The E1 elimination reaction proceeds through a _________ .
A. concerted process
B. carbocation intermediate
C. polarized transition state
To determine the correct answer, we need to understand the mechanism of the E1 elimination reaction.
The E1 elimination reaction, also known as the unimolecular elimination reaction, occurs in two steps: ionization and deprotonation. In the ionization step, a leaving group (usually a halogen or a sulfonate group) leaves the substrate, forming a carbocation intermediate. In the deprotonation step, a base abstracts a proton from an adjacent carbon to generate the double bond, resulting in the elimination product.
Now, let's analyze the options:
A) A concerted process: This option refers to a mechanism in which the reaction occurs in a single step, with simultaneous bond breaking and bond forming. However, the E1 elimination reaction occurs in two distinct steps, so option A is not correct.
B) Carbocation intermediate: As mentioned earlier, the E1 elimination reaction involves the formation of a carbocation intermediate. The leaving group leaves, generating a carbocation that serves as a reactive species before deprotonation occurs. Consequently, option B is correct.
C) Polarized transition state: A transition state represents an intermediate stage between the reactants and products during a chemical reaction. Although transition states are usually polarized, option C does not accurately describe the E1 elimination reaction. The primary reason is that a polarized transition state typically implies a more concerted or bimolecular reaction mechanism, rather than the unimolecular E1 elimination reaction.
To summarize, option B is correct. The E1 elimination reaction proceeds through a carbocation intermediate.