AdE2-alkenes

AdE2-alkenes - Ad E 2 AND OTHER REACTIONS INVOLVING ALKENES...

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Unformatted text preview: Ad E 2 AND OTHER REACTIONS INVOLVING ALKENES Ad E 2 ADDITION REACTIONS--ALKENES General mechanism--the electrons in the alkene are the highest energy electrons in the molecule (i.e., they are in the HOMO). These electrons will attack an electrophile, leaving a positive charge (or a partial positive charge) on the most substituted carbon. Three variations are possible: one that involves a simple carbocation and one in which a halonium cation (bromonium cation) forms and dictates the stereochemical outcome of the reaction, and concerted reactions (hydroboration, epoxidation). Note that alkenes are weak nucleophiles and will only react with strong electrophiles. These electrophiles include H 3 O + , HCl, HBr, HI, H 2 SO 4 , Cl 2 , Br 2 , I 2 , carbocations, BH 3 , R 2 BH, and peracids. In reactions in which a positively charged intermediate is formed, the amount and nature of the nucleophiles present must be considered to understand and/or predict the outcomes of the reactions....
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This note was uploaded on 12/08/2009 for the course CHEM 351 taught by Professor Staff during the Spring '08 term at BYU.

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