Alken reaction

Organic Chemistry
4th 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
I: early transition state
II: mid-transition state
III: later transition state
Reaction Rate and DG‡
more stable transition state
In a regioselective reaction, one constitutional isomer is the
major or the only product
Markovnikov’s Rule
The electrophile adds to the sp2 carbon that is bonded to the greater number of hydrogens

tert-Butyl cation is formed faster and it is more stable
Addition of Water to Alkene
Hydration of Propene
Acid-Catalyzed Addition of Alcohol
Rearrangement of Carbocation
1,2-hydride shift
a more stable
carbocation
a more stable
carbocation
Rearrangement of Carbocation


1,2-methyl shift
Carbocation does not always rearrange …
Carbocation Rearrangement


a more stable
carbocation
Ring Expansion
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
addition
Markovnikov
addition
(a pericyclic reaction)
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
Relative Stabilities of Alkyl Radicals
Calculating the Change in H°
Addition of Hydrogen to Alkenes
Catalytic Hydrogenation of an Alkene
Potential Energies of Pentene Isomers
Relative Stabilities of Alkenes
Steric Strain in Alkenes
Relative Stabilities of Dialkyl-Substituted Alkenes