Common features of E1 and E2 mechanisms Both E1 and E2 are elimination reactions with some common features. First, in both reactions, there is a loss of hydrogen and the leaving group, and the result is the formation of a … Read more
E1 reactions are regioselective and, just like in the E2 mechanism, the Zaitsev product predominates due to the higher stability of the more substituted alkene: Notice that in the reaction above, water was used as a weak base, … Read more
Check Also in Elimination Reactions: Elimination Reactions of Cyclohexanes General Features of Elimination The E2 Mechanism Regioselectivity of E2 Reactions: The Zaitsev and Hofmann Products Stereoselectivity of E2 Reactions Stereospecificity of E2 Reactions The E1 Mechanism Stereoselectivity of E1 Reactions … Read more
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
