back

Chapter 6
Reactions of Alkynes

Lecture Resource (.ppt)

PowerPoint Image Gallery (.ppt)
06-00CO
Title
 2,2-Dichlorobutane
Caption
 Space-filling model of 2,2-dichlorobutane.
Notes
 2,2-Dichlorobutane is the product of the reaction of 1-butyne with two molecules of HCl.
Keywords
 2,2-dichlorobutane, space-filling, 1-butyne
06-00-04UN
Title
 1-Hexyne and 3-Hexyne
Caption
 Space-filling models of 1-hexyne and 3-hexyne.
Notes
 Giving the triple bond in an alkyne the lowest possible number takes priority over giving substituents attached to alkynes low numbers.
Keywords
 1-hexyne, 3-hexyne
06-00-09
Title
 Structure of Ethyne
Caption
 Chemical structure and ball-and-stick model of ethyne.
Notes
 Because each carbon in ethyne, also known as acetylene, is sp hybridized, the bond angles around these carbons are both 180 degrees.
Keywords
 structure, ethyne, ball-and-stick, acetylene
06-01a,b
Title
 Figure 6.1
Caption
 Orbital structures of ethyne.
Notes
 (a) Each of the two pi bonds of a triple bond is formed by side-to-side overlap of a p orbital of one carbon with a parallel p orbital of the adjacent carbon. (b) A triple bond consists of a sigma bond formed by end-on sp-sp overlap (yellow) and the two pi bonds shown in (a).
Keywords
 orbital, structures, ethyne, triple, bond, figure, 6.1
06-02
Title
 Figure 6.2
Caption
 Free-energy profiles for addition of electrophiles to alkenes and alkynes.
Notes
 Although alkynes are less stable than alkenes, they react more slowly with electrophiles. The activation energy for adding an electrophile to an alkyne is greater than that for an alkene.
Keywords
 free-energy, profiles, addition, electrophiles, alkene, alkyne, figure, 6.2
06-02-029UN
Title
 Borane and Disiamylborane
Caption
 Ball-and-stick models of borane and disiamylborane.
Notes
 Borane is favored for hydrating internal alkynes, because the alkyl groups attached to each carbon are sterically bulky enough to prevent the addition of a second B-H bond to the unsaturated reaction site. Disiamylborane is used to hydrate terminal alkynes, because the two secondary isoamyl groups attached to boron provide the steric bulk necessary to prevent the addition of the second B-H bond to the unsaturated reaction site.
Keywords
 ball-and-stick, borane, disiamylborane
06-02-035UN
Title
 Trans Alkenes from Alkynes
Caption
 Reductions of alkynes by metallic sodium or lithium dissolved in liquid ammonia yields trans alkenes.
Notes
 This reaction proceeds via the formation of a vinylic anion intermediate.
Keywords
 trans, alkenes, alkynes, vinylic, anion
06-02-037UN
Title
 Trans and Cis Vinylic Anions
Caption
 Equilibrium between trans and cis vinylic anions.
Notes
 Trans vinylic anions are more stable than cis vinylic anions. This leads to the predominance of trans products in reactions which generate vinylic anions, like metal–ammonia reductions of alkynes.
Keywords
 trans, cis, vinylic, anions, equilibrium
06-02-038UN
Title
 Carbon Electronegativities
Caption
 Electronegativities of carbon atoms decrease as the hybridization of these carbon atoms takes on more p character.
Notes
 Since sp-hybridized carbons are more electronegative than sp3-hybridized carbons, anions of sp-hybridized carbon atoms are more stable (weaker bases) than anions of sp3-hybridized carbon atoms. Therefore, sp-hybridized carbons attached to hydrogens (terminal alkynes) are stronger acids than sp3-hybridized carbons attached to hydrogens (alkanes).
Keywords
 carbon, electronegativities, hybridization
06-02-039UN
Title
 Eletronegativity vs. Acid Strength
Caption
 Atoms with the highest electronegativities yield the strongest acids when attached to hydrogen.
Notes
 Hydrogens attached to more electronegative sp-hybridized carbon atoms in alkynes are more acidic than hydrogens attached to less electronegative sp2-hybridized carbons in alkenes, which are in turn more acidic than hydrogens attached to even less electronegative sp3-hybridized carbons in alkanes.
Keywords
 electronegativity, acid, strength
06-02-041UN
Title
 Relative Acidities
Caption
 Electrostatic potential maps of various acids.
Notes
 Increasing amounts of blue color on hydrogen in the stronger acids indicate more positive charge on hydrogen due to increasing electronegativities of atoms attached to hydrogen.
Keywords
 relative, electrostatic, potential, maps, acidities, electronegativities
06-02-045PSS
Title
 Problem-Solving Strategy Part A
Caption
 Three nitrogen acids listed in order of decreasing acidity.
Notes
 The strongest acid has the nitrogen with the highest electronegativity (the sp-hybridized triple-bonded nitrogen).
Keywords
06-02-046PSS
Title
 Problem-Solving Strategy Part B
Caption
 Three nitrogen bases listed in order of decreasing basicity.
Notes
 The strongest base has the least electronegative (sp3-hybridized single-bonded) nitrogen.
Keywords

Title
 Table 6.1 Boiling Points of the Smallest Hydrocarbons
Caption
Notes
Keywords
© 1995-2002 by Prentice-Hall, Inc.
A Pearson Company
Distance Learning at Prentice Hall
Legal Notice