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Alkene bromination is one in which a dihalide such as Cl2 or Br2 is added to a molecule after breaking the carbon to carbon double bond.
Typology: Lab Reports
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Objective: In this experiment you will learn how to synthesize vicinal dihalides by brominating a solid alkene with pyridinium tribromide to produce a chiral vicinal dibromide. The solid product will be isolated by vacuum filtration. To verify the reaction went to completion, the product will be characterized using the silver nitrate test and verifying its melting point.
Alkene Bromination Procedure
Run the silver nitrate test on the product.* Record observations. In a small test tube, add a small amount of the product – roughly the same amount that you would use for the melting point. Add ~1 ml of ethanol. Swirl or stir the mixture to get it to dissolve. (If the sample does not dissolve, consult an instructor.) Once the sample has dissolved, add an equal volume of 1% AgNO 3 in ethanol solution. The test is positive if the solution becomes cloudy or tiny particulates are observed. *Caution: AgNO 3 will stain your fingers and clothing black. You may want to put a rubber stopper on the test tube before swirling the mixture, so that you do not inadvertently get AgNO 3 on your fingers.
Dispose of chemicals in the halogenated waste container. Clean and return all glassware and equipment. Post Lab:
Determine which compound you produced based on your starting material and the melting point of your product. Record your determination. (See Table 1 Below.)
Determine % Error for the melting point of your product.
Determine theoretical yield and % yield. ( Use your exact initial mass to determine theoretical yield .) Show sample calculations.
Tabulate your results in your lab book.
In your conclusion, discuss the success of the reaction based on the results of the melting point and the AgNO 3 chemical test. If there were any problems, make suggestions for how they could be avoided if you were to redo the experiment. . Table 1: Molar Masses and Melting Points of Reactants and Products Substance Molar Mass (g/mole) MP (oC) trans-cinnamic acid 148.16 133 trans-stilbene 180.25 124 2,3-dibromo- 3 - phenylpropanoic acid 307. (±)- threo 94 (±)- erythro 203 (±)-1,2-dibromo-1,2-diphenylethane 340.07 110 meso - 1,2-dibromo-1,2-diphenylethane 340.07 238 ________________________________________________________________________________________________________________________________________________________________________________________