To separate a mixture of benzoic acid and fluorene, we are going to use an acid-base extraction technique. Most carboxylic acids are insoluble or slightly soluble in water, but they are highly soluble in dilute aqueous sodium hydroxide because the organic acid reacts with the base and produces carboxylate ions, a polar species. In a mixture of a carboxylic acid and an organic compound, the acid may be selectively removed from an organic solvent by extracting with a dilute NaOH solution. After separating the organic and aqueous layers, the carboxylic acid may be recovered from the aqueous solution by adding HCl, which causes precipitation of the carboxylic acid. Draw two structures below.