Here are two reactions that you have done in the laboratory. To what class of re
ID: 1067973 • Letter: H
Question
Here are two reactions that you have done in the laboratory. To what class of reactions do these two belong? Jack has synthesized the stilbene dibromide via reaction (1). He used 250 mg of trans-stilbene, and a solution of Bromine in methylene chloride and carried out the synthesis taking all the necessary precautions He ultimately obtained 287 mg of the product. What is the % yield of Jack's product? (Please show all the relevant calculations with units for full credit) Jill assisted Jack and has synthesized diphenylacetylene via reaction (2). She used 250 mg of meso-stilbene dibromide. 4 pellets of KOH and 2 mL of triethylene glycol (TEG) and carried out the synthesis taking all the necessary precautions. She ultimately obtained 87 mg of the product What is the % yield of Jill's product? (Please show all the relevant calculations with units for full credit)Explanation / Answer
(1) addition reaction - bromination
(b)
moles of trans stilbene = mass / molar mass = 250 * 10-3 / 180.25 = 0.00139 mol
From the given stoichiometric equation, 1 mol trans stilbene froms 1 mol stilbene dibromide
Then, 0.00139 mol trans stilbene should form 0.00139 mol stilbene dibromide.
Mass of stilbene dibromide (theoretical yield) = 0.00139 * 340.058 = 0.473 g. = 473 mg
But actual yield = 287 mg.
Thereofore, % yield = (287/473) * 100 = 60.7 %
(2) Elimination reaction - dehalogenation
moles of meso stilbene dibromide = 250 * 10-3 / 340.058 = 0.000735 mol
From the stoichiometric equation provided,
a mol meso stilbene dibromide gives 1 mol diphenyl acetylene
then, 0.000735 mol should give 0.000735 mol of product.
Mass of Product (theoretical yield) = 0.000735 * 178.24 = 0.131 g. = 131 mg
But actual yield = 87 mg.
Now, % yield = (87/131) * 100 = 66.4 %
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