[PDF] Van der Waals Forces between Polar Molecules

19121_8vorl21_120124.pdf

ğƓ ķĻƩ ‘ğğƌƭ CƚƩĭĻƭ ĬĻƷǞĻĻƓ tƚƌğƩ ğƓ ķĻƩ ‘ğğƌƭ CƚƩĭĻƭ ĬĻƷǞĻĻƓ tƚƌğƩ aƚƌĻĭǒƌĻƭaƚƌĻĭǒƌĻƭ

ğƓ ķĻƩ ‘ğğƌƭ ŅƚƩĭĻʹ

•ƷŷĻ ƚƩźĻƓƷğƷźƚƓ ŅƚƩĭĻʹ YĻĻƭƚƒ źƓƷĻƩğĭƷźƚƓƭ ƚŅ ƦĻƩƒğƓĻƓƷ ķźƦƚƌĻƭ

•ƷŷĻ źƓķǒĭƷźƚƓ ŅƚƩĭĻʹ 5ĻĬǤĻ źƓƷĻƩğĭƷźƚƓƭʹ ğ ƦĻƩƒğƓĻƓƷ ķźƦƚƌĻ źƓķǒĭĻƭ ğ ķźƦƚƌĻ źƓ ğƓƚƷŷĻƩ ƓƚƓƦƚƌğƩ ƒƚƌĻĭǒƌĻ

•ƷŷĻ ķźƭƦĻƩƭźƚƓ ŅƚƩĭĻʹ

[ƚƓķƚƓ ķźƭƦĻƩƭźƚƓ źƓƷĻƩğĭƷźƚƓƭ ĬĻƷǞĻĻƓ ƷƩğƓƭźĻƓƷ ķźƦƚƌĻƭ ƚŅ ƓƚƓƦƚƌğƩ

•ƷŷĻ ķźƭƦĻƩƭźƚƓ ŅƚƩĭĻʹ

[ƚƓķƚƓ ķźƭƦĻƩƭźƚƓ źƓƷĻƩğĭƷźƚƓƭ ĬĻƷǞĻĻƓ ƷƩğƓƭźĻƓƷ ķźƦƚƌĻƭ ƚŅ ƓƚƓƦƚƌğƩ

ĬǒƷ ƦƚƌğƩźǩğĬƌĻ ƒƚƌĻĭǒƌĻƭ

CƚƩ ƷǞƚ ķźƭƭźƒźƌğƩ ƦƚƌğƩ ƒƚƌĻĭǒƌĻƭʹ

ΛЊБΜ

hƓƌǤ ƷŷĻ ķźƭƦĻƩƭźƚƓ źƓƷĻƩğĭƷźƚƓ ĭƚƓƷƩźĬǒƷĻƭ źŅ ĬƚƷŷ ƒƚƌĻĭǒƌĻƭ ğƩĻ ƓƚƓƦƚƌğƩ͵

ŷǤķƩƚƦŷƚĬźĭ

ĻŅŅĻĭƷ

ğƓ ķĻƩ ‘ğğƌƭ CƚƩĭĻƭ ĬĻƷǞĻĻƓ tƚƌğƩ ğƓ ķĻƩ ‘ğğƌƭ CƚƩĭĻƭ ĬĻƷǞĻĻƓ tƚƌğƩ aƚƌĻĭǒƌĻƭaƚƌĻĭǒƌĻƭ

ΛЊБΜ

ΛЊБΜ ŷğƭ ƌźƒźƷĻķ ǝğƌźķźƷǤʹ

•ƭŷƚǒƌķ ĭƚƓƭźķĻƩ ƨǒğķƩǒƦƚƌğƩ ğƓķ ŷźŭŷĻƩΏƚƩķĻƩ ƒǒƌƷźƦƚƌĻ źƓƷĻƩğĭƷźƚƓƭ

•źƓ Ʃźŭźķ ƒĻķźğ ƷŷĻ ķźƦƚƌĻΑķźƦƚƌĻ źƓƷĻƩğĭƷźƚƓ źƭ ƦƩƚƦƚƩƷźƚƓğƌ Ʒƚ ЊΉƩЌ

•ƭŷƚǒƌķ ĭƚƓƭźķĻƩ ƷŷĻ źƓƷĻƩğĭƷźƚƓ ƚŅ ƷŷƩĻĻ ΛƚƩ ƒƚƩĻΜ ƒƚƌĻĭǒƌĻƭ

ΛЊВΜ

ğ ў !ǣźƌƩƚķΑĻƌƌĻƩ ŅƚƩƒǒƌğ

•ƒƚƌĻĭǒƌĻƭ ğƩĻ ƭƨǒĻĻǩĻķ ƷƚŭĻƷŷĻƩʹ ƷŷĻ ƓǒĭƌĻğƩ ğƓķ ĻƌĻĭƷƩƚƓźĭ ƩĻƦǒƌƭźƚƓƭ ķƚƒźƓğƷĻ ƷŷĻ ğƷƷƩğĭƷźǝĻ ŅƚƩĭĻƭ

