Figure Number: 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.

Figure Number: 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.

Figure Number: 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.

Figure Number: 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).

Figure Number: 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.

Figure Number: 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.

Figure Number: 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.

Figure Number: 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.

Figure Number: 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).

Figure Number: 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.

Figure Number: 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.

Figure Number: 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).

Figure Number: 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.

Figure Number: Title: Table 6.1  Boiling Points of the Smallest Hydrocarbons Caption: Notes: