Why does the rate of the E1 reaction depend only on the substrate?

Question

Ryan Andrews · Accepted Answer

Step 1 is the rate determining step (slow step) and therefore, we have only one reactant which is #R-X# and the #Rate = k[R-X]#.

The elimination reaction E1 from its name, the 1 means that it is a unimolecular reaction.

E1 reactions happen in two consecutive steps:

Step 1: Formation of the carbocation (#R-X# is the alkyl halide).
#" " " " " " ##R-X -> R^+ + X^-#

Step 2: Attack of the nucleophile.
#" " " " " " ##R^+ + Nu^(-) -> R' + HNu# where #R'# is an alkene.

Since the first step is bond breaking (needs energy) and the second step is bond formation (releases energy), therefore, step 1 is the rate determining step (slow step) and therefore, we have only one reactant which is #R-X# and the #Rate = k[R-X]#.

Here is a video about E1 and E2.

Madison Anderson · Answer

undefined The rate of the E1 reaction depends only on the substrate because the rate-determining step involves the unimolecular dissociation of the substrate to form a carbocation intermediate. The stability of the carbocation intermediate, which is primarily determined by the structure of the substrate, dictates the rate of the reaction. Therefore, factors such as the presence of electron-withdrawing or electron-donating groups on the substrate, the degree of substitution, and the stability of the resulting carbocation significantly influence the rate of the E1 reaction.