D.M. Collard 2007TOPIC 8. ADDITIONS TO ALKENES AND ALKYNES (Chapter 8 and parts of chapters 7, 10 and 11)LOBJECTIVES1. Describe mechanisms for addition reactions of alkenes and alkynes2. Predict the structure of the product(s) of addition reactions3. Understand the mechanisms which explain the regiochemical and stereochemical outcome of addition reactions4. Use combination of substitution, elimination and addition chemistry to propose synthetic routes to useful value-added compoundsD.M. Collard 2007ADDITION REACTIONSAddition of H2-H2/Pd (alkene, alkyne)-H2/Lindlar catalyst (alkyne → cis alkene)- dissolving metal reduction (alkyne → trans alkene)Addition of H-Hal- Markovnikov-anti-MarkovnikovAddition of H2O-H3O+(regiochemistry)- Oxymercuration-demercuration (regiochemistry, stereochemistry)- Hydroboration-oxidation (regiochemistry, stereochemistry)- hydration of alkynes (regiochemistry)Addition of Hal2-Hal2(regiochemistry, stereochemistry)-Hal2/H2O (regiochemistry)Generation and reaction of carbenesEpoxidationNucleopihilic ring opening reactions of epoxides (H2O, ROH, HCN, RMgHal)syn-HydroxylationOxidative cleavage of alkenes and alkynes-KMnO4- OzonolysisRadical Polymerization~MAKE FLASHCARDS AFTER EACH LECTURE~Lecture 1Lecture 2Lecture 3Lecture 4Lecture 5HYDROGENATION OF ALKENESAND ALKYNESHydrogenation of AlkenesCH3CH3H2Pd or PtProb:7.40-42;8.30e,g,i,37,45S:7.12-7.14D.M. Collard 2007Hydrogenation of AlkynesComplete Hydrogenationcis-SemihydrogenationCCH2Pt or PdCCH2Pd/CaCO3NCC2Li, 2CH3OH NH3 (solvent)CCLiLiLiDissolving Metal ReductionD.M. Collard 2007PREVIEW OF REACTIVITYAlkenes and Alkynes are Weakly _____ and Weakly _____________CCECC EHBrS:8.1ADDITION OF HYDROGEN HALIDESTO ALKENES AND ALKYNESOverviewCCHCCBrBrHCH3CH3ICCCCClHHProb:8.27,28a,b,f,j,29b-g,35S:8.2-8.3;18.19;10.9D.M. Collard 2007Addition of H-Hal to AlkenesMechanismCCHBrRegiochemistryMarkovnikov’s RuleIn the addition of HX to an unsymmetrical alkene, the hydrogen adds to the_____________ substituted carbon and the X groups adds to the _____________ substituted carbon.CCH2H3CH3CHBrD.M. Collard 2007The Basis of Markovnikov’s Rule: Stability of CarbocationsCCHHHCCH2H3CH3CHBrMechanistic Restatement of Markovnikov’s RuleIn the ionic addition of HX to an unsymmetrical alkene, protonation gives the more stable carbocation as an intermediate.The more substituted carbocation is formed. Remember hyperconjugation!Stereochemistry of H–Hal Addition to AlkenesBrHBrBrCHD.M. Collard 2007Anti-Markovnikov Addition of H-Hal to AlkenesMechanistic Rationale for Anti-Markovnikov AdditionCCH2HH3CHBrAddition of H-Hal to AlkynesRCCHRCCR'HClCCl4D.M. Collard 2007~ MAKE FLASHCARDS ~HydrogenationDissolving metal reductionHydrogenation over Lindlar catalystMarkovnikov addition of H-HalAnti-Markovnikov addition of H-Hal…..more next lectureADDITION REACTIONSAddition of H2-H2/Pd (alkene, alkyne)-H2/Lindlar catalyst (alkyne → cis alkene)- dissolving metal reduction (alkyne → trans alkene)Addition of H-Hal-Markovnikov- anti-MarkovnikovAddition of H2O-H3O+(regiochemistry)- Oxymercuration-demercuration (regiochemistry, stereochemistry)- Hydroboration-oxidation (regiochemistry, stereochemistry)- hydration of alkynes (regiochemistry)Addition of