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Use whereby to video-conference in the scienceheaven virtual room.
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Click on Image to download Check-off List for Week 6
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Click to Print out Chapter 2 Learning Outcomes

Upcoming Assignments

Mon/ Tues class -
Oct 7th/ 8th
  • Test #2 - covering Chapter 2
  • Chapter 2 Homework
  • Mayonnaise laboratory

Welcome to Week 6 of PEP, and the continuation through Chapter 2.

Updated September 26th, 2019
Recollect that this is your landing page for announcements and current news for your organic chemistry class. Please check this page often.

Week 5 Summary

PictureFigure 2-12
This week we continued through Chapter 2 - Three-Dimensional Geometry, Intermolecular Interactions, and Physical Properties, examining the impact of polar bonds on permanent dipoles and how we can examine the cumulative effect of dipoles in a molecule to ascertain whether the molecule itself is polar. 

On Wednesday/ Thursday you were asked to identify various functional groups within 3-D models. This coming week, you will be asked to produce functional group names from your memory (no word bank at all) to identify functional groups in line structures.

Recollect from last weeks classes and videos, what you learned about the following intermolecular interactions:
  1. ion-ion interactions - the strongest because ions have very high concentrations of positive and negative charges.
  2. dipole-dipole interactions - occur when the positive end of one molecule's net dipole is attracted to the negative end of another's, as shown in Figure 2-12 (right).
  3. hydrogen bonding - are a form of dipole-dipole interaction occurring between a hydrogen-bond donor (hydrogen atom covalently bonded to F, O, or N, and hydrogen-bond acceptor (any atom with a large concentration of negative charge and lone pair of electrons, which is really only F, O, and N).
  4. Induced dipole-induced dipole (London Dispersion Forces) - are the dominant intermolecular interaction between nonpolar molecules. These occur because at a given instant of time, there will be more electrons on one side of a molecule than on the other; the extra electrons give rise to an instantaneous dipole, which can in turn, impact the electron distribution on an adjacent molecule (Figure 2 - 17, page 95 in text).
  5. Ion-dipole interactions - interactions between dissolved ions and polar solvents, such as what we would see when NaCl dissolves in water.
These intermolecular interactions are important to know and understand because they impact the physical and chemical properties of the molecules themselves.

What to expect in Week 6

During Week 5 we explored the intermolecular interactions between molecules, and how these impact various physical properties. In Week 6, we'll examine two main topics of interest that are the consequence of intermolecular interactions: Solubility of compounds in water and other solvents (Section 2.7), and ranking relative boiling points of structurally similar compounds. As an example, suppose you were to rank the boiling points of the below compounds from lowest to highest:
The first step to ranking these is to consider the most significant intermolecular interactions between molecules of each compound, then group these as:
  • nonpolar compounds that participate principally in London dispersion forces
  • polar compounds capable of hydrogen bonding
  • polar compounds that participate largely in dipole-dipole interactions
Rank the boiling points within each group. Then combine the array accordingly:
Note that all the above compounds possess a benzene ring, making their structures very similar. It is the substituents attached that provide differences with respect to chemical and physical properties.
Image Credits:
Nanocar ball-and-stick model in banner retrieved from: http://news.rice.edu/2015/12/14/rice-to-enter-first-international-nanocar-race/
Nanocar with fullerene wheels in banner by Materialscientist at en.wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=16454593
Glucose ball-and-stick model retrieved from: https://www.thoughtco.com/pathway-most-atp-per-glucose-molecule-608200