Lecture 3 - Alkene & Alkyl Halide Review - Jau~ c:ll.>...

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Ja/\u~~ c:ll.¥> Review from 1st Vear Organic Chemistry: Synthesis & Reactions of Alkenes Discussed briefly in class: Chapter 8 (except 8.9- 8.11) Material that should be reviewed independently: ~hapter 7
Chemistry Connections Terpenes in Natural Product Synthesis • Terpenes represent the largest class of secondary metabolites that are made up of linked isoprene units, leading to an extensive array of complex molecular structures with a broad range of biological properties. . 1soprene N eotri pte rif ord in 0 H ~# I potent inhibitor of HIV replication in H9 human lymphocyte cells 2 (.Ol'l\'l\01\ ttc-.ft\I\ ~ ('l~~I Terpenes as Anti-HIV Drugs n HIV is a global epidemic with over 35 million people carrying the virus world-wide! New anti-retrovirals wit h better efficacy and safety are needed
Reaction of Alkenes: HX Addition Markovnikov's Rule: In electrophilic addition reactions of alkenes, the electrophile adds to the least substituted carbon giving rise to the more stable intermediate. ~ 10..ie.c e..re.<~~ 1Me.<tt\et;1fat<.. Example: Addition of HX Compare to: -1r Et20 (solvent) H-Br Et20 (solvent) f'; bof"\d l:)ttCliC.S v.\V."'-1"'°1 1 NST rt~M°'-~O~ H ""I.I< "llit o.6 n 8Br Br H Markovnikov Addition (only product) Non-Markovnikov Addition {NOT observed} Regio~ele.c.tivity: When two or more regioisomers (constitutional isomers) are possible but one is preferentially formed 3 /
Reaction of Alkenes: Halogenation with X2 Chlorine (Cl2) and bromine (Br2) react with alkenes to give dihalide products through an anti-addition mechanism: . ' eieerroen111 c. a.O~ffi on flt Br-Br H H bromonium ion ~loc:lll.l.ff\ i 1)(\ e -i.--Br n...s-n ~ flom o(!''tte--fcr-L~ Stereoselectivity: The preferential formation of one stereoisomer over another. Example: anti-addition vs syn-addition p.':::.

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