Hal2-Hal2(regiochemistry, stereochemistry)-Hal2/H2O (regiochemistry)Generation and reaction of carbenesEpoxidationNucleopihilic ring opening reactions of epoxides (H2O, ROH, HCN, RMgHal)syn-HydroxylationOxidative cleavage of alkenes and alkynes-KMnO4- OzonolysisRadical Polymerization~MAKE FLASHCARDS AFTER EACH LECTURE~Lecture 1Lecture 2Lecture 3Lecture 4Lecture 5D.M. Collard 2007Addition of Water to AlkenesCCHOH2H2OH2SO4SYNTHESIS OF ALCOHOLSBY HYDRATION OF ALKENESLProb:8.27c,32,5811.33,35(a-g),38(a,d),39,46,48S:8.4-8.11Proceeds via Markovnikov additionD.M. Collard 2007Rearrangements During Acid Catalyzed Hydration of AlkenesIntermediate carbocations can rearrange.H2SO4H2OCH3OHCH3HCH3OHHnot:Oxymercuration-Demercuration of Alkenese.g.,Step 1: OxymercurationStep 2: DemercurationCC(CH3CO2)2HgH2OHO Hg OCH3ONaBH4NaOHHO Hg OCH3OHO H1. (CH3CO2)2Hg H2O2. NaBH4, NaOHOHD.M. Collard 2007MechanismOHgOOOOHgOH2OHydroboration-Oxidation: Anti-MarkovnikovHydration of Alkenese.g., Step 1: HydroborationStep 2: OxidationCCB2H6HBH2H2O2NaOHHBH2HOHCH3CH3HOH1. B2H62. H2O2 NaOHD.M. Collard 2007Mechanism: RegiochemistryBHHBH2O2NaOH, H2OB2H6BH3StereochemistryCH3CH3HBCH3HOHD.M. Collard 2007RCC HRCCHH2OHg++, H2SO4HHOHydration of Alkynes (covered in 16.5B)SYNTHETIC STRATEGIESProb:7.24CNProblem: Synthesize cis-1-cyano-2-methylcyclohexane (shown below) using any hydrocarbon.D.M. Collard 2007Problem: Female houseflies attract males with a pheromone which has been shown to be Z-9-tricosene (C23H46). Synthesize this compound starting with organic compounds containing 13 or less carbon atoms.H Hn-C8H17n-C13H27ADDITION REACTIONSAddition of H2-H2/Pd (alkene, alkyne)-H2/Lindlar catalyst (alkyne → cis alkene)- dissolving metal reduction (alkyne → trans alkene)Addition of H-Hal-Markovnikov- anti-MarkovnikovAddition of H2O-H3O+(regiochemistry)- Oxymercuration-demercuration (regiochemistry, stereochemistry)- Hydroboration-oxidation (regiochemistry, stereochemistry)- hydration of alkynes (regiochemistry)Addition of Hal2-Hal2(regiochemistry, stereochemistry)-Hal2/H2O (regiochemistry)Generation and reaction of carbenesEpoxidationNucleopihilic ring opening reactions of epoxides (H2O, ROH, HCN, RMgHal)syn-HydroxylationOxidative cleavage of alkenes and alkynes-KMnO4- OzonolysisRadical Polymerization~MAKE FLASHCARDS AFTER EACH LECTURE~Lecture 1Lecture 2Lecture 3Lecture 4Lecture 5D.M. Collard 2007ADDITION OF BROMINE AND CHLORINETO ALKENES AND ALKYNESOverviewCCCl ClBrBrBrBr50% S,S trans50% R,R trans+HCCl3CCl4CCCl ClClClCCl4Cl2Br22 Cl2LProb:8.30(c,d),31,54S:8.12-8.14;8.18Addition of Hal2to AlkenesStereochemistryCH3H3CHHHH3CCH3HH3CHBrBrCH3HBrBrCH3H3CHHBrBrHH3CCH3HBr2Br2H3CHBrBrHCH3D.M. Collard 2007MechanismCH3H3CHHBr BrFormation of HalohydrinsCCCl OHCl2H2OCH3CH3OHBrBr2H2OD.M. Collard 2007MechanismHCH3HHCl2H2OCl ClAddition of Hal2to AlkynesRCCHRCCR'Br2HCCl3D.M. Collard 2007ADDITION REACTIONSAddition of H2-H2/Pd (alkene, alkyne)-H2/Lindlar catalyst (alkyne → cis alkene)- dissolving metal reduction (alkyne → trans alkene)Addition of H-Hal-Markovnikov- anti-MarkovnikovAddition of H2O-H3O+(regiochemistry)- Oxymercuration-demercuration (regiochemistry, stereochemistry)- Hydroboration-oxidation (regiochemistry, stereochemistry)-