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CHEM 433 - 9/15/11

CHEM 433 - 9/15/11. I. Introductory Topics C. Intermolecular Forces (handout, 18.1.-18.5) Conceptual overview cont. —> Recognizing IMF Quantitative Considerations - Energy Scales - Functional forms -Structural Considerations - Adding the repulsive Part

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CHEM 433 - 9/15/11

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  1. CHEM 433 - 9/15/11 I. Introductory Topics C. Intermolecular Forces (handout, 18.1.-18.5) Conceptual overview cont. —> Recognizing IMF Quantitative Considerations - Energy Scales - Functional forms -Structural Considerations - Adding the repulsive Part Read: Start Chapter 1 of Atkins HW #2 via e-mail.. Today or tomorrow AM

  2. Three key questions for identifying IMF? 1) Are ions present? 2) Are polar molecules present? 3) Are there molecules with OH, NH, or FH bonds? Identify i) all and ii) the most significant IMF in the following liquids or mixtures? CH3OH (l), C6H6 (l), O2(aq), KBr(aq), Kr(l) D-ID* DISP D-D H-B Ion-D* DISP D-D H-B DISP* DISP D-D H-B* DISP*

  3. CO2 CCl4

  4. Structural Considerations: Bond Radii http://en.wikipedia.org/wiki/Covalent_radius http://en.wikipedia.org/wiki/Van_der_Waals_radius http://periodictable.com/Properties/A/VanDerWaalsRadius.v.html Rvdw (Ar) =

  5. A 2-minute H-Bonding Case Study: “HF Dimer”or (HF)2 R(HF) = 0.919 Å • E(H-Bond) = 3.6 kcal/mol (15.1 kJ/mol) • R(H…F) = 1.834 Å (non bond R is ~ 2.7 Å !!!) • Donor Bond lengthens: R(HF, “A”) = 0.924 Å • Charge rearrangement: - more polarity - partial e- transfer (0.05 e-) B A Data are from a quantum chemical computation… (MP4/aug-cc-pVTZ)

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