Isomers, etc.

Today was a day to look at how we can assemble atoms into different configurations. The emphasis was on constitutional isomers, compounds which have the same component atoms in the same numbers but are put together through different bonding structures. We spent most of the day trying to put together all of the different constitutional isomers of C5H12, C6H14 and C7H16.

The first modeling exercise has been posted to the left; remember to keep bringing your models to class.

I have another resonance podcast to post. However, a recent "upgrade" to the system now chooses to see the required file type as a threat to the system and is refusing to allow me to upload the file. I am working on getting this resolved.

An Easy Day

Ah, to relax on a Monday morning. A brief intro to the model kit and then a description of how organic chemists have gone to "shorthand" skeletal structures in order to simplify the structures. Major points: carbons are rarely shown but are understood to be at intersections of bonds and at the ends of bonds if no other atoms are indicated; hydrogens on carbons are rarely shown but are understood to be the "missing" items if there aren't four bonds shown to a carbon.

The picture is of a golf ball lounging around, just as we were in class today.

Don't forget to work on putting together a structure of the cocaine molecule with your model kits for Wednesday.

And -- bring models; bring clickers.

Acids and Bases and Equilibria, Oh My!

A good day of chemistry today. The focus was on acid/base chemistry and we learned how to use pKa values to determine which way is the preferred direction in an acid/base reaction at equilibrium. To top it off, we then took that same acid/base reaction and showed how to draw arrows indicating electron movement that led to the transformations shown (in both directions). Using this method allowed us to think of acids as electron pair acceptors (instead of proton donors) and bases as electron pair donors (instead of proton acceptors). This Lewis acid/base definition is much more general and will serve us well over the course of the next 29 weeks of organic chemistry.

Two problem sets were posted and I showed how to subscribe to the chemistry podcasts.

Today's title is inspired by The Wizard of Oz, hence the picture.

BRING YOUR MODELS ON MONDAY!

Podcasts on iTunes

There are a number of podcasts that are posted on iTunes for this course. You can access them by subscribing through iTunes. Open iTunes, select podcasts, and under the "Advanced" menu, choose "Subscribe to podcast." Enter this URL: http://itech.dickinson.edu/blog/?feed=rss2&cat=765

At the moment, most of the podcasts that I have deal with Chem 242 topics but I hope to add to the selection as time goes on. The "Basics of Resonance" podcast is useful for you.

Resonance and Hybridization

Today we learned two important ideas -- hybridization and resonance. Hybridization allows a chemist to explain molecular geometries by showing that we can combine "normal" orbitals into hybrids. The example shown today in class demonstrated how a carbon atom, with valence electrons in 2s and 2p orbitals, can hybridize those orbitals in such a way that the carbon will naturally assume a tetrahedral shape. There are other methods of hybridization that lead to carbon geometries consistent with atoms having double or triple bonds, as well. This material is at the end of chapter one.

We also discussed resonance, which for our purposes now refers to a method of maneuvering electrons in order to demonstrate different contributing structures to an overall structure. The major point to remember here, and the one that is often the most difficult for students, is that the structure does NOT go back and forth between the various resonance forms. Rather the actual structure is some COMBINATION of all possible resonance forms.

The picture is of Milford Beeghly, an Iowa farmer who was a pioneer in developing and selling hybrid corn. His grandson made a movie about him, you can read about it here.

Bring clickers on Friday!

Opening Day!

Today was relatively uneventful -- a brief overview of the syllabus and course grid, a description of the web page and the blog, and other basic information. On Wednesday we'll actually do some chemistry, starting out with a treatment of hybridization, so make sure that you read sections 1.7 - 1.11 in the text.

Welcome!

Welcome to the Dickinson College chemistry 241 blog. Bookmark or subscribe to this site to keep up with all class activities.