TAILIEUCHUNG - Ebook Arrow pushing in organic chemistry: Part 2

(BQ) Part 2 book "Arrow pushing in organic chemistry" has contents: Elimination reactions, addition reactions (addition of halogens to double bonds, additions to carbonyls, summary), moving forward (functional group manipulations, name reactions, reagents, final comments) | Chapter 6 Elimination Reactions Until now, discussions have focused only on how carbanions and carbocations behave under conditions favorable for nucleophilic substitutions. However, these species may undergo other types of reactions in which unsaturation is introduced into the molecule. Such reactions are called elimination reactions and should be considered whenever charged species are of importance to the mechanistic progression of a molecular transformation. In previous chapters, SN1 and SN2 reactions were discussed. In this chapter, the corresponding E1 and E2 elimination mechanisms are presented. E1 ELIMINATIONS Having addressed the chemistry of carbocations and associated SN1 reaction mechanisms, it is appropriate to begin discussions of elimination reactions with the related E1 mechanism. As addressed in Chapter 5, carbocations generated from solvolysis reactions can undergo various types of rearrangements that include hydride and alkyl shifts. Furthermore, these shifts were rationalized when the empty p orbital associated with the positive charge is aligned in the same plane with the migrating group. Figure reiterates the process of hyperconjugation necessary for these shifts to occur. Furthermore, Figure reiterates that hyperconjugation can be viewed as introducing double-bond character to a carbocation. Carrying this rationale one step further, if the double-bond character in a given carbocation becomes stabilized through full dissociation of a proton, the result, illustrated in Scheme , is formation of a full double bond through an E1 elimination mechanism. Arrow Pushing in Organic Chemistry: An Easy Approach to Understanding Reaction Mechanisms. By Daniel E. Levy Copyright # 2008 John Wiley & Sons, Inc. 101 102 ELIMINATION REACTIONS Figure Hyperconjugation occurs when a carbon– hydrogen bond lies in the same plane as a carbocation’s vacant p orbital. Figure Hyperconjugation can be viewed as formation of a .

• Toán học
• Arrow pushing in organic chemistry
• Organic chemistry
• Elimination reactions
• Addition reactions
• Moving forward
• Final comments
• Bases and nucleophiles
• S(N)2 substitution reactions
• S(N)1 substitution reactions