Nitrating Methyl Benzoate: Electrophilic Aromatic ... - Franklin College

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Nitrating Methyl Benzoate: Electrophilic Aromatic Substitution Introduction: The purpose of this experiment is to synthesize methyl nitrobenzoate from methyl benzoate, concentrated HNO3, and concentrated H2SO4 via an electrophilic aromatic substitution reaction. The product will then be isolated and recrystallized using 95% ethanol. Following recrystallization, melting point and infrared spectrum will be used to identify and characterize the product of the reaction. Regiochemistry of the product will also be determined. Materials Used: 50-mL beaker 50-mL graduated cylinder 400-mL beaker marking pen Hirsch funnel with tubing microspatula 25-mL Erlenmeyer flask 3 Pasteur pipets, with latex bulb 125-mL Erlenmeyer flask 3 pipets, 1-mL, with rubber bulb glass stirring rod sand bath 10-mL graduated cylinder support stand utility clamp 2 test tubes, 15 x 125-mm Reagents and Properties: Substances Formula Weight Quantity g/mol Moles Used Mole Ratio Melting Point °C Boiling Point Density °C Methyl benzoate 136.15 0.55 g 4.039 x 10 -3 1 to 1 113 – 115 N/A N/A Methyl nitrobenzoate 181.13 product N/A 1 to 1 78 – 80 N/A N/A Conc. Nitric acid 63.01 0.5 mL 1.192 x 10 -2 N/A N/A 121 1.5027 g/mL Conc. sulfuric acid 98.08 1.6 mL 3.0 x 10 -2 N/A N/A N/A 1.841 g/mL Ethanol, 95% 46.07 2-3 mL N/A N/A N/A N/A N/A Reaction and its Mechanism: Overall Reaction: O C Methyl benzoate OCH3 HNO3 H2SO4 NO2 O C Methyl m-nitrobenzoate OCH3 + H2O + H2SO4
Mechanism: Procedure: .. O N .. H O Nitric Acid O C O - .. .. O N O + Nitrating Methyl Benzoate: Electrophilic Aromatic Substitution OCH3 + H O SO3H Sulfuric Acid NO2 H + - O O C H OCH3 SO3H + H O N O O - .. .. - O N + + SO3H O O NO2 O C Methyl m-nitrobenzoate OCH3 + H2SO4 + H2O Part 1 – Preparing the Ice-Water Bath and Chilled Water Place equal volumes of ice and tap water into a 400-mL beaker so that the beaker is approximately 75% full. Then, prepare chilled water for parts three and four of this experiment by pouring approximately 30 mL distilled or deionized water into a 125-mL Erlenmeyer flask. Place the flask into the ice-water bath. Part 2 – Preparing the Nitrating Solution Label two 15 x 125-mm test tubes “nitric acid” and “sulfuric acid”, respectively. Transfer 0.5 mL concentrated nitric acid into the tube labeled “nitric acid.” Then, transfer 0.6 mL concentrated sulfuric acid into the tube labeled “sulfuric acid”. Chill both the test tubes with the acids in them in the ice-water bath for 15 minutes. Then, use a Pasteur pipet to very slowly add the cold sulfuric acid drop by drop into the cold nitric acid. Swirl the reaction mixture after every three drops are added. After adding all the sulfuric acid to the nitric acid, allow the nitrating solution to stand in the ice-water bath for 10 minutes. Part 3 – Nitrating Methyl Benzoate Place approximately 0.55 g methyl benzoate into a 25-mL Erlenmeyer flask and add 1.0 mL concentrated sulfuric acid. Clamp the flask containing the mixture to a support stand. Lower the flask into the ice-water bath for 5 minutes, being sure to prevent the bath water from entering the reaction flask. After the 5 minutes are up, use a Pasteur pipet to slowly add the nitrating solution in the test tube to the Erlenmeyer flask containing the methyl benzoate and sulfuric acid. After all the nitrating solution has been added, allow the mixture to stand in the ice-water bath for 30-45 minutes. Make sure you swirl the flask every 5 minutes. After the 30-45 minutes are up, add 10 mL chilled water to a 50-mL beaker. Slowly and carefully add the cold reaction mixture, with stirring, to the chilled water. Then, allow the chilled solution to stand 5-10 minutes to complete crystal formation. Part 4 – Isolating, Purifying, and Characterizing the Product Filter the reaction mixture via vacuum filtration. Wash the crystals with approximately 10 m L of chilled water in order to remove any residual acid. Then, allow your product to air dry in the filter tunnel for 10 minutes. Then, put your product crystals into a 10-mL Erlenmeyer flask and add 1 mL of 95% ethanol. Swirl the flask to mix. Heat the flask in a sand bath until the crystals are in solution and the solution boils. Boil the solution for a couple minutes, then remove the flask from the sand bath and allow it to cool to room temperature. Add approximately 0.5 mL ice-cold ethanol to the flask and swirl to loosen the crystals. Then filter the crystals using vacuum filtration. Allow the product to dry in the filter funnel for a couple days. Then, weigh your product and record its mass.
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Nitrating Methyl Benzoate: Electrophilic Aromatic ... - Franklin College

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