Bromination of Cinnamic Acid PDF

# Assiut University Faculty of Pharmacy ## Department of pharmaceutical organic chemistry ### Pharmaceutical Organic Chemistry-1 For PharmD-1 Students 2024/2025 Section.4 ## Bromination of Cinnamic Acid ### General Equation The reaction of trans-cinnamic acid with bromine in acetic acid produ...

# Assiut University Faculty of Pharmacy ## Department of pharmaceutical organic chemistry ### Pharmaceutical Organic Chemistry-1 For PharmD-1 Students 2024/2025 Section.4 ## Bromination of Cinnamic Acid ### General Equation The reaction of trans-cinnamic acid with bromine in acetic acid produces 2,3-dibromo-3-phenylpropanoic acid. This reaction occurs with the addition of bromine to the double bond of cinnamic acid. The chemical equation for the reaction is as follows: `(E)`-Cinnamic acid + Br2/AcOH → 2,3-dibromo-3-phenylpropanoic acid ### Mechanism of the Reaction The mechanism of this reaction involves the formation of a bromonium ion intermediate. This intermediate is formed when the bromine molecule attacks the double bond of cinnamic acid. The bromonium ion is then attacked by a bromide ion to form the final product, 2,3-dibromo-3-phenylpropanoic acid. The reaction occurs in an anti-addition manner. This means that the two bromine atoms are added to the double bond on opposite sides of the molecule. ### Procedure The following procedure can be used to brominate cinnamic acid: 1. In a 250 ml stoppered conical flask, dissolve 0.5 g cinnamic acid in 2 ml glacial acetic acid. 2. Add 1 ml bromine/acetic acid solution and strongly shake the stoppered flask for 5 minutes. 3. Repeat step (two) four times with addition of 0.5 ml. 4. After the last addition, leave the flask for 30 min with frequent shaking. If the orange color of bromine disappears, add another 1 ml of bromine solution. 5. Add 50 ml water and few crystals of sodium bisulphite (NaHSO3) until the orange color disappears. 6. Filter the crude product, rinse with cold water until acetic acid odour disappear, press down to drain most of washing water, and finally leave on white paper for AIR drying. 7. Calculate the reaction yield and measure the melting point of the product. ### The Use of Sodium Bisulphite Sodium bisulphite is used to remove excess bromine from the reaction mixture. The reaction between sodium bisulphite and bromine is as follows: NaHSO3 + Br2 + H2O → NaHSO4 + 2HBr ### Safety Notes All procedures should be performed under a fume hood because bromine is highly toxic and corrosive. You must wear a lab coat, safety glasses, and gloves during this experiment. | Chemical | Hazard | CAS No. | |---|---|---| | Bromine | Dark, red-brown liquid with an irritating odor. Corrosive! Causes severe irritation or burns to eyes/skin/respiratory tract. Toxic! Also causes: dizziness, headache, coughing, and pulmonary edema. Strong oxidizer capable of igniting combustibles. | 7726-95-6 | | Glacial Acetic Acid | Colorless, hygroscopic liquid with a vinegar odor. Corrosive, causes severe burns to eyes/skin/respiratory tract. Chronic: skin may become darkened and thick, tooth enamel erosion, digestive disorders. Flammable. | 64-19-7 |