Addition of Hydrogen Bromide to 1-Hexene

Purpose To determine the regiochemistry of the polar addition of H-Br to an alkene. 

Concentrated hydrobromic acid (47-49%) is a highly corrosive and toxic material. Working at a hood, measure out the amount of acid required and avoid inhaling its vapors. Use latex gloves when transferring the acid between containers. If the acid comes in contact with your skin, flood the affected area immediately and thoroughly with water and rinse it with 5% sodium bicarbonate solution. 

Quaternary ammonium salts are toxic substances and can be absorbed through the skin. Should they accidentally come in contact with your skin, wash the affected area immediately with large amounts of water. 

If a flame must be used in the distillation step, be certain that all joints in the apparatus are well lubricated and tightly mated because 1-hexene and the solvents used, particularly petroleum ether, are highly flammable. Flameless heating is preferred. 

Preparation Sign in at www.cengage.com/login to answer Pre-Lab Exercises, access videos, and read the MSDSs for the chemicais used or produced in this procedure. Review Sections 2.4, 2.8, 2.9, 2.11,2.13, 2.17, 2.19, 2.21, 2.22, and 6.4. 

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Several of the procedures in this chapter involve addition reactions characteristic of alkenes. Two of them, the addition of hydrogen bromide to 1-hexene (Sec. 10.5) and of borane to a-pinene (Sec. 10.8), represent examples in which both the reagent and the alkene to which it is adding are unsymmetrical. Consequently, identifying the products from these reactions provides a means of testing whether a Markovnikov or an anti-Markovnikov mode of addition has occurred. 

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