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
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
CHEM 433 - 9/15/11
I. Introductory Topics
C. Intermolecular Forces (handout, 18.1.-18.5)
Conceptual overview cont.
—> Recognizing IMF
- Energy Scales
- Functional forms
- 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?
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)
Structural Considerations: Bond Radii
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
• 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-)
Data are from a quantum chemical computation… (MP4/aug-cc-pVTZ)