CH 7-3: E2 Reaction - Stereospecific Elimination

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Presentation transcript:

CH 7-3: E2 Reaction - Stereospecific Elimination To form overlapping p-orbitals in the alkene product, the b-hydrogen and leaving group must be “anti-coplanar” in the transition state...……..”anti-elimination”. When the leaving group OR b-hydrogen is at a chiral center, the stereochemistry of elimination becomes important in determining the geometry of the alkene product.

Stereochemistry in the E2 Reaction: Elimination at Chiral Centers Look at the Neuman Projection for the alkyl halide: Note that if Ha is anti with Br, that the trans alkene forms.

Note that if Hb is anti with Br, that the cis (less stable) alkene forms.

SN1/E1 Substitution & Elimination Reactions in Cycloalkanes…non-Stereospecific

SN2/E2 Substitution & Elimination Reactions in Cycloalkanes…Stereospecific!!!