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

1 Answer
Sep 19, 2015

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]#.

Explanation:

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.