E2 Debromination of a Vicinal Dibromide

E2 debromination takes place by a concerted, stereospecific mechanism. Iodide ion removes one bromine atom, and the other bromine leaves as bromide ion. 

Use your models to show that only the trans isomer of stilbene is formed in this example by elimination through the anti-coplanar transition state. 

Zinc serves as a reducing agent in zinc/acetic acid dehalogenation. The reaction is heterogeneous (part solid and part liquid), with the actual reduction taking place at the surface of the metallic zinc. Zinc is oxidized from the 0 oxidation state to the +2 oxidation state, forming ZnBr2- 

The preceding example shows m o-l,2-dibromo-l,2-diphenylethane reacting with iodide ion to give rrani-stilbene. Show how the other diastereomer of the starting material gives a different stereoisomer of the product 

Show that the dehalogenation of 2,3-dibromobutane by iodide ion is stereospecific by showing that the two diastereomers of the starting material give different diastereomers of the product 

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Mechanism 7-1 Dehydrohalogenation by the E2 Mechanism 304 Mechanism 7-2 Stereochemistry of the E2 Reaction 306 Mechanism 7-3 E2 Debromination of a Vicinal Dibromide 310... 

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