ğƓ ķĻƩ ‘ğğƌƭ CƚƩĭĻƭ ĬĻƷǞĻĻƓ tƚƌğƩ ğƓ ķĻƩ ‘ğğƌƭ CƚƩĭĻƭ ĬĻƷǞĻĻƓ tƚƌğƩ aƚƌĻĭǒƌĻƭaƚƌĻĭǒƌĻƭ

aźĻ ƦƚƷĻƓƷźğƌʹ wĻƦǒƌƭźƚƓƭ !ƷƷƩğĭƷźƚƓƭ

ĻǣƦ

ΏЏ ƦƚƷĻƓƷźğƌ

ŷğƩķΏƭƦŷĻƩĻ ƦƚƷĻƓƷźğƌʹ

σǝğƓ ķĻƩ ‘ğğƌƭ ƦğĭƉźƓŭ Ʃğķźǒƭ

wĻƦǒƌƭźƚƓƭ !ƷƷƩğĭƷźƚƓƭ

ĻǣƦ

ΏЏ ƦƚƷĻƓƷźğƌ

[ĻƓƓğƩķΏWƚƓĻƭ ƦƚƷĻƓƷźğƌʹ wĻƦǒƌƭźƚƓƭ !ƷƷƩğĭƷźƚƓƭ

ƭǒƒ ƚŅ σ

wĻƷğƩķğƷźƚƓ wĻƷğƩķğƷźƚƓ ĻŅŅĻĭƷƭĻŅŅĻĭƷƭ ƚŅƚŅ ķźƭƦĻƩƭźƚƓķźƭƦĻƩƭźƚƓ ŅƚƩĭĻƭŅƚƩĭĻƭ

! . w ν .

ЋwΉ ĭ ѢѢ ΛΔ9Ήŷ ΜΏЊ ķźƭƦĻƩƭźƚƓ źƓƷĻƩğĭƷźƚƓ źƭ ǞĻğƉĻƓĻķ

w β ЊЉЉ ƓƒͲ

ЋwΉ ĭ ѡѡ ΛΔ9ΉŷΜΏЊ ƷŷĻ ĭƚƩƩĻƌğƷźƚƓ ƚŅ ƷŷĻ ķźƦƚƌĻƭ źƭ

ƦĻƩŅĻĭƷ

Van der Waals MoleculesVan der Waals Molecules

ǝğƓ ķĻƩ ‘ğğƌƭ ƒƚƌĻĭǒƌĻƭʹ IĻЋͲ bĻЋͲ !ƩЋͲ -Ļ/ƌͲ !ƩCͲ bğ!ƩͲ !ƩΏ/h

ķźƒĻƩƭΛbI

ЌΜЋͲ Λ/ЏIЏΜЋͲ Λ/ЏIЏΜ!Ʃ͵ .

Van der Waals MoleculesVan der Waals Molecules

Van der Waals Van der Waals MoleculesMolecules

bğYƩ

ĬƚƓķ ĻƓĻƩŭǤʹ

ƷŷƩĻĻ ƚƩķĻƩƭ ƚŅ ƒğŭƓźƷǒķĻ ƌğƩŭĻƩ

АВЉĭƒΏЊў ВВ ƒĻ

АЉĭƒ

ΏЊў Б͵Б ƒĻ

Van der Waals Van der Waals MoleculesMolecules

ǝğƓ ķĻƩ ‘ğğƌƭ ƒƚƌĻĭǒƌĻƭ ƚŅƷĻƓ ĻǣŷźĬźƷ ƓƚƓƩźŭźķ ƭƷƩǒĭƷǒƩĻƭʹĭğƓ ğƌƷĻƩ ƷŷĻźƩ ƓǒĭƌĻğƩ

