Anken

Organic Chemistry
4th Edition
Paula Yurkanis Bruice
Chapter 3

Alkenes:

Structures, Nomenclature, and
an Introduction to Reactivity

Thermodynamics
and Kinetics
Irene Lee
Case Western Reserve University
Cleveland, OH
©2004, Prentice Hall

Hydrocarbons containing double bonds
Alkenes
Noncyclic alkene:
CnH2n


Cyclic alkene:
CnH2n–2
Molecular Formula of Alkene
Systematic Nomenclature of Alkenes

Name with the lowest functional group number and
then the lowest substituent numbers
No numbering of the functional group is needed in
a cyclic alkene
Special Nomenclatures
Structure of Alkene
Isomers of Alkene
Dipole Moments of Alkene Isomers
Conversion of alkene isomers requires breaking of
the p bond between the two sp2 carbons
Cis-Trans Interconversion in Vision
Naming by the E,Z System
Rule 1: Consider the atomic number of the
atoms bonded directly to a specific sp2
carbon.
Rule 2: If there is a tie, consider the atoms attached to the tie.
Rule 3: Multiple bonds are treated as attachment
of multiple single bonds.
Rule 4: Rank the priorities by mass number in
isotopes.
An alkene is an electron-rich molecule
Nucleophile: an electron-rich atom or molecule
that shares electrons with electrophiles
A nucleophile
Nucleophiles are attracted to electron-deficient
atoms or molecules (electrophiles)
Electrophilic Addition of HBr to Alkene
Curved Arrows in Reaction Mechanisms
Utilization of Curved Arrows
Rules for Use of Curved Arrows
A Reaction Coordinate Diagram
Transition states have partially formed bonds
Intermediates have fully formed bonds
Thermodynamics describes the properties of a
system at equilibrium
Thermodynamic Parameters
DG° = DH° – TDS°
If DS° is small compared to DH°, DG° ~ DH°
Exergonic Reaction
–DG°
Endergonic Reaction
+DG°
DH° can be calculated from bond dissociation
energies
Solvation: the interaction between a solvent
and a molecule (or ion) in solution
Solvation can affect DH° and/or DS°, which ultimately affects DG°
Kinetics deals with the rate of chemical reactions
and the factors that affect those rates
The rate-limiting step controls the overall rate of the reaction
The free energy between the transition state
and the reactants
DG‡:
(free energy of transition state) – (free energy of reactants)
DG‡ = DH‡ – TDS‡
DH‡:
(enthalpy of transition state) – (enthalpy of reactants)
DS‡:
(entropy of transition state) – (entropy of reactants)
Rates and Rate Constants
The Arrhenius Equation
Rate Constants and the Equilibrium
Constant
Keq = k1/k–1 = [B]/[A]
Transition State versus Intermediate
Transition states have partially formed bonds
Intermediates have fully formed bonds
intermediate
intermediate
Electrophilic Addition of HBr to 2-Butene
The rate-limiting step controls the overall rate of the
reaction