E1 reactions are stereoselective – that is, when a cis or a trans alkene can be formed, the trans isomer is generally the major product: This selectivity can be explained by simply comparing the stability of alkenes. Remember, … Read more
The E1 is a stepwise, unimolecular – 1st order elimination mechanism: The first, and the rate-determining step, is the loss of the leaving group, forming a carbocation which is then attacked by the base: This is … Read more
Consider these E2 elimination reactions. For both, the β hydrogens are on the right side of the Br, and as expected, that’s where the double bond appears in the product: So, no problems with the regiochemistry of these … Read more
E2 reactions are stereoselective. Let’s understand the meaning of this statement by looking at the following elimination reaction: Two stereoisomers are formed – a cis and a trans alkene. The trans alkene is the major product, and this … Read more
Zaitsev’s Rule Suppose you have this alkyl halide and need to determine all the products of an E2 reaction when it is treated with a strong base such as sodium ethoxide. Remember in E2 reactions, we’re first going … Read more
E2 is the most common elimination mechanism. The “2” indicates that both the alkyl halide and the base participate in the rate equation. This is somewhat similar to the SN2 mechanism: Notice that the beta hydrogen and the bromine … Read more
In this post, we will talk about the E2 and E1 elimination reactions of substituted cyclohexanes. Let’s start with the E2 mechanism. When the following substituted cyclohexane is treated with sodium ethoxide, an E2 elimination is expected to occur, as … Read more