ŅƩğƒĻǞƚƩƉ ƦĻƩźƚķźĭğƌƌǤ͵

ŷĻƩĻ ĻǣźƭƷ ƭĻǝĻƩğƌ źƭƚƒĻƩƭ ǞźƷŷ ƭƌźŭŷƷƌǤ ķźŅŅĻƩĻƓƷ ŭƩƚǒƓķΏƭƷğƷĻ ĻƓĻƩŭźĻƭ

ΛbIЌΜ Ћ

ΛhЋΜ Ћ ʹƷŷĻ ƩĻĭƷğƓŭǒƌğƩ ƭƷƩǒĭƷǒƩĻ ŷğƭ ƷŷĻ ƌğƩŭĻƭƷ ĬźƓķźƓŭ ĻƓĻƩŭǤ

[ğƩŭĻ ƒĻğƓ źƓƷĻƩƓǒĭƌĻğƩ ķźƭƷğƓĭĻʹ ƌğƩŭĻ ƒƚƒĻƓƷƭ ƚŅ źƓĻƩƷźğğƩĻ ƌğƩŭĻͲ ğƓķ ƭƒğƌƌ

ƩƚƷğƷźƚƓğƌ ĭƚƓƭƷğƓƷƭʹ ƌƚǞ ƷĻƒƦĻƩğƷǒƩĻƭ ğƩĻ ƓĻĻķĻķ Ʒƚ ƩĻƭƚƌǝĻ ƷŷĻ ĭƌƚƭĻƌǤ ƭƦğĭĻķ

ƩƚƷğƷźƚƓğƌ ƌźƓĻƭ The Unique Properties of WaterThe Unique Properties of Water

ƌźƨǒźķ

•ŷźŭŷ ƒĻƌƷźƓŭ ğƓķ ĬƚźƌźƓŭ ƦƚźƓƷƭ

•ķĻƓƭźƷǤ ƒğǣźƒǒƒ ğƷ Ѝπ/ ĻǣŷźĬźƷĻķ ĬǤ ƌźƨǒźķ ǞğƷĻƩ

•ǝĻƩǤ ƌƚǞ ĭƚƒƦƩĻƭƭźĬźƌźƷǤ

•ǒƓǒƭǒğƌ ƭƚƌǒĬźƌźƷǤ ƦƩƚƦĻƩƷźĻƭ ĬƚƷŷ ğƭ ğ ƭƚƌǒƷĻ ğƓķ ğƭ ğ ƭƚƌǝĻƓƷ

źĭĻ

ŷĻƭĻ ƦƩƚƦĻƩƷźĻƭ ƚŅ ǞğƷĻƩ ƦƚźƓƷ Ʒƚ ƷŷĻ ĻǣźƭƷĻƓĭĻ ƚŅ ğƓ źƓƷĻƩƒƚƌĻĭǒƌğƩ źƓƷĻƩğĭƷźƚƓ ƷŷğƷ źƭ

ƭƷƩƚƓŭĻƩ ƷŷğƓ ƷŷğƷ ĻǣƦĻĭƷĻķ ŅƚƩ ƚƩķźƓğƩǤͲ ĻǝĻƓ ŷźŭŷƌǤ ƦƚƌğƩͲ ƌźƨǒźķƭ͵

The Unique Properties of Water: CohesionThe Unique Properties of Water: Cohesion

Θ !ƷƷƩğĭƷźƚƓ ĬĻƷǞĻĻƓ ƦğƩƷźĭƌĻƭ ƚŅ ƷŷĻ ƭğƒĻ ƭǒĬƭƷğƓĭĻ Λ ǞŷǤ ǞğƷĻƩ źƭ ğƷƷƩğĭƷĻķ Ʒƚ źƷƭĻƌŅΜ

•wĻƭǒƌƷƭ źƓ {ǒƩŅğĭĻ ƷĻƓƭźƚƓ Λğ ƒĻğƭǒƩĻ ƚŅ ƷŷĻ ƭƷƩĻƓŭƷŷ ƚŅ ǞğƷĻƩ͸ƭ ƭǒƩŅğĭĻΜ

Θ tƩƚķǒĭĻƭ ğ ƭǒƩŅğĭĻ Ņźƌƒ ƚƓ ǞğƷĻƩ ƷŷğƷ ğƌƌƚǞƭ źƓƭĻĭƷƭ Ʒƚ ǞğƌƉ ƚƓ ƷŷĻ ƭǒƩŅğĭĻ ƚŅ ǞğƷĻƩ

