ORGO lab Addition of HBr

ORGO lab Addition of HBr - Saaniya Contractor Dorothee...

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6/7/11 Dorothee Borchmann T/R 1pm Addition of HBr to 1-Hexene Abstract In this microscale experiment, hydrobromic acid was added to 1-hexene, an ionic addition, to see whether 2-bromohexane is produced according to Markovnnikov's rule or not. Through my experiment, I found that 2-bromohexene, was in fact produced according to Markovnikov's rule. This was confirmed by the silver nitrate test and the sodium iodide test. Introduction The purpose of this experiment was to determine the regiochemistry of the addition of H-Br to the unsymmetrical hexene 1-hexene. This was done to specify whether this ionic reaction proceeds according to Markovnikov's rule to produce 2-bromohexane. This experiment is quite difficult to perform for several reasons: Common alkenes are generally immiscible with concentrated aqueous hydrombromic acid. Furthermore, the layers are sluggish if the layers are not mixed efficiently. H-Br is a strong acid that protonates water to produce a hydronium ion, H 3 O + , and a weaker acid that H-Br will not protonate the alkene rapidly as we would like in mild conditions such as those in this experiment. The presence of water in this experiment (from the aqueous H-Br) introduces the possibility of competing acid catalyzed addition of water to alkene. A solution to this problem would be using a quatenary ammonium salt to act as a transfer catalyst, such as tetrabutyl ammonium bromide and adding it to the mixture of aqueous H-Br and 1-hexene, which causes a separation of the aqueous and organic phase. Essentially, what the tetrabutyl ammomium bromide does is dehydrate the H-Br, making it more reactive to the alkene and making the addition more possible. Main Reaction
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ORGO lab Addition of HBr - Saaniya Contractor Dorothee...

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