Transcript IMF and Molecular Properties

IMF and Molecular Properties
Jan 12, 2012
Intermolecular Forces and Physical
Properties
• Virtual ChemBook, Elmhurst College
Solvents and Boiling Points
Ether (diethyl ether)
Dichloromethane
(methylene chloride)
acetone
methanol
Tetrahydrofuran
(THF)
35 oC
40 oC
56 oC
65 oC
66 oC
hexanes
Ethyl acetate
(EtOAC)
ethanol
acetonitrile
water
69 oC
77 oC
78 oC
82 oC
100 oC
toluene
Pyridine (pyr)
Acetic acid
Dimethyl formamide
(DMF)
Dimethylsulfoxide
(DMSO)
111 oC
115 oC
118 oC
153 oC
189 oC
Boiling Point Trend: Mass
Ether (diethyl ether)
Dichloromethane
(methylene chloride)
acetone
methanol
Tetrahydrofuran
(THF)
35 oC
40 oC
56 oC
65 oC
66 oC
74 amu
85 amu 58 amu
65 amu
32 amu
72 amu
hexanes
Ethyl acetate
(EtOAC)
ethanol
acetonitrile
water
69 oC
77 oC
78 oC
82 oC
100 oC
86 amu
88 amu
46 amu
41 amu
18 amu
toluene
Pyridine (pyr)
Acetic acid
Dimethyl formamide
(DMF)
Dimethylsulfoxide
(DMSO)
111 oC
115 oC
118 oC
153 oC
189 oC
92 amu
79 amu
60 amu
73 amu
78 amu
Intermolecular Forces
• Hydrogen bonding
– Acceptor/donor
• Dipole/dipole
• Dipole/induced dipole
• Induced dipole/induced dipole
– Also called London dispersion forces
VDWs Forces
H-Bond Donor, Acceptor, Neither, or Both
Ether (diethyl ether)
Dichloromethane
(methylene chloride)
acetone
methanol
Tetrahydrofuran
(THF)
35 oC
40 oC
56 oC
65 oC
66 oC
hexanes
Ethyl acetate
(EtOAC)
ethanol
acetonitrile
water
69 oC
77 oC
78 oC
82 oC
100 oC
toluene
Pyridine (pyr)
Acetic acid
Dimethyl formamide
(DMF)
Dimethylsulfoxide
(DMSO)
111 oC
115 oC
118 oC
153 oC
189 oC
Polar Protic, Polar Aprotic, Nonpolar
Ether (diethyl ether)
Dichloromethane
(methylene chloride)
acetone
methanol
Tetrahydrofuran
(THF)
35 oC
40 oC
56 oC
65 oC
66 oC
hexanes
Ethyl acetate
(EtOAC)
ethanol
acetonitrile
water
69 oC
77 oC
78 oC
82 oC
100 oC
toluene
Pyridine (pyr)
Acetic acid
Dimethyl formamide
(DMF)
Dimethylsulfoxide
(DMSO)
111 oC
115 oC
118 oC
153 oC
189 oC
London Forces in Nonpolar Solvents
Ether (diethyl ether)
Dichloromethane
(methylene chloride)
acetone
methanol
Tetrahydrofuran
(THF)
35 oC
40 oC
56 oC
65 oC
66 oC
hexanes
Ethyl acetate
(EtOAC)
ethanol
acetonitrile
water
69 oC
77 oC
78 oC
82 oC
100 oC
toluene
Pyridine (pyr)
Acetic acid
Dimethyl formamide
(DMF)
Dimethylsulfoxide
(DMSO)
111 oC
115 oC
118 oC
153 oC
189 oC
General Principles
• If molecules are about the same mass
– H-bonding > Dipole-dipole > Induced dipole
• Induced dipole is weakest interaction, but as
surface area increases, cumulative effect can
overcome stronger IMF
• Strategy for predicting relative boiling points
Solubility
• “Like dissolves
like”
• Based on IMF
Miscibility and Density
• Miscibility spectrum
• Density
– Organics (0.7 g/mL)
– Aqueous (1.0
g/mL)
– Halogenated (1.3
g.mL)
Miscibility with Water
Ether (diethyl ether)
Dichloromethane
(methylene chloride)
acetone
methanol
Tetrahydrofuran
(THF)
35 oC
40 oC
56 oC
65 oC
66 oC
hexanes
Ethyl acetate
(EtOAC)
ethanol
acetonitrile
water
69 oC
77 oC
78 oC
82 oC
100 oC
toluene
Pyridine (pyr)
Acetic acid
Dimethyl formamide
(DMF)
Dimethylsulfoxide
(DMSO)
111 oC
115 oC
118 oC
153 oC
189 oC