A researcher was attempting to make an alkyl bromide via electrophilic addition
ID: 775310 • Letter: A
Question
A researcher was attempting to make an alkyl bromide via electrophilic addition to an alkene. She asked her research assistant to carry out the synthesis using freshly distilled alkene. The assistant placed the appropriate mass of 3-methyl-1-butene in the flask then he added HBr. He isolated the product and ran a proton NMR spectrum on it. The spectrum that appeared on the screen was not the one the assistant was expecting. Below is the spectral data for the product.
Draw the structure of the product that was characterized by proton NMR.
A researcher was attempting to make an alkyl bromide via electrophilic addition to an alkene. She asked her research assistant to carry out the synthesis using freshly distilled alkene. The assistant placed the appropriate mass of 3-methyl-1-butene in the flask then he added HBr. He isolated the product and ran a proton NMR spectrum on it. The spectrum that appeared on the screen was not the one the assistant was expecting. Below is the spectral data for the product. singlet @ 0.9 with integration ratios 6:2:3, respectively Draw the structure of the product that was characterized by proton NMR. 1.75, triplet @ 1.84, quartet @Explanation / Answer
Well, you start out with an alkene and react it with HBr in the presence of dietyl ether. As long as you have your starting material drawn right, you are going to get the anti-markovnicov reaction in which the double bond opens up and grabs the H of the HBr. You are then left with a carbocation. But before the Br can come onto the cation, if you look closely, a hydride shift can be performed to a make a more stable carbocation. Then the Br can come on. You should get 1-bromo-1-methyl-butane. If you draw out the molecule you can see for a proton NMR you would get 6 singlets, 2 qaurtets , and 3 triplets.
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