CH 221 1st Edition Lecture 17Outline of Last Lecture I. EletrophilesII. NucleophilesIII. Two Step ReactionsIV. Thermodynamics and KineticsV. EquilibriumVI. Gibb’s Free Energy VII. Rates of ReactionOutline of Current Lecture VIII. Reaction Coordinate DiagramIX. EnzymesX. Addition of Hydrogen HalidesXI. Carbocation StabilityXII. RegioselectivityCurrent LectureVIII. Reaction coordinate diagram for each step of the addition of HBr to 2-Butene- The rate limiting step of the reaction is the step that has its transition state at the highest point of the reaction coordinate diagram - A catalyst provides a pathway for a reaction with a lower energy barrier- A catalyst does not change the energy of the starting point (the reactants) or the energy of the end point (the products)IX. Enzymes- Most biological reactions require a catalyst- Most biological catalysts are proteins called enzymes- Substrate + Enzymes = Product- The reactant of a biological reaction is a substrate- A substrate binds to an enzyme at its active siteX. Addition of Hydrogen Halides- Ex. 2,3-dimethyl-2-butene- Cyclohexene + HI = iodocyclohexeneThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Carbocation formation is the rate limiting step- 2-methylpropene + HCl = tert-butyl chloride- The tertiary carbocation is much more stable- Most stable tertiary> secondary> primary> methyl cation least stableXI. Carbocation Stability- Alkyl groups decrease the concentration of positive charge on the carbon- Hyperconjugation stabilizes a carbocation- The more stable carbocation is formed more rapidly- Electrophiles add to the sp2 carbon bonded to the most hydrogenXII. A regioselective reaction forms more of constitutional isomer, then , another- Completely regioselective- Highly regioselective- Moderately regioselective- First reaction is more highly regioselective- Some reactions not regioselective at all- Alkene + water (in the presence of H2SO4) =
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