Organic Chemistry 4 th Edition Paula Yurkanis Bruice Chapter 4 Reactions of Alkenes Irene Lee Case Western Reserve University Cleveland, OH ©2004, Prentice Hall Electrophilic Addition of Alkenes Addition of Hydrogen Halides What is the product? a more stable carbocation Carbocation formation is the rate-limiting step Carbocation Stabilities Alkyl groups decrease the concentration of positive charge in the carbocation Delocalization of Electrons Molecular Orbital Diagram in a Hyperconjugation System Hammond postulate: the transition state will be more similar to the species that it is closer to energetically Exergonic reaction: early transition state Endergonic reaction: late transition state [...]... later transition state Reaction Rate and ∆G‡ more stable transition state lower ∆G‡ faster reaction rate Markovnikov’s Rule The electrophile adds to the sp2 carbon that is bonded to the greater number of hydrogens In a regioselective reaction, one constitutional isomer is the major or the only product tert-Butyl cation is formed faster and it is more stable Addition of Water to Alkene Hydration of Propene... Expansion a more stable carbocation Addition of Halogens to Alkene Addition of Halogens in the Presence of Water Consider the transition states … Oxymercuration and Mercuration of Alkene Demercuration by Reduction Addition of Borane Hydroboration–Oxidation Anti-Markovnikov’s rule in product formation Anti-Markovnikov addition (a pericyclic reaction) Markovnikov addition Formation of Alkyl Boranes OH... Anti-Markovnikov addition (a pericyclic reaction) Markovnikov addition Formation of Alkyl Boranes OH Replacement of Boron Anti-Markovnikov Addition of an OH Group Reaction of Carbene with Alkene Synthesis of Bromobutane Generation of Radicals Addition of Radicals to Alkene . Bruice Chapter 4 Reactions of Alkenes Irene Lee Case Western Reserve University Cleveland, OH ©2004, Prentice Hall Electrophilic Addition of Alkenes Addition. later transition state Reaction Rate and ∆G ‡ more stable transition state lower ∆G ‡ faster reaction rate In a regioselective reaction, one constitutional