structure and molecular properties
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Structure and Molecular Properties
Summer 2012
Overview
• Syllabus• ChemDraw• Structures and intermolecular forces
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
O CH2Cl2 O CH3OHO
hexanes Ethyl acetate (EtOAC)
ethanol acetonitrile water
69 oC 77 oC 78 oC 82 oC 100 oC
O
O
OHCH3CN H2O
toluene Pyridine (pyr) Acetic acid Dimethyl formamide (DMF)
Dimethylsulfoxide (DMSO)
111 oC 115 oC 118 oC 153 oC 189 oC
N
OH
ONO
S
O
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
O CH2Cl2 O CH3OHO
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
O
O
OHCH3CN H2O
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
N
OH
ONO
S
O
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
O CH2Cl2 O CH3OHO
hexanes Ethyl acetate (EtOAC)
ethanol acetonitrile water
69 oC 77 oC 78 oC 82 oC 100 oC
O
O
OHCH3CN H2O
toluene Pyridine (pyr) Acetic acid Dimethyl formamide (DMF)
Dimethylsulfoxide (DMSO)
111 oC 115 oC 118 oC 153 oC 189 oC
N
OH
ONO
S
O
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
O CH2Cl2 O CH3OHO
hexanes Ethyl acetate (EtOAC)
ethanol acetonitrile water
69 oC 77 oC 78 oC 82 oC 100 oC
O
O
OHCH3CN H2O
toluene Pyridine (pyr) Acetic acid Dimethyl formamide (DMF)
Dimethylsulfoxide (DMSO)
111 oC 115 oC 118 oC 153 oC 189 oC
N
OH
ONO
S
O
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
O CH2Cl2 O CH3OHO
hexanes Ethyl acetate (EtOAC)
ethanol acetonitrile water
69 oC 77 oC 78 oC 82 oC 100 oC
O
O
OHCH3CN H2O
toluene Pyridine (pyr) Acetic acid Dimethyl formamide (DMF)
Dimethylsulfoxide (DMSO)
111 oC 115 oC 118 oC 153 oC 189 oC
N
OH
ONO
S
O
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
O CH2Cl2 O CH3OHO
hexanes Ethyl acetate (EtOAC)
ethanol acetonitrile water
69 oC 77 oC 78 oC 82 oC 100 oC
O
O
OHCH3CN H2O
toluene Pyridine (pyr) Acetic acid Dimethyl formamide (DMF)
Dimethylsulfoxide (DMSO)
111 oC 115 oC 118 oC 153 oC 189 oC
N
OH
ONO
S
O
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