chem 433 - 9/15/11
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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 - PowerPoint PPT PresentationTRANSCRIPT
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
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?
DISPD-DH-B*
DISP* Ion-D*DISPD-DH-B
DISP*
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*DISPD-DH-B
CO2
CCl4
Structural Considerations: Bond Radii
1) http://en.wikipedia.org/wiki/Covalent_radius
2) http://en.wikipedia.org/wiki/Van_der_Waals_radius
http://periodictable.com/Properties/A/VanDerWaalsRadius.v.html
Rvdw (Ar) =
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-)
AB
Data are from a quantum chemical computation… (MP4/aug-cc-pVTZ)