of the substrates (1)-(14) are ascribed to hydrogen bonding of the substrates with the acidic solvent species present.It is tentatively suggested that the relatively high contents of sulphonation ortho to -OR with anisole (36percent) and phenol (48percent) are due to specific complexation of the substrates with the sulphonating electrophile.
