1. Molecular bromine gives slightly better yields compared to pyridinium tribomi
ID: 482588 • Letter: 1
Question
1. Molecular bromine gives slightly better yields compared to pyridinium tribomide. However, using pyridinium tribromide also generates pyridine hydrobromide as a side product while molecular bromine generates no side products. What advantages are there to using pyridinium tribromide? What alternative methods exist for bromination? Provide 2 examples not mentioned in this lab
2. ) A researcher performs the reaction above starting with 0.101 g of the 1-Methylcyclohexene, 0.350 g of pyridinium tribromide, and 2.00 mL of acetic acid. Show all of your work for credit.
a.) What is the limiting reagent?
b.) What is the theoretical yield?
c.) If the researcher obtains 0.240 g of pure product, what is the percent yield?
Explanation / Answer
Liquid bromine is a hazardous substance due to its, volatile nature . it can cause severe buring of skin and eyes. Also it is diddifult to weigh due to the reasons state before. Pyridinium tribromide is a solid and easy to waigh out. It is less hazardous to skin and eyes. Also reaction with Br2 requires a chlorinated solvent like CCl4 which are known carcinogenic. Reaction with Pyridinium tribromide occurs in ethanol which is a green solvent.
Other reagents could be : N-bromo succinamine (allylic bromination), NaBrO3 + H2SO4
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1-methyl cyclohexane + Pyridine tribromide + Acetic acid -----> 1,2 dibromo -1-methyl cyclohexane
0.101g 0.35g 255.98g/mol
0.101g/96.17g/mol 0.35/319.122g/mol
=0.00105 mol =0.00109 mol
1-methylcyclohexene is the limiting reagent.
1 mol product is obtained from 1 mole starting materia.
Moles of product = 0.00105 mol = 0.00105 mol *255.98g/mol =0.268g
% yield = 0.24*100/0.268 = 89.6 %
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