3 Addition Reactions: HX to Alkenes General Order of HX Reactivity:HI > HBr > HCl > HFUsually Dissolved in Solvent (CH3CO2H, CH2Cl2)
4 Addition Reactions: HBr to Alkenes p Bond (Nucleophile) Protonate Carbocation IntermediateCarbocation Captured by Br¯ (Nucleophile) HBr AddedHBr (or other HX) Addition in Two Overall StepsH+ and Carbocation are the Respective ElectrophilesThis is a SYMMETRIC Alkene ASYMMETRIC ALKENES?
5 Markovnikov’s Rule: HBr to Alkenes 2-Bromopropane is Major ProductOnly Very Small Amount of 1-Bromopropane ObservedTrue With Other Alkenes
6 Markovnikov’s Rule: Why? Product Distribution Explained When Looking at IntermediatesConsider Carbocation Stability (2° > 1°)Major Product Formed From More Stable C+ Intermediate
7 Markovnikov’s Rule: C+ Stability We Know 2° Carbocations More Stable Than 1°Major Product Formed From More Stable C+ IntermediateMeans TS in 2° Carbocation Pathway Lower in EnergyLower Energy of ActivationActivation Energies in 1° Carbocation Pathways Much Larger
9 Alcohols From Alkyl Hydrogen Sulfates HYDROLYSIS Reaction of Alkyl Hydrogen SulfateSimply Heat the Sulfate in WaterNet Reaction is Markovnikov Addition of H2O to AlkeneUsed in One Industrial Ethanol Making Process
10 Addition of H2O to Alkenes: Hydration HYDRATION Reaction of an Alkene