Synthesis and Nitration of Acetanilide - Lab Report

Synthesis and Nitration of Acetanilide Materials From the Chemicals Hood: Week 1: Acetic anhydride Aniline From the Stockroom (Blue Bin): Week 1: ½” pea-sized stirbar Stirbar retriever Week 2: Glacial acetic acid Concentrated sulfuric acid 50/50 Nitric acid/ sulfuric acid solution Ethanol Sodium bicarbonate aqueous solution (squirtbottle) Week 2: 1” stirbar Stirbar retriever 9 cm large Buchner funnel This is another two-step experiment and takes two weeks. The first step is acetylation of aniline to form acetanilide. This is done the first week. The second step is nitration of acetanilide. You will do that reaction the second week. You will determine which isomer of nitroacetanilide you formed using melting point, infrared, and NMR spectroscopy. Procedure – Preparation of Acetanilide Place an ice bath on top of the stir plate in the hood. In the ice bath place a 50-mL Erlenmeyer flask containing 10 mL of acetic anhydride and a magnetic stir bar. Turn the stirring on but keep the heat OFF. Add 10 mL of aniline (CAUTION: see Safety Note 1) 1 mL at a time over 10 minutes. Pour the reaction mixture into a beaker containing a 100 mL of cold water. If a solid does not form immediately, scratch the walls of the beaker with a glass rod for a few minutes. Vacuum filter the crystals and allow them to dry until the next lab period. At that time, determine the melting point, IR, and NMR of the product. Procedure – Nitration of Acetanilide Place 6.5 g of acetanilide in a 125-mL Erlenmeyer flask, add 10 mL of glacial acetic acid (CAUTION: strong irritant), and warm the flask on a steam bath until the acetanilide dissolves. Cool the flask in an ice bath for one minute (if premature crystallization occurs, rewarm the flask); then add 10 mL of cold, concentrated sulfuric acid (the solution will become very viscous). Keep the flask in the ice bath. Chill 10 mL of a mixture of HNO3/H2SO4 (this has been prepared for you and is in a bottle in the hood) in a 50-mL Erlenmeyer flask in an ice bath. Carefully place a magnetic stirring bar in the flask containing acetanilide and place it, in the ice bath, on the stir plate; turn the stirring on. When both solutions are cold, slowly add the HNO3/H2SO4 solution, 1 mL per minute using a pipet, to the acetanilide solution. Keep the reaction flask in an ice bath. Stir the reaction mixture carefully during addition. After the reaction is completed, allow the reaction flask to stir at room temperature for 30 minutes. Pour the reaction mixture into a 250 mL beaker containing 100 mL of cold tap water. Using a large Buchner funnel, filter the heavy lemon-yellow precipitate with vacuum. Press out as much aqueous acid from the filter cake as possible with the clean bottom of a 50-mL beaker while suction is being applied (CAUTION: see Safety Note 2). The precipitate is voluminous; use care in transferring it to the Buchner funnel or a substantial amount of product will be lost. Transfer the filter cake to a clean 250-mL beaker, and add 100 mL of cold water. Stir the mixture and refilter using vacuum. Wash the beaker with two 30-mL portions of cold water and pour the water onto the filter cake. Finally, wash the filter cake with an additional 50 mL of cold water. Press the filter cake with a spatula or clean beaker bottom as before to remove as much water as possible. The crude product can be purified by recrystallization from 30 mL of ethanol in a 125 mL Erlenmeyer flask. Heat IN a steam bath to dissolve the product. (The crude product dissolves very slowly, even with heating; avoid using an excess of solvent.) Determine the yield, melting point, IR, and NMR. Use this data to determine which isomer of nitroacetanilide you have. Record this in your notebook. SAFETY NOTE 1 Aniline is highly toxic and may be fatal if swallowed, inhaled, or absorbed through the skin. Aniline vapor is mildly irritating to the eye, and in liquid form it can be a severe eye irritant and cause corneal damage. Based on tests with laboratory animals, aniline may cause cancer. Aniline should be handled in areas with adequate ventilation and skin exposure should be avoided by the wearing of proper safety equipment (gloves). SAFETY NOTE 2 Nitro compounds are toxic and can be absorbed through the skin. Wear gloves while preparing nitroacetanilide.