Ethyl acetate halogenated phenols

Phenol in ethyl acetate was added dropwise to a solution of bromine (orBrCT) in ethyl acetate at 0-5C during 90min. to 2h. and excess halogen removed by sodium bisulphite to give 4-hromophenol. 

The retention characteristics of 29 aza-arenes (e.g., pyridine, acridine, quinoline, benz[a]acridine, and numerous substituted analogs) were studied on a diol column using a 97.5/2.5 iso-octane/ethanol mobile phase [611]. Dimethylbenz[a]acridine was least retained k < 3) and indole had the greatest retention (k > 9). The study also worked with 29 phenols (e.g., numerous alkyl-substituted phenols, nitrophenols, and halogenated phenols). They were studied in detail on the diol column using a 50/50 iso-octane/dichloromethane mobile phase. Appropriate selection of solvent composition provided baseline resolution of isomeric groups (e.g., dimethylphenols using hexane/ethyl acetate). 

The solvent used in these dimerization reactions dictates the activity of the catalyst. Besides benzene and dioxane, acetic acid [246,247], halogenated hydrocarbons [245,247], nitroderivatives [247], sulfones, tetrahydrofuran (THF), ethyl acetate, phenol, dimethylformamide, hydroquinone, catechol, benzyl alcohol, salicylic acid, anisole, and acetone have been used [247]. In solvents like benzene and chlorohydrocarbons and in highly polar solvents like dimethylsulfoxide and dimethylformamide, dimerization does not occur. The reaction proceeds in solvents containing oxygen atoms. The dissociative solvents like phenol and acetic acid show high solvent effect. In carboxylic acids the rate of dimerization decreases with an increase in pK . 

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