Ch7slides - Chapter 7: Alkenes: Reactions and Synthesis H C...

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1 Chapter 7: Alkenes: Reactions and Synthesis C C C C OH H C C H H C C OH X C C X X alcohol alkane halohydrin 1,2-dihalide C C X H halide alkene C C OH HO 1,2-diol C C halide C C O carbonyl C C alkene X Y + C C Y X Elimination Addition Electrophilic Addition Dehydrohalogenation: loss of HX from an alkyl halide to form an alkene + HBr Br H H H H H ether Br H H H + KOH EtOH (ethanol) H H + KBr + H 2 O
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2 Hydration: addition of water (H-OH) across a double bond to give an alcohol Dehydration: Loss of water (H-OH) from an alcohol to give an alkene + H 2 O OH H H H H H H + OH H H H H H + H 2 O H + Addition of Halogens (X 2 ) to Alkenes: 1,2-dihalides C C C C X X 1,2-dihalide alkene X 2 1,2-dibromide has the anti stereochemistry Bromonium ion intermediate controls the stereochemistry + Br 2 Br Br + Br Br not observed
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3 Halohydrin Formation C C C C OH X halohydrin alkene "X-OH" OH anti stereochemistry Br 2 , H 2 O + HBr Organic molecules are sparingly soluble in water as solvent. The reaction is often done in a mix of organic solvent and water using N-bromosuccinimide (NBS) as the electrophilic bromine source. DMSO, H 2 O N O O Br + Br OH N O O H + Note that the aryl ring does not react!!! For unsymmterical alkenes, halohydrin formation is Markovnikov-like in that the orientation of the addition of
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This note was uploaded on 03/11/2012 for the course CHEM 220A taught by Professor Sulikowski during the Fall '08 term at Vanderbilt.

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Ch7slides - Chapter 7: Alkenes: Reactions and Synthesis H C...

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