4.4 bonding in alcohols and alkyl halides
DESCRIPTION
4.4 Bonding in Alcohols and Alkyl Halides. H. H. H. H. O. C. Cl. C. Dipole Moments. alcohols and alkyl halides are polar. d +. H. d +. d +. d –. d –. H. H. m = 1.9 D. m = 1.7 D. Dipole Moments. alcohols and alkyl halides are polar. m = 1.9 D. m = 1.7 D. - PowerPoint PPT PresentationTRANSCRIPT
4.44.4Bonding in AlcoholsBonding in Alcohols
and Alkyl Halidesand Alkyl Halides
HH
HH
HH
alcohols and alkyl halides are polaralcohols and alkyl halides are polar
= 1.7 D= 1.7 D = 1.9 D= 1.9 D
HH
HH
CC OO
HH
HH
CC ClCl++
–– ––++
++
Dipole MomentsDipole Moments
alcohols and alkyl halides are polaralcohols and alkyl halides are polar
= 1.7 D= 1.7 D = 1.9 D= 1.9 D
Dipole MomentsDipole Moments
+ + – –
– – + +
+ + – – + + – – + + – –
Dipole-Dipole Attractive ForcesDipole-Dipole Attractive Forces
+ + – –
– – + +
+ + – – + + – – + + – –
Dipole-Dipole Attractive ForcesDipole-Dipole Attractive Forces
Boiling pointBoiling pointSolubility in waterSolubility in water
DensityDensity
4.54.5Physical Properties of Physical Properties of
Alcohols and Alkyl Halides:Alcohols and Alkyl Halides:Intermolecular ForcesIntermolecular Forces
4444 4848 4646
-42-42 -32-32 +78+78
00 1.91.9 1.71.7
CHCH33CHCH22CHCH33 CHCH33CHCH22FF CHCH33CHCH22OHOH
MolecularMolecularweightweight
BoilingBoilingpoint, °Cpoint, °C
DipoleDipolemoment, Dmoment, D
Effect of Structure on Boiling PointEffect of Structure on Boiling Point
4444
--4242
00
CHCH33CHCH22CHCH33
MolecularMolecularweightweight
BoilingBoilingpoint, °Cpoint, °C
DipoleDipolemoment, Dmoment, D
Intermolecular forcesIntermolecular forcesare weak.are weak.
Only intermolecularOnly intermolecularforces are inducedforces are induceddipole-induced dipoledipole-induced dipoleattractions.attractions.
Effect of Structure on Boiling PointEffect of Structure on Boiling Point
4848
-32-32
1.91.9
CHCH33CHCH22FF
MolecularMolecularweightweight
BoilingBoilingpoint, °Cpoint, °C
DipoleDipolemoment, Dmoment, D
A polar molecule;A polar molecule;therefore dipole-dipoletherefore dipole-dipoleand dipole-inducedand dipole-induceddipole forces contributedipole forces contributeto intermolecular to intermolecular attractions.attractions.
Effect of Structure on Boiling PointEffect of Structure on Boiling Point
4646
+78+78
1.71.7
CHCH33CHCH22OHOH
MolecularMolecularweightweight
BoilingBoilingpoint, °Cpoint, °C
DipoleDipolemoment, Dmoment, D
Highest boiling point;Highest boiling point;strongest intermolecularstrongest intermolecularattractive forces.attractive forces.
Hydrogen bonding isHydrogen bonding isstronger than otherstronger than otherdipole-dipole attractions.dipole-dipole attractions.
Effect of Structure on Boiling PointEffect of Structure on Boiling Point
++––
––++
Figure 4.4 Hydrogen bonding in ethanolFigure 4.4 Hydrogen bonding in ethanol
Figure 4.4 Hydrogen bonding in ethanolFigure 4.4 Hydrogen bonding in ethanol
Boiling point increases with increasingBoiling point increases with increasingnumber of halogensnumber of halogens
CHCH33Cl Cl -24°C-24°C
CHCH22ClCl22 40°C40°C
CHClCHCl33 61°C61°C
CClCCl44 77°C77°C
CompoundCompound Boiling PointBoiling Point
Even though CClEven though CCl4 4 is the only compound in this list without is the only compound in this list without a dipole moment, it has the highest boiling point.a dipole moment, it has the highest boiling point.
Induced dipole-induced dipole forces are greatest in CClInduced dipole-induced dipole forces are greatest in CCl44 because it has the greatest number of Cl atoms. Cl is more because it has the greatest number of Cl atoms. Cl is more polarizable than H. polarizable than H.
But trend is not followed when halogenBut trend is not followed when halogenis fluorineis fluorine
CHCH33CHCH22FF -32°C-32°C
CHCH33CHCHFF22 -25°C-25°C
CHCH33CCFF33 -47°C-47°C
CCFF33CCFF33 -78°C-78°C
CompoundCompound Boiling PointBoiling Point
But trend is not followed when halogenBut trend is not followed when halogenis fluorineis fluorine
CHCH33CHCH22FF -32°C-32°C
CHCH33CHCHFF22 -25°C-25°C
CHCH33CCFF33 -47°C-47°C
CCFF33CCFF33 -78°C-78°C
CompoundCompound Boiling PointBoiling Point
Fluorine is not very polarizable and induced dipole-Fluorine is not very polarizable and induced dipole-induced dipole forces decrease with increasing induced dipole forces decrease with increasing fluorine substitution.fluorine substitution.
Solubility in waterSolubility in water
Alkyl halides are insoluble in water.Alkyl halides are insoluble in water.
Methanol, ethanol, isopropyl alcohol areMethanol, ethanol, isopropyl alcohol arecompletely miscible with water.completely miscible with water.
The solubility of an alcohol in waterThe solubility of an alcohol in waterdecreases with increasing number of decreases with increasing number of carbons (compound becomescarbons (compound becomesmore hydrocarbon-like).more hydrocarbon-like).
++––
––
++
––++
Figure 4.5 Hydrogen Bonding Figure 4.5 Hydrogen Bonding Between Ethanol and WaterBetween Ethanol and Water
DensityDensity
Alkyl fluorides and alkyl chlorides Alkyl fluorides and alkyl chlorides areareless dense than water.less dense than water.
Alkyl bromides and alkyl iodides are Alkyl bromides and alkyl iodides are more dense than water.more dense than water.
All liquid alcohols have densities of All liquid alcohols have densities of about 0.8 g/mL.about 0.8 g/mL.