Electrophilic Aromatic Substitution

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In the nitration of benzoic acid, the mixture of HNO3 plus H2SO4 and benzoic acid dissolved in H2SO4 was combined. Combining HNO3 and H2SO4 is an acid-base reaction which will be shown in the reactions to be shown. During the dissolution of benzoic acid solids, some unexpected reactions visibly occurred. White slimy and sticky ppts start to form which was unexpected from the reaction mixture. Both mixtures are placed in an ice bath and when it was combined, the temperature of 0-10C was maintained. as the HNO3-H2SO4 solution was added, the white ppts seen was lessen but is still present in the mixture. The solution was visibly yellow in color. After addition, it was allowed to cool to room temperature. The mixture was added to crushed ice and then mixed. Until there was visible granular ppts forming in the mixture. The ppt settled at the bottom and the liquid in the mixture is light yellow in color. The mixture was filtered thru suction and the ppt was washed with cold dH2O. Here is the acid-base reaction between nitric acid and sulfuric acid to form the nitronium ion. Bronsted base bronsted acid conj. Acid +HSO4(conj base) Based on bronsted definition, an acid is a proton donor and a base is a proton acceptor. Sulfuric acid is a stronger acid than nitric acid so it is the one to be deprotonated. While the resulting product of the base is the conjugate acid and the product of the acid is the conj base. (chang, R. 2005. Chemistry. 8th ed. McGraw-Hill companies, Inc.) Although sulfuric acid served as the acid in the reaction, it is also the catalyst in the over-all reaction. Water, attached to N, is good leaving group so it is eliminated to form the nitronium ion. The ppt was further recrystallized and purified. It was first dissolved in hot dH2O and then hot gravity filtration was performed. Many insoluble substances were isolated and cream in color. The

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