back

Chapter 11
Elimination Reactions of Alkyl Halides

Lecture Resource (.ppt)

PowerPoint Image Gallery (.ppt)

 
11-00CO
Title
 Elimination Reaction
Caption
 Electrostatic potential maps and structures of reactants and products of the elimination reaction undergone by methoxide and 3-chloropentane.
Notes
 Elimination reactions occur when nucleophiles act as bases rather than nucleophiles. The nucleophile removes a proton on the carbon adjacent to the carbon containing the leaving group. The sigma bond between this adjacent carbon and the hydrogen becomes a pi bond between the adjacent carbon and the carbon bearing the leaving group, and the leaving group leaves. These steps, done in different orders in different circumstances, yield alkene products.
Keywords
 electrostatic, potential, maps, methoxide, chloropentane, elimination
11-00-04.1UN
Title
 E2 Reactivities
Caption
 Relative reactivities of alkyl halides in E2 reactions.
Notes
 Alkyl halides with better leaving groups react faster by E2 than do alkyl halides with poor (unstable) leaving groups.
Keywords
 E2, reactivities, alkyl, halide, leaving, groups
11-01
Title
 Figure 11.1
Caption
 Reaction coordinate diagram for the E2 reaction of 2-bromobutane and methoxide ion.
Notes
 Since the transition state is somewhat product-like, formation of the more stable internal alkene product involves a more stable transition state, less activation energy, and a faster relative rate.
Keywords
 figure, 11.1, reaction coordinate, diagram, E2, 2-bromobutane, methoxide
11-01-05.1UN
Title
 Products of E2 Reactions
Caption
 Products of the reactions of hydroxide ion with 4-chloro-5-methyl-1-hexene and 2-bromo-3-methyl-1-phenylbutane.
Notes
 E2 reactions usually yield predominantly the most stable alkene products, which in this case is the conjugated alkene products.
Keywords
 products, E2, conjugated, alkene
11-01-07T01
Title
 Table 11.1 Effect of steric properties on distribution of products in an E2 reaction
Caption
Notes
Keywords
11-01-09T02
Title
 Table 11.2 More substituted product/ Less substituted product
Caption
 Products obtained from the E2 reaction of methoxide and 2-halohexanes.
Notes
 The reaction with fluoride leaving group yields the less stable terminal alkene product predominantly. With fluoride as the leaving group, the transition state resembles the carbanion obtained by removing hydrogen from a carbon adjacent to the carbon bearing the leaving group more than it (the transition state) resembles the product alkene. Since a primary (terminal) carbanion is more stable than a secondary (internal) carbanion, this reaction yields mostly terminal olefin. The hydrogen is abstracted from the terminal carbon in preference to the internal carbon.
Keywords
 table, 11.2, E2, methoxide, 2-halohexanes
11-01-25.1UN
Title
 Hyperconjugation
Caption
 Orbital picture of a carbocation stabilized by hyperconjugation.
Notes
 Hyperconjugation makes a hydrogen attached to a carbon adjacent to a carbocation more acidic.
Keywords
 hyperconjugation, orbital, carbocation, acidic, hydrogen
11-02
Title
 Figure 11.2
Caption
 Reaction coordinate diagram for the E1 reaction of 2-chloro-2-methylbutane with base.
Notes
 The major product is the more stable alkene, because both products come from a common intermediate and the relative stabilities of the transition states leading to products from the common intermediate determine which product forms faster, even though these transition states occur after the rate-determining step. The second transition state in the reaction path has a small amount of product character, so the transition state leading to the more stable product is slightly more stable.
Keywords
 figure, 11.2, reaction coordinate, diagram, E1, 2-chloro-2-methylbutane
11-02-01UN
Title
 Alkyl Effect on E1 Reactivities
Caption
 Relative reactivities of alkyl halides in an E1 reaction.
Notes
 Relative reactivities of alkyl halides in E1 reactions parallels the stabilities of the corresponding alkyl cations.
Keywords
 E1, reactivity, alkyl, halides, cations, stabilities
11-02-01.1UN
Title
 Leaving Group Effect on E1 Reactivities
Caption
 Relative reactivities of alkyl halides in an E1 reaction.
Notes
 Relative reactivities parallel leaving-group (halide) stability.
Keywords
 leaving, group, E1, reactivities, alkyl, halide
11-03
Title
 Figure 11.3
Caption
 Reaction coordinate diagram for the E2 reaction of 2-bromopentane with ethoxide ion.
Notes
 The more stable E alkene has the more stable transition state, so it is formed more rapidly than the Z alkene.
Keywords
 figure, 11.3, reaction coordinate, diagram, E2, 2-bromopentane
11-03-00UN
Title
 (E)- and (Z)-2-pentene
Caption
 Electrostatic potential maps and structures of (E)-2-pentene and (Z)-2-pentene.
Notes
 (Z)-2-Pentene is less stable because of steric repulsions between hydrogens attached to the methyl and ethyl groups situated on the same side of the double bond, as can be seen from the potential maps.
Keywords
 (E)-2-pentene, (Z)-2-pentene, electrostatic, potential, maps
11-03-30UN
Title
 Deuterium Kinetic Isotope Effect
Caption
 Definition of deuterium kinetic isotope effect.
Notes
 Deuterium kinetic isotope effects greater than 1.0 indicate that the bond attaching H or D to the molecule under study is being broken in the rate-determining step.
Keywords
 deuterium, kinetic, isotope, effect

Title
 Table 11.3 Summary of the Reactivity of Alkyl Halides in Elimination Reactions
Caption
Notes
Keywords

Title
 Table 11.4 Stereochemistry of Substitution and Elimination Reactions
Caption
Notes
Keywords

Title
 Table 11.5 Relative Reactivities of Alkyl Halides
Caption
Notes
Keywords

Title
 Table 11.6 Summary of the Products Expected in Substitution and Elimination Reactions
Caption
Notes
Keywords
11-01-07T01
Title
 Table 11.1 Effect of steric properties on distribution of products in an E2 reaction
Caption
Notes
Keywords
11-01-09T02
Title
 Table 11.2 More substituted product/ Less substituted product
Caption
 Products obtained from the E2 reaction of methoxide and 2-halohexanes.
Notes
 The reaction with fluoride leaving group yields the less stable terminal alkene product predominantly. With fluoride as the leaving group, the transition state resembles the carbanion obtained by removing hydrogen from a carbon adjacent to the carbon bearing the leaving group more than it (the transition state) resembles the product alkene. Since a primary (terminal) carbanion is more stable than a secondary (internal) carbanion, this reaction yields mostly terminal olefin. The hydrogen is abstracted from the terminal carbon in preference to the internal carbon.
Keywords
 table, 11.2, E2, methoxide, 2-halohexanes
© 1995-2002 by Prentice-Hall, Inc.
A Pearson Company
Distance Learning at Prentice Hall
Legal Notice