The Unique Properties of Water: AdhesionThe Unique Properties of Water: Adhesion

•!ƷƷƩğĭƷźƚƓ ĬĻƷǞĻĻƓ ƷǞƚ ķźŅŅĻƩĻƓƷ ƭǒĬƭƷğƓĭĻƭ͵

Θ /ğƦźƌƌğƩǤ ğĭƷźƚƓΏǞğƷĻƩ ƒƚƌĻĭǒƌĻƭ Ǟźƌƌ ͻƷƚǞͼ Ļğĭŷ ƚƷŷĻƩ ğƌƚƓŭ ǞŷĻƓ źƓ ğ ƷŷźƓ ŭƌğƭƭ

ƷǒĬĻ͵

Θ 9ǣğƒƦƌĻʹ ƷƩğƓƭƦźƩğƷźƚƓ ƦƩƚĭĻƭƭ Ǟŷźĭŷ ƦƌğƓƷƭ ğƓķ ƷƩĻĻƭ ƩĻƒƚǝĻ ǞğƷĻƩ ŅƩƚƒ ƷŷĻ ƭƚźƌͲ

ğƓķ ƦğƦĻƩ ƷƚǞĻƌƭ ƭƚğƉ ǒƦ ǞğƷĻƩ͵

Water MoleculeWater Molecule

‘ğƷĻƩƒƚƌĻĭǒƌĻ źƭ ǝĻƩǤ ƦƚƌğƩͲ ğƓķ ŭĻƷƭ ĻǝĻƓ ƒƚƩĻ ƦƚƌğƩ źƓ ƷŷĻ ĭƚƓķĻƓƭĻķ ƦŷğƭĻ͵

Condensed WaterCondensed Water

ŷĻ ƦƩƚƷƚƓ ĭƚƓķǒĭƷźǝźƷǤ ğƓķ ƒƚĬźƌźƷǤ źƓ źĭĻ źƭ ŷźŭŷĻƩ ƷŷğƓ źƓƷŷĻ ƌźƨǒźķʹ

ƷŷĻ źĭĻ ƌğƷƷźĭĻ ğŅŅƚƩķƭ ƦğƷŷǞğǤƭ ŅƚƩ ƷŷĻ ƒƚǝĻƒĻƓƷ ƚŅ ĭŷğƩŭĻƭΏ

ŷǤķƩƚŭĻƓ ĬƚƓķźƓŭ ƓĻƷǞƚƩƉ ͵

Hydrogen Hydrogen bondbond

Hydrogen Hydrogen bondbond

źƓƷƩğƒƚƌĻĭǒƌğƩ IΏĬƚƓķźƓƷĻƩƒƚƌĻĭǒƌğƩ IΏĬƚƓķ

ƒƚƌĻ

[źƷĻƩğƷǒƩĻʹ

Hydrogen Hydrogen bondbond

bond d[Å] -------------

O-H ••• O 2.7

O-H ••• O

- 2.6

O-H ••• N 2.9

N-H ••• O 3.0

N +-H ••• O 2.9

N-H ••• N 3.1Θ ŷĻ ƭŷƚƩƷĻƩ ƷŷĻ IΏĬƚƓķͲ ƷŷĻ ƭƷƩƚƓŭĻƩ ƷŷĻ ĬƚƓķͳ ƷǤƦźĭğƌ ķźƭƷğƓĭĻƭ

ĬĻƷǞĻĻƓ ķƚƓƚƩ ğƓķ ğĭĭĻƦƷƚƩ ğƩĻ Ћ͵Џ Ʒƚ Ќ͵Њ ) ΛķĻƦĻƓķƭ ƚƓ ƷŷĻ

źƓǝƚƌǝĻķ ğƷƚƒƭ ğƓķ ƷŷĻźƩ ĭŷğƩŭĻΜ͵

{ƷƩǒĭƷǒƩĻ ƚŅ źĭĻ

ŷĻ ŷǤķƩƚŭĻƓ ĬƚƓķƭ ğƩĻ ƭŷƚƩƷĻƩ źƓ źĭĻ ΛЋ͵АÅΜ ƷŷğƓ ĬĻƷǞĻĻƓ źƭƚƌğƷĻķ IЋh ķźƒĻƩƭ ΛЋ͵БЋÅ)ĬĻĭğǒƭĻ

ƚŅ

ĭƚƚƦĻƩğƷźǝźƷǤ͵ /ğƷźƚƓ aƚĬźƌźƷǤ Ή ĭƒ

ЋћЊƭћЊ

bI

Ѝњ

Љ͵АЏЌќЊЉ

ћЌ

bğ њ

Љ͵ЎЊВќЊЉ

ћЌ

Yњ

Љ͵АЏЋќЊЉ

ћЌ

Iњ

Ќ͵ЏЋќЊЉ

ћЌ

ProtonatedProtonated WaterWater MoleculesMolecules ƦƩƚƷƚƓ ŷƚƦƭʹ Њ͵Ў Ʀƭ œǒƓķĻƌ ĭğƷźƚƓʹ

