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1、(Intermolecular Forces),之物质结构（3）分子间作用力,Dr.Xiaogai Yang Department of Chemical BiologySchool of Pharmaceutical SciencesPeking University,How Drug works,-A majority of pharmacologic responses are mediated through receptors,-Weak Interactions Are Crucial to Macromolecular Structure and Function,云腾致雨 露结
2、为霜,Intermolecular Forces,The boiling point and melting point increase with increasing intermolecular forces.,Molecular polarity,Instantaneous dipole,Permanent dipole,Intermolecular forces are electrostatic forces.,The Origination of Intermolecular Forces,Types of Intermolecular Forces,Orientation Fo
3、rce,Induction Force,London Dispersion Force,H-Bonding,Ion-Dipole Forces,Hydrophobic Interactions,Orientation Force,Dipole Dipole Force,Induction Force,Dipole Induced Dipole Force,London Dispersion Force,Induced Dipole Induced Dipole Force,Polarizability,Dispersion force tends to increase with increa
4、sing molecular mass,Summary,分子间作用能的分配,Exercise,氢键(H-Bonding),XH-Y,an unshared electron pair,One of the smaller atoms,-X 相同,-Y 相同,-X,Y均相同,-A hydrogen bond is an attractive interaction between an unshared electron pair on an electronegative O,N,and F and a positively polarized hydrogen atom bonded to
5、another O,N,or F.,high boiling points,low boiling points,分子间缔合，沸点升高，熔点升高,-可形成分子间或分子内氢键Inter-&intra-molecular hydrogen bond,A water molecule can form up to four hydrogen bonds.,Hydrogen bonding by a water molecule,around a molecule in the solid in the liquid,Structure and Properties of Water,Because
6、of Hydrogen Bonding.Water has a uniquely high specific heat(1 cal/gC)and a uniquely high heat of vaporization(541.6 cal/g).Thermal regulation of the climate.Absorbs heat during the day(vaporization of water)Warms the earth during the night(dew etc.).The density of solid water is less than liquid wat
7、er.Very unusual.This allows life to exist in our oceans and lakes.,DNA 分子中存在氢键,Ion-Dipole Forces,Interaction between an ion(Na+)and a dipole(water).Strongest of all intermolecular forces,Hydrophobic Interactions,-The tendency of nonpolar molecules to self-associate in water defined as hydrophobic ef
8、fect.,Straight flush,Junk,Johns hand,Daves hand,1878年，L.Boltzman提出了熵与微观状态数的关系,S=k lnW W:the number of possible arrangements in the system k:Boltzmanns constant,-The driving force is increased solvent entropy.,Weak Interactions Are Crucial to Macromolecular Structure and Function,H-Bond(10-40)kJ/mol,
9、-Relative strength,Strongly repulsive at short internuclear distances,very weak at long internuclear distances,-Working Range,-Very important in protein folding,results in a great variety of protein shapes&sizes,Properties of Solutions,Colligative Properties1.lowering the Vapor Pressure2.Boiling-Poi
10、nt Elevation3.Freezing-Point Depression4.Osmosis,Factors Affecting Solubility,Dynamic equilibrium,Factors Affecting Solubility,-The solution process,Solvation,Hydration,1.Solute-solute interactions,2.Solvent-solvent interactions,2.Solute-solvent interactions,-Solution Formation,Energy Changes,Sponta
11、neity and Disorder,.Processes in which the energy content of the system deceases tend to occur spontaneously.,.Processes in which the disorder of the system increases tend to occur spontaneously.,NH4NO3,H=26.4kJ/mol,.Substances with similar intermolecular attractive forces tend to be soluble in one
12、another.,-“Like dissolves like”,-CH2-CH2-C-OH,O,-CH-CH3,CH3,Colligative Properties,.Differ from those of the pure solvent.Depend primarily on the concentration not the kind of solute particles,“Depending on the collection”,-The vapor pressure of a liquid is the pressure exerted by its vapor when the
13、 liquid and vapor states are in dynamic equilibrium.,-A nonvolatile solute reduces the rate of vaporization of the solvent.,-The extent to which a nonvolatile solute lowers the vapor pressure is proportional to its concentration.,-Boiling point,Liquids boil when the external pressure equals the vapo
14、r pressure.Two ways to get a liquid to boil:increase temperature or decrease pressure.Normal boiling point is the boiling point at 760 mmHg(1 atm).,-Boiling point is dependent on the intermolecular forcesPolar molecules have higher b.p.than nonpolar molecules,-Freezing point,The freezing point corre
