PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Δμi = ΔHi – TΔSi00 0--A---B A + Bq2. Intermolecular interactionsFundamentals of Distribution Separations (II)(08/26/13)1. Principles of distribution equilibria= exp -Δμi - Δμi0RTextKdG -S dT + V dP + Σ(µi + µi )dni**=int extdistribution coefficient (open systems under externalfield)Intermolecular InteractionsIntermolecular interactions:Dissociation of H2O = 200 kcal/mol (H2O 2 H + O)Vaporization energy of H2O = 9.7 kcal/mol (H2Ol H2Og )Intermolecular interactions are weaker than intramolecular interactions, butIt is determining solubility, boiling points, vapor pressure, melting points….These properties are of importance in determining the behavior of compound in chromatography and other separation methodsA useful general principle in separation is like dissolves like. In other words, a molecule will interaction most strongly with the phase or solvent that is most similar to it in its chemical characters.Question: glucose (1) Hexane (1) naphthalene (2) Water (2)4. Hydrogen bond5. Lewis acid-base interactionsElectrostatic interaction (Coulombic) Electron transfer (sharing electron) (hard interactions)(soft interactions)1. Dipole-dipole interactionIntermolecular InteractionsrThe intermolecular interactions can either be attactive or repulsive in nature.Etotal = A/r12 – ΣB/rz Where: E total = net total energy of interactions A = constant describing repulsive forces between i and j B = constant describing attractive forces between i and j z = constant for a given type of attractive force Lennard-Jones potential: z=6i j2. Induction interaction3. Dispersion interaction (London forces)van der Waals forces1. Dipole-dipole interaction+-+-+--+ijijED = -µiµj223 (4 π ε0)2 kTr6µi,µj = dipole moments of i and jT = Temperaturek = Boltzmann’s constantNote: Temperature dependent2. Induction interaction+-+-+-ijijEI = -µiαj2 (4 π ε0)2 r6µi = dipole moments of i αj = polarizability of j Note: independent of temperatureij3. Dispersion interactions (London Force)ijij+-+--+EL = -CL Vi (αi)v (αi)v-αiαj3 hνEL = -4 (4 π ε0)2 r6αi, αj = polarizability of i and j r = distanceh = Plank’s constant ν = Frequency of light required for ionization of each speciesε0 = dielectric permittivity of the medium two atomstwo molecules(αi)v (αi)v = polarizability of i and j per unit volume CL: Dispersion constant (uniform for most compounds)Vi = Molar volume of i (MW/density)Non-covalent bond forms between a molecule with a proton donor groupAnd proton acceptor group.(a) Common proton donors are –OH, -NH, and –SH(b) Common proton acceptor are –O-, =N-, -F, -S-, -Cl, C=C…..(c) E ~ 1/r6(d) Hydrogen bond is one example of a more general class of Lewis acid-base interactions. A + :B A:B4. Hydrogen bonds5. Lewis acid-base interactions(A) Electrostatic interaction (Coulombic) (hard interactions)(1) Coulombic interactionEAB = 4 π ε0 rQiQj+-ij(2) Interactions with polar and non-ionic compounds (ED)ED = -Qiµj226 (4 π ε0)2 kTr4(3) Interactions with non-polar compounds (EL)EL = -Qiαj222 (4 π ε0)2 r4(B) Electron transfer (sharing electron) (soft interactions)+ij+ijnon-polarpolar5. Lewis acid-base interactionsEAB = - [EA* EB + CA* CB], Approximation for A-B interaction Where: EA* EB = Measures of acid (A) and base (B)’s ability to undergo hard acid-base interaction CA* CB = Measures of acid (A) and base (B)’s ability to undergo soft acid-base interactionThe values of EA, EB, CA, CB:Rel. AcidityRel. BasicityEACAEBCBHF 17.0 0.0Alcohols 3.6 0.8Phenols 4.7 1.7SO2 1.1 7.2Iodine 1.0 10.0Ammonia 1.3 0.3Ketones 0.7 0.11’ Amines 1.2 0.62’ Amines 0,9 0,93’ Amines 0,6 1.2 Esters 0.6 0.4Sulfides 0.0 0.8Strong interactions: hard-hard interactions, and soft-soft interactionsWeak interactions: hard-soft interactions.Δμi = ΔHi – TΔSi00 0--A---B A + Bq= exp -Δμi - Δμi0RTextKdistribution coefficient Distribution equilibria and SolubilitySolubility: ΔG = ΔH – TΔSΔH = Δμ0– TΔS = RT ln (Ci)i dissolved in j ΔG = Δμ + RT ln (Ci)0At soluble equilibrium: ΔG = Δμ + RT ln (Ci) = 0 Ci= exp -Δμ0RT0ΔH = EL +EI + ED + EABΔμi = ΔHi – TΔSi00 0--A---B A + BqΔH = EL +EI + ED + EABDistribution equilibrium and SolubilityAcid-base compoundsNon Acid-base Permanent dipole momentPolar compoundsNon-Polar compoundsType of CompoundsPossible interactions Relative strengthELEL, EI, ED, EABEL, EI, EDWeakStrongFor all of the above interactions are present in one compoundsEL < EI < ED < EABQuantitative Approach for the Strength of Molecular InteractionsA more quantitative approach in estimating the strength of molecular interactions is to use various scales that decribe molecular polarity.(a) Polarizability(b) Dipole Moments(c) Solubility parameters(a) Polarizability(1) The polarizability (α)of a compound is a measure of how easily the electron clouds of a compound may be distorted(2) The value of α for any atom or molecules can be calculated fromspectroscopica properties, such as its refractive index. (αi)v = [3 π N/4][(n2-1)/(n2+2)] Where, (αi)v = polarizability of the compound per unit volumeN = Avogadro’s numbern = refractive index of the compoundsEL = - CL Vi (αi)v (αi)v-two moleculesWhere: (αi)v (αi)v = polarizability of i and j per unit volume CL: Dispersion constant (uniform for most compounds)Dispersion interaction (London forces)Note: it is useful in predicting boiling points and solubility of non-polarcompounds, such as saturated aliphatics. Ethane 30.07 0.572 1.0377 -88.6Octane 114.23 0.7025 1.3974 125.7CompoundMW(g/mol)Density(g/mL)RefractiveIndexBoiling Points(oC)Vi = Molar volume of i