prelab 7

prelab 7 - Color impurities may also be removed via...

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John Goodson Creation of a Diphenylacetylene Carbon-Carbon Triple Bond by Bromine Addition and Elimination to an Alkene Introduction: In this experiment, a triple bond will be created by the addition of a bromine equivalent to the alkene, trans-Stilbene. The bromine will then be eliminated from the new molecule, Stilbene dibromide, via dihydrohalogenation by heating in a solvent with a strong base, KOH. A two-step reaction, the second step’s removal of hydrogen and halogen causes the formation of the triple bond. The first step, which occurs rapidly and in high yield, involves warming and mixing of the reagents to precipitate the reactant for the second step. Reflux of the precipitant in solvent with the KOH reagent will bring about dihydrohalogenation and create diphenylacetylene with its triple bond. Recrystallization in an ice bath and filtration will be used to separate the product.
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Unformatted text preview: Color impurities may also be removed via recrystallization from water and ethanol. Weight and yield calculations will be carried out, along with a measurement of the boiling point of the solid. The product will then be discarded and the experiment concluded. John Goodson Table of Reagents: Safety: Pyridinium hydrobromide perbromide, KOH, and glacial acetic acid can cause burns and should be handled carefully. Wear gloves and wash any spills with water. Add boiling chips when heating. Compound Amount Molecular Weight (g/mol) Mp( °C) Properties Trans-Stilbene 2.0 g 180.24 125 Alkene Pyridinium hydrobromide perbromide 4.0 g 319.86-Bromine source Stilbene dibromide-340.07 238 Intermediate Alkyl Halide Diphenylacetylene 178.22 61 Glacial acetic acid 40 mL Solvent KOH 1.5 g 86.18 Washing solution Ethylene glycol 20 mL 62.02-High-boiling solvent...
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prelab 7 - Color impurities may also be removed via...

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