复旦大学：《物理化学》精品课程教学资源（PPT课件讲稿）第6章 分子间相互作用 Interaction between Molecules

●a Chapter vi Interaction between molecules Physical Chemistry 2021821 Chemistry Departme nt of Fudan Universit

Physical ChemistryI Chapter VI Interaction between Molecules 2021/8/21 Chemistry Department of Fudan University 1 Physical Chemistry

●a Chapter VI Interaction between Molecules,2 86-1 Intermolecular interaction Weak interactions between molecules 1873--van der waals 1910 Noble prize in Physics 2021821 Chemistry Departme nt of Fudan University

Physical ChemistryI Chapter VI Interaction between Molecules 2021/8/21 Chemistry Department of Fudan University 2 §6−1 Intermolecular interaction 1873---van der Waals 1910 Noble Prize in Physics Weak interactions between molecules

Physical Chemistry Chapter VI Interaction between Molecules,2 (1 Electrostatic interaction Keesom 1912 Dipole-dipole interactions between two polar molecules 2+2(40)2k7R] 2021821 Chemistry Departme nt of Fudan University

Physical ChemistryI Chapter VI Interaction between Molecules 2021/8/21 Chemistry Department of Fudan University 3 (1) Electrostatic interaction Keesom 1912 Dipole-dipole interactions between two polar molecules 2 2 2 6 e 1 2 0 2 [ /(4 ) ] 3 E kTR = −   

●a Chapter VI Interaction between Molecules,2 (2)Dipole-Induced-dipole interaction Debye 19201921 A molecule with permanent dipole can induce a dipole of a neighboring polarizability molecule(polarizability a). The interaction of the induced dipole with the permanent dipole can be written as: En=-(a12+a242)(40)2R 2021821 Chemistry Departme nt of Fudan University

Physical ChemistryI Chapter VI Interaction between Molecules 2021/8/21 Chemistry Department of Fudan University 4 (2) Dipole-Induced-dipole interaction Debye 1920-1921 A molecule with permanent dipole can induce a dipole of a neighboring polarizability molecule (polarizability a). The interaction of the induced dipole with the permanent dipole can be written as: 2 2 2 6 p 1 2 2 1 0 E R = − + ( )/(4 ) a  a  

●a Chapter VI Interaction between Molecules,2 For similar molecules,ifa1=02=0,1=μ2=μ,then En=-202/(4e0)2R 2021821 Chemistry Departme nt of Fudan University

Physical ChemistryI Chapter VI Interaction between Molecules 2021/8/21 Chemistry Department of Fudan University 5 For similar molecules, if a1=a2=a, 1=2=, then 2 2 6 p 0 E R = −2 / 4 a  （ ）

Physical Chemistry Chapter VI Interaction between Molecules,2 (3)Dispersion interaction Transient dipole interactions 1930----London E4=-[12(1+l2)aa2/(4xen)2R”] 2021821 Chemistry Departme nt of Fudan University

Physical ChemistryI Chapter VI Interaction between Molecules 2021/8/21 Chemistry Department of Fudan University 6 (3) Dispersion interaction Transient dipole interactions 1930----London 2 6 d 1 2 1 2 1 2 0 3 [ /( )][ / 4 ] 2 E I I I I R = − + a a  （ ）

●a Chapter VI Interaction between Molecules,2 (4)Total Energy of intermolecular interactions up 30,al e=E+e+e p (4)2R‖3k7 +a1h2+h+2(1+I2 2021821 Chemistry Departme nt of Fudan University

Physical ChemistryI Chapter VI Interaction between Molecules 2021/8/21 Chemistry Department of Fudan University 7 (4) Total Energy of intermolecular interactions 2 2 1 2 1 2 1 2 2 2 e p d 1 2 1 2 6 0 1 2 1 2 3 (4 ) 3 2 I I E E E E R kT I I   a a a  a     = + + = − + + +       （ + ）

●a Chapter VI Interaction between Molecules,2 Partition of van der waals interaction molecule Dipole moment Polarizability E Ep E E 10-3C.m 10-40C.m2.V kJ·mol m kJ.mol-l kJ mol-1 0 0.000 0.000 8.49 8.49 CO 0.40 0.003 0.008 8.74 8.75 HI 1.27 6.01 0.025 0.113 25.8 5.9 HBr 2.60 0.686 0.502 219 23.1 HCI 3.43 2.93 3.30 16.8 NH3 5.00 2.46 13.3 14.9 29.8 HO 6.14 165 8.99 ↓7.2 2021821 Chemistry Departme nt of Fudan University

Physical ChemistryI Chapter VI Interaction between Molecules 2021/8/21 Chemistry Department of Fudan University 8 分子 10 C m 30  − 偶极矩 40 2 1 10 C m V − −   极化率 1 e kJ mol −  E 1 p kJ mol −  E 1 d kJ mol −  E 1 kJ mol−  E Ar 0 1.81 0.000 0.000 8.49 8.49 CO 0.40 2.21 0.003 0.008 8.74 8.75 HI 1.27 6.01 0.025 0.113 25.8 25.9 HBr 2.60 3.98 0.686 0.502 21.9 23.1 HCl 3.43 2.93 3.30 1.00 16.8 21.1 NH3 5.00 2.46 13.3 1.55 14.9 29.8 H2O 6.14 1.65 36.3 1.92 8.99 47.2 Partition of van der Waals interaction Dipole moment Polarizability molecule

●a Chapter VI Interaction between Molecules,2 The interaction energy of AB can be obtained using Variational Principle(quantum mechanics) y=④+C1,+C+C2 aB AB aB =+EB+E。+Bn+ E 2021821 Chemistry Departme nt of Fudan University

Physical ChemistryI Chapter VI Interaction between Molecules 2021/8/21 Chemistry Department of Fudan University 9 = +  +  +   AB 1 A B 2 AB 3 A B Ψ Φ C Φ C Φ C Φ e p d 0 B 0 E = EA + E + E + E + E The interaction energy of AB can be obtained using Variational Principle (Quantum mechanics)

●a Chapter VI Interaction between Molecules,2 (5)Intermolecular potential energy B E attr s 6 R rep (n=8-16) R 2021821 Chemistry Departme nt of Fudan University

Physical ChemistryI Chapter VI Interaction between Molecules 2021/8/21 Chemistry Department of Fudan University 10 (5) Intermolecular potential energy attr 6 B E R = − rep n A E R = (n=8-16)