Lab 8 - Synthesis of Diphenylacetylene Experiment # 8 Dan...

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Synthesis of Diphenylacetylene Experiment # 8 Dan Guerra Section: 6 TA: Yi and Luke 11/3/11
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Purpose: The purpose of this lab was to perform the synthesis of an alkyne (diphenylacetylene) in two steps: bromination followed by double dehydrohalogenation; with the product then further purified through recrystallization. The effectiveness of the experiment was tested through TLC, melting point, physical appearance, and percent yield was performed to assess the success, efficiency, and purity of the synthesis. Another purpose of the lab was to determine what the limiting reagent was. Results and Discussion: Compound Observed Melting Point (˚C) Theoretical Melting Point (˚C) Crude Diphenylacetylene 43-47 NA Recrystallized Diphenylacetylene 50-54 62.5 Compound Rf value Trans-stilbene 0.67 1,2-dIbromo-1,2-diphenylethane 0.52 Crude diphenylacetylene 0.67 Recrystallized diphenylacetylene 0.67 Compound: Part A Experimental mass (g) Mass of product (g) Theoretical yield (g) Molecular Weight (g/mol) Percent yield) Trans-stilbene (limiting reagent) 0.501 NA 180.25 Pyridinium tribromide 1.01 NA 318.84 1,2-dibromo-1,2- diphenylethane NA 1.02 0.945 340.05 107% Compound: Part B Reactant mass (g) Product mass (g) Theoretical yield (g) Molecular weight (g/mol) Percent yield 1,2-dibromo-1,2- diphenylacetylethane (Limiting reagent) 0.502 340.05 Potassium Hydroxide 0.25 56.11 Diphenylacetylene (recrystallized product) 0.01 0.26 178.24 3.9%
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For this experiment, the synthesis of diphenylacetylene was preformed in two steps: bromination, followed by double dehydrohalogenation. For the first step, trans- stilbene was dissolved in acetic acid and mixed with pyridinium tribromide, with the expected product being 1,2-dibromo-1,2-diphenylacetylethane. The using the product from the first step, 1,2-dibromo-1,2-diphenylacteylethane, it was then mixed with potassium hydroxide and triethylene glycol. The resulting crude product was recrystallized and filtered. To test the effectiveness of the experiment in producing diphenylactylene,
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This note was uploaded on 02/15/2012 for the course ORGO 101 taught by Professor Staff during the Fall '11 term at Syracuse.

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Lab 8 - Synthesis of Diphenylacetylene Experiment # 8 Dan...

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