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Organic Chemistry: Sn2E2 Reactions

Problems

The E2 Reaction

SN2 vs. E2

Problem :

Will compound X undergo an E2 reaction? State your reasoning.

Compound X will not undergo an E2 reaction. It has no β -hydrogens.

Problem :

Predict the product of the following E2 reaction. Assume that there is no rotation about the C-C bond.

Problem : Predict the major product of the following E2 reaction:

According to Saytzeff's rule, the major product will be the most substituted alkene.

Problem :

The large tert-butyl group locks the ring into its current conformation.

Using the molecular orbital theory, determine whether this molecule is a good candidate for the E2 reaction and explain why.

This conforomation of the molecule is not a good candidate for the E2 reaction. All three β -hydrogens are locked into a non-antiperiplanar conformation. Thus there will be no electron density to donate into the σ * C-Br antibond.

Let's see how the situation would change if the carbon-bromine bond had been in an axial instead of an equatorial conformation. In this case there would be antiperiplanar β -hydrogens, and E2 would be possible.

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