Lab 1: Alkene Addition: Bromination of (E)-stilbene
1. The purpose of the experiment was to perform an electrophilic addition reaction by using pyridinium tribromide to brominate (E)-stilbene and to identify whether it formed the meso- or racemic product through melting point analysis. 2. This is the mechanism for the bromination of (E)-stilbene. However, this is the mechanism for Br2 and in class we us Pyridinium Tribromide instead due to the difficulties associated with the handling of such a volatile chemical. The mechanisms are very similar though as both reactions prefer to form a three-membered ring intermediate.
3. Below is the reaction equation for the experiment and shows the possible identities for the product.
II. Key experimental details, observations, and results:
Table 1: Exactly how much of each reagent was used
| Amount added to flask
Glacial Acetic Acid
1. The 10mL round-bottom flask weighed 17.690g.
2. The flask was heated and stirred at ~95 C until the (E)-stilbene dissolved. 3. 4mL of cold Deionized water was run through the condenser. 4. After the addition of the deionized water the solution became a pale yellow. 5. The weight of the filter paper was .50g.
6. The weight of the final product plus the filter paper was .898g. 7. The weight of the final product was .398g.
B. Description of product:
-The final product was a pasty, weight powder. Even after it was dry, it was still difficult to get a sample into the capillary tube because the product kept sticking to the sides of the tube. This may not be a property of the compound though it’s possible it could be a result of incomplete drying. The melting point range of the product was 246-249 C. D. Weight and Percent Yield of Product:
-The weight of the final product is .898g - .5g = .398g...
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