CHEM 211 Chapter Notes - Chapter 7.5-7.6: Elimination Reaction, Stereochemistry, Alkoxide
8 Dec 2016
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Chapter 7. 5: synthesis of alkenes via elimination reactions. Elimination reactions are very important for synthesizing alkenes. Two methods of alkene synthsis through elimination are: dehydrohalogenation of alkyl halides, dehydration of alcohols. Dehydrohalogenation = does best under the conditions that promote e2: these types of conditions include. 1. secondary or tertiary alkyl halides: to prevent substitution. 2. if it is a primary halide, use a bulky base: to prevent substitution. 3. high concentration of strong and non-polarizable base (ex. alkoxide: to prevent e1 or sn1. Etona/etoh and (t-buok/t-buoh) are types of bases for e2: they ful ll #1-3, ethoxide = etona, butoxide = t-buok. 5. use elevated temps: heat promotes elimination reactions, zaitsev"s rule. Formation of the more substituted alkene is favored with a small base. Zaitsev"s rule = when elimination gives a product that is more stable and more highly substituted, it follows zaitsev"s rule: more stable products form faster.