IЎhЋњ

9źŭĻƓ ĭğƷźƚƓ

IВhЍњ

œǒƓķĻƌ ĭğƷźƚƓʹ

IЎhЋњ

ProtonatedProtonated WaterWater MoleculesMolecules

ŷĻ

ķĻ .ƩƚŭƌźĻ ǞğǝĻƌĻƓŭƷŷ ƚŅ ƷŷĻ ƦƩƚƷƚƓ źƭ Њ͵Ў !πʹ β ķźƭƷğƓĭĻƭ ƚŅ ƦƩƚƷƚƓ ƷƩğƓƭŅĻƩ ƩĻğĭƷźƚƓƭʹ

ƷǒƓƓĻƌźƓŭ ͪ

IǤķƩƚƦŷƚĬźĭ źƓƷĻƩğĭƷźƚƓIǤķƩƚƦŷƚĬźĭ źƓƷĻƩğĭƷźƚƓΘ ĻƌĻĭƷƩƚƭƷğƷźĭͲ IΏĬƚƓķ ğƓķ ǝğƓ ķĻƩ ‘ğğƌƭ źƓƷĻƩğĭƷźƚƓƭ ĬĻƷǞĻĻƓ ƒƚƌĻĭǒƌĻƭ źƓ ğƓ ğƨǒĻƚǒƭ

ĻƓǝźƩƚƓƒĻƓƷ ğƩĻ ĭƚƒƦĻƷĻķ ĬǤ ƷŷĻ źƓƷĻƩğĭƷźƚƓƭ ĬĻƷǞĻĻƓ ƒƚƌĻĭǒƌĻƭ ğƓķ ƷŷĻ ǞğƷĻƩ

ƭǒƩƩƚǒƓķźƓŭ ƷŷĻƒ͵

•ĬǒƷʹ ƓƚƓƦƚƌğƩ ƒƚƌĻĭǒƌĻƭ ƒğƉĻ ǒƓŅğǝƚƩğĬƌĻ źƓƷĻƩğĭƷźƚƓƭ ǞźƷŷ ǞğƷĻƩ͵

•ŷǤķƩƚƦŷƚĬźĭ źƓƷĻƩğĭƷźƚƓ

ʹ ƷŷĻ ƦƩĻŅĻƩĻƓĭĻ ƚŅ ƓƚƓƦƚƌğƩ ƒƚƌĻĭǒƌĻƭ ŅƚƩ ƓƚƓğƨǒĻƚǒƭ

ĻƓǝźƩƚƓƒĻƓƷƭ

Θ ķƩźǝĻƓ ĬǤ ĻƓƷƩƚƦǤʹ źƓƷĻƩğĭƷźƚƓ ƚŅ ŷǤķƩƚƦŷƚĬźĭ ΛƓƚƓƦƚƌğƩΜ ƩĻƭźķǒĻƭ ǞźƷŷ ǞğƷĻƩ źƭ ƌĻƭƭ

ŅğǝƚƩğĬƌĻ ğƭ ǞğƷĻƩ ΑǞğƷĻƩ źƓƷĻƩğĭƷźƚƓƭ

Θ ƒğƆƚƩ ŅğĭƷƚƩ źƓ ƷŷĻ ƭƷğĬźƌźƷźĻƭ ƚŅ ƦƩƚƷĻźƓƭ

ƓΏĬǒƷğƓĻ Λ/ЍIЊЉΜ

The "The "hydrophobichydrophobic" " effecteffectͻĭƌğƷŷƩğƷĻ ĭğŭĻƭͼ

•ƩĻƭǒƌƷ ƚŅ ƷŷĻ ǒƓŅğǝƚƩğĬƌĻ ĭŷğƓŭĻ źƓ ĻƓƷƩƚƦǤ

•ƩĻƚƩźĻƓƷğƷźƚƓ ƚƩ ƩĻƭƷƩǒĭƷǒƩźƓŭ ƚŅ ƷŷĻ ǞğƷĻƩ ƒƚƌĻĭǒƌĻƭ ƭƚ ƷŷĻǤ ĭğƓ ƦğƩƷźĭźƦğƷĻ źƓ IΏ

ĬƚƓķ ŅƚƩƒğƷźƚƓ •ǞğƷĻƩΏƚƩķĻƩźƓŭ ĻŅŅĻĭƷ