15、sponds to the temperature at which the vapor pressures of the solid and liquid phases are the same.,The Concentration of Solute Particles,#Nonelectrolytes：One mole of a nonelectrolyte produces one mole of solute particlescsolute particles=c#Electrolytes:Exist as ions in solutionProvide more than one
16、 mole of particles per mole of solute dissolvedcs.p.=ic,i is the moles of solute particles per mole solute,1.Lowering the Vapor Pressure,Dissolved solute lowers vapor pressure of solvent.,PA=A PA,Roaults Law,PA:the vapor pressure of the solutionXA:the mole fraction of the solventPA:the vapor pressur
17、e of the pure solvent,Ideal solutions:,Real solutions:,When the solute concentration is low and when the solute and the solvent are much alike in molecular size and in the strength and type of intermolecular attractions.,What you expect for the vapor pressure when the intermolecular forces between s
18、olvent and solute are weaker than those between solvent and solvent and between solute and solute.Conversly,what you expect when the interactions between solute and solvent are exceptionally strong?,Boiling-Point Elevation AndFreezing-Point Depression,DTb=Kb m,DTf=Kf m,Kb:molal boiling-point elevati
19、on constant,m-molality:the number of moles of solute per 1000 g of solvent,Kf:molal freezing-point depression constant,强电解质的依数性偏差(Deviation of Colligative Properties for Strong Electrolytes),电解质稀溶液的依数性:p=iKbB Tb=iKbbB Tf=iKf bB,难挥发的非电解质稀溶液的依数性:p=KbB Tb=KbbB Tf=Kf bB,对AB型强电解质（NaCl）,i2 A2B型（Na2SO4）或AB
20、2型（MgCl2）强电解质，i3(近似值).,i 称校正因子,Molarity(M)=,Amount of solute(in moles)Volume of solution(in liters),Molality(m)=,Amount of solute(in moles)Mass of solvent(in kilograms),An antifreeze solution is prepared containing 40.0 g of ethylene glycol(molar mass=62.0 g/mol)in 60.0 g waterCalculate the freezing
21、 and boiling points of this solution.,Solution:,For water,Kf=1.86 and Kb=0.52,Hence the solution should freeze at 20.1 and boil at 105.6.,4.Osmosis,Diffusion,Microcon Centrifugal Filter Unit,超滤膜(ultra-filtration membrane),透析袋(dialysis tubing),产生渗透条件:,渗透方向：稀溶液 浓溶液,渗透现象会无止境地进行下去吗?,The net movement of
22、solvent is always toward the more concentrated solution.,渗透现象,半透膜,产生渗透原因,-Osmosis Pressure,The Pressure required to prevent osmosis.,PV=nRT P=cRT,Example:Calculate the osmotic pressure of 0.10 mol/Lglucose solution at 25.How about 0.10 mol/L NaCl solution?,Solution:,cos(glucose)=cglucose=0.10 mol/L
23、P(glucose)=cosRT=0.10 x8.31x298=250 kPacos(NaCl)=i c=2x0.10=0.20 mol/L P(NaCl)=0.20 x8.31x298=500 kPa,The unit here is kPa!,Jacobus Henricus vant Hoff1852-1911,例：25时，求0.9%的生理盐水的渗透压是多少？,渗透浓度(Osmolarity),单位:渗透摩尔每升（Osmol/L）或毫渗透摩尔每升（mOsmol),每升溶液中所能产生渗透效应的各物质质点的总浓度,正常人血浆总渗透浓度为 303.7,临床规定,渗透方向：低渗 高渗,-Osmo
24、sis and living cell,Cellular Responds to Body Fluid Tonicity,Isotonic,Hypertonic,Hypotonic,例:1.00 g of heme is dissolved in water and diluted to 100 mL.At 20,the osmotic pressure is measured to be0.366 kPa.Calculate the molar mass of heme.How about the freezing point of the solution?,Solution:,P=cRT
25、;c=P/(RT)=0.366/(8.81x293)=1.50 x10-4 mol/Ln=cV=1.50 x10-4x100 x10-3=1.50 x10-5 molMolar mass=m/n=1.00/1.50 x10-5=6.67x104 g/molDTf=KfbB=Kfc=1.50 x10-4x1.86=2.79x10-4Hence this heme solution should freeze at 0.00,例:1.00 g of heme is dissolved in water and diluted to 100 mL.At 20,the osmotic pressure
26、 is measured to be0.366 kPa.Calculate the molar mass of heme.How about the freezing point of the solution?(Kf=1.86),Important terms,Intermolecular forcesVan der Waals forcesDipole-dipole forcesLondon(dispersion)forcesHydrogen bondingColligative propertiesVapor-pressure-loweringBoiling-point elevatio
27、nFreezing-point depressionOsmosisOsmotic pressure,Review,Atom,Molecule,Substances,Orientation Force,Induction Force,London Dispersion Force,H-Bonding,Ion-Dipole Forces,Hydrophobic Interactions,Solubility,Colligative properties,Increased Entropy,Molecular polarization,Summary of concepts,Summary of concepts,Skills,Identifying intermolecular forcesDetermining the boiling points on the basis of intermolecular forcesCalculating osmotic pressure,boiling-point elevation and freezing-point depression.,Questions 习题,P193:4,6,8,12,14P168:7,8,10,15,THE END,
