Elimination Problem 9

Description:

Problem

What would be the major product (alkene) obtained when the following alkyl halides react with NaOEt?

1. 1 − Bromo − 1 − methylcyclohexane

2. 2 − Chloro − 2 − methylbutane

3. 2,2,3 − Trimethyl − 3 − bromopentane

Solution

• Dehydrohalogenation is the reaction in which elimination of X and H atoms take place from α and β −carbons.

• When more than 1 β − hydrogen atoms are present, multiple alkenes can  be formed.

• The more stable alkene will be the major product.

1. 1 − Bromo − 1 − methylcyclohexane reacts with EtO⁻: two different alkenes are formed. The one with the maximum alkyl groups attached to the double bond is the most stable alkene and hence the major product.

2. When  2 − Chloro − 2 − methylbutane reacts with EtO⁻, two alkenes are formed. Major product will be the more stable alkene or the more substituted double bond.

3. When 2,2,3 − Trimethyl − 3 − bromopentane reacts with EtO⁻