In organic chemistry an "alkene" is any compound that includes a so-called "double-bond" between carbon atoms, wherein two electrons pairs from each carbon (rather than one) bond the atoms together. When you add HBr (hydrogen bromide) to an alkene, it "breaks" the double bond by adding "H" (hydrogen) and "Br" (bromine) atoms to either side of it. According to a basic organic chemistry principle known as "Markinovkov's Rule," the location where Br attaches itself depends on whether or not peroxide is present during the addition--and you must add the peroxide before the HBr if you wish to add it at all.
- Beaker
- Dropper
- Hydrogen bromide
- Alkene
- Hydrogen peroxide (option)
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Instructions
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1
Pour your alkene into a beaker from the reagent shelf. Either your instructor or the text of your lab manual will specify the amount you need.
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2
Add a few drops of hydrogen peroxide to the beaker if you wish for the Br to attach to the so-called "end" carbon. In some cases your experiment will call for you to add HBr both with and without peroxide.
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3
Add the amount of HBr your instructor or experiment specifies to your alkene. It's important to add the HBr after you add peroxide (if your experiment calls for peroxide), because your HBr reacts instantly with alkenes--adding peroxide later will do nothing, as the reaction will have already completed.