Question

Name the products obtained when the following reagents add to 2 -methyl-2-butene. (a) \(\mathrm{Cl}_{2}\) (b) \(\mathrm{I}_{2}\)

Short answer

Answer: The products obtained are 2,3-dichloro-2-methylbutane when Cl\(_2\) reacts with 2-methyl-2-butene, and 2,3-diiodo-2-methylbutane when I\(_2\) reacts with 2-methyl-2-butene.

Step-by-step solution

Write the structure of 2-methyl-2-butene

First, draw the structure of 2-methyl-2-butene. It is an alkene with four carbon atoms, with a double bond on the second carbon and a methyl group (CH\(_3\)) attached to the second carbon as well. Structure of 2-methyl-2-butene ``` CH3C(CH3)=CHCH3 ```

Electrophilic addition reaction with Cl\(_2\)

In the presence of chlorine Cl\(_2\), 2-methyl-2-butene undergoes an electrophilic addition reaction, where one Cl atom forms a bond to each of the carbons involved in the double bond, to give the corresponding halogenated product. The double bond is broken in the process.

Predict the product with Cl\(_2\)

When the Cl\(_2\) molecule approaches the double bond, the pi electrons in the double bond are attracted to Cl, causing the two Cl atoms to add to the 2-methyl-2-butene molecule. Since the second carbon atom in the double bond (C2) is tertiary while the third carbon atom (C3) is secondary, the tertiary carbon will form the bond with Cl to yield a more stable product. The final product when Cl\(_2\) adds to 2-methyl-2-butene is 2,3-dichloro-2-methylbutane: ``` CH3C(Cl)(CH3)CH(Cl)CH3 ``` (a) The product obtained when Cl\(_2\) adds to 2-methyl-2-butene is 2,3-dichloro-2-methylbutane.

Electrophilic addition reaction with I\(_2\)

Just like with Cl\(_2\), in the presence of iodine (I\(_2\)), 2-methyl-2-butene undergoes an electrophilic addition reaction, where one I atom forms a bond to each of the carbons involved in the double bond, to give the corresponding halogenated product. The double bond is broken in the process.

Predict the product with I\(_2\)

When I\(_2\) adds to 2-methyl-2-butene, the two I atoms will add to the second and third carbons in a similar fashion to the Cl\(_2\) addition. The tertiary carbon (C2) will form a bond with I due to its greater stability. The final product when I\(_2\) adds to 2-methyl-2-butene is 2,3-diiodo-2-methylbutane: ``` CH3C(I)(CH3)CH(I)CH3 ``` (b) The product obtained when I\(_2\) adds to 2-methyl-2-butene is 2,3-diiodo-2-methylbutane.