Question

I need some help with an alkene bromination lab.

These are the directions:

For this assignment, the target compound that you should synthesize is anti-2,3-dibromo-butane. This is a stereospecific electrophilic alkene addition reaction. Examine the product to determine the location of the new functionality. Keep in mind the bromonium ion intermediate and the consequences of its structure. The nucleophile again attacks in a manner that controls the stereochemistry of the product.

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***I need to know what materials, solvent, and reagent to combine to produce anti-2,3-dibromo-butane.***

The things that I have to choose from for the starting materials are buta-1,3-diene, 2-butene, cyclohexene, and 1-hexene. Which of these should I use?

Also, I will use Et2O as a solvent, but should I use HCl, H2SO4, or another compound as a reagent?

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*** I also need some help answering some questions:***

1. How long did it take to finish the reaction?

2. What are the TLC values (Rf) for (a) Starting Materials: (b) Products:

3. Write a mechanism for this reaction:

Answer 1

You should star twith 2-butene, since it will form the "anti" form, the double bond will be in the middle, meaning that it will be readily to react and form the next "shape"

You will need the Bromine, of course (Br2)

You require CCl4 as a catalyst. Avoid using acids

1. How long did it take to finish the reaction?

Typically, depending on conditios (but I assume you are using Standard conditions) about 20 minutes

2. What are the TLC values (Rf) for

(a) Starting Materials --> nonpolar, therefore Rf value must be High if using nonpolar solvent as mobile phase and polar statoinary phase. The same is tru for Br2 since it is also nonpolar

(b) Products: --> will be slighlty polar, so they will run along the mobile phase having a higher Rf value.

3. Write a mechanism for this reaction: