Final answer:
The most reactive compound towards β-elimination reaction is 2-bromo-2-methylbutane due to the bromine being attached to a tertiary carbon, providing a more stable transition state.
Step-by-step explanation:
The compound that is most reactive towards β-elimination reactions among 2-bromopentane, 2-bromo-2-methylbutane, and 1-bromopentane is 2-bromo-2-methylbutane. This is due to the fact that β-elimination reactions favor more substituted alkyl halides, where the leaving group (such as a bromine atom) is located at a carbon atom that is connected to more carbon atoms.
The increased number of carbon substituents stabilizes the transition state during the reaction, making the β-elimination process proceed more readily. In 2-bromo-2-methylbutane, the bromine atom is connected to a tertiary carbon, which is attached to three other carbons. This tertiary carbon compared to a secondary or primary carbon, as seen in 2-bromopentane and 1-bromopentane respectively, will provide a more favorable condition for the elimination reaction to occur.