SYNTHESIS OF p-BROMOANILINE
In this experiment, p-bromoaniline was synthesized in three steps starting from aniline. Since the amino group of aniline is a strong activator of aromatic ring, direct bromination is impractical (equation 1). In order to make a desired product, amino group needed to be protected as the acetamide which also maintained ortho and para position but slowed down the rate of reaction (equation 2). Slow reaction rate would increase the possibility of obtaining the para-position product (equation 3). The acetamide can be hydrolyzed back to the amine (equation 4). This strategy of protection and deprotection is a very important tool in organic chemistry, especially in multi-step synthesis. Equation 1:
Table of Physical data:
|Compound |Molecular |Amount |Density (g/ml) |Moles |Melting point |Boiling point | | |Weigh (g) | | | |m.p. oC |b.p oC | |[pic] |93.128 |2.0 ml |1.021 |0.0219 |-6.2 |184 | |Aniline | | | | | | | |HCl concentration |36.460 |2.0 ml |0.909 |0.0498 |-114.24 |-85.06 | |Water |18.015 |50 ml |0.909 |--- |0 |100 | |[pic] |129.588 | |1.221 | |198 |245 | |Anilinium chloride | | | | | | | |[pic] |102.089 |2.56 ml |1.08 |0.0270 |-73.1 |139 | |Acetic anhydride | | | | | | | |[pic] |82.034 |3.3147 g |1.45 |0.0404 |58 | | |Sodium acetate | | | | | | | |[pic] |135.165 |0.6718 g |1.219 |0.00197 |114.3 |304 | |Acetanilide | | | | | | |
• Bromine is very corrosive. Wear gloves when using it. • p-Bromoaniline is harmful if inhaled or absorbed through the skin • Aniline is highly toxic. It is possible mutagen, sensitizer, and readily absorbed through the skin.
1. Dilute 2.0 ml of concentration HCl in 50 ml of water in a 125 ml flask, then add 2.05g (2.0 ml) of aniline. 2. Stir the mixture until the aniline completely dissolves. HCl and aniline reacts forming anilinum chloride. (A reaction for this step was included in your report). 3. Add 2.77g (2.56 ml) of acetic anhydride, stir until it is dissolves and immediately pour a solution of 3.3g of sodium acetate in 10 ml of water into the flask. 4. After complete addition, stir vigorously for 5 minutes, then cool in ice. Crystallization should occur. When no more crystals seem to form (5—10 minutes), vacuum filter the acetanilide, wash the crystals with small volumes of cold water and air dry for 5 minutes. 5. Pure acetanilide is usually obtained as white flakes. Recrystallize the obtained acetanilide from a minimum of hot water. Use 10 ml of water to start and increase the amount of water...