Author Archives: alan

Huckel's rule, aromatic character, and molecular orbitals

Posted on November 26, 2008 by alan

Today's lecture tried to tie Huckel's rule to a number of topics, including:aromatic character, a more nuanced way of talking about aromaticitycharge distributions and geometryevaluation of "minor" resonance structuresmolecular orbital theoryYou can see all of the slides that were used… Continue reading →

Posted in Post-lecture | 2 Comments

Supersized ferrocene impossible?

Posted on November 18, 2008 by alan

Ferrocene and acetylferrocene, the compounds featured in our current lab experiment, are examples of sandwich compounds or metallocenes. A metallocene of some sort has been made with every transition metal in existence, but double metallocenes in which two organic rings… Continue reading →

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Alkene pi orbital energies

Posted on November 14, 2008 by alan

A question on today's conference problem set asked you to predict how the energies of the pi and pi* orbitals of a typical alkene would respond to twisting the alkene.Valence bond fans: The VB model doesn't contain "pi" or "pi*"… Continue reading →

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Models of Chemical Bonding

Posted on November 12, 2008 by alan

Today I decided to re-trace my steps on Monday and provide a more complete description of chemical bonds through the eyes of molecular orbital theory. A list of take-home lessons from this presentation:MO models contain new orbitals (molecular orbitals), while… Continue reading →

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Halloween Pumpkins

Posted on November 5, 2008 by alan

Halloween fell on Friday this year so I should have been expecting a "trick" or "treat" when I arrived at lecture. Little did I know that I would get both.Everyone was seated in the dark when I arrived and two… Continue reading →

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Bromonium ions

Posted on November 5, 2008 by alan

Here are pictures of the models that I shared with you in class on Monday. They address different issues.Model #1 – A Stable Bromonium Ion. A bromonium can be stabilized by placing large groups around the alkene. These groups offer… Continue reading →

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Back side attack & HOMO-LUMO overlap

Posted on October 13, 2008 by alan

I made two points about the 3-D aspects of nucleophilic substitution today in lecture:the bimolecular reaction that I described (aka SN2) occurs by "backside attack". This is an experimental observation that has been made hundreds (probably tens of thousands) of… Continue reading →

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C7 H10 O3 contest – Week #3 Results

Posted on September 29, 2008 by alan

The final week of the C7 H10 O3 contest brought in two entries. Gabe Holt and Patrick Fink had submitted an entry during week #1, but all of the other participants were brand new, bringing the total number of participating… Continue reading →

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C7 H10 O3 contest – Week #2 Results

Posted on September 20, 2008 by alan

The C7 H10 O3 contest continues with three new entries. The winning team nearly hit the jackpot: 140 references. Congratulations Orissa and Rachel !!The other teams submitted molecules that looked pretty interesting to me, but I guess organic chemists haven't… Continue reading →

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Mnemonic = memory aid

Posted on September 19, 2008 by alan

Several years ago I came across a Chem 201 exam with the following written in the margin: "Albert is sick and in pain, so I brought clean forks". Afterward I asked the student what that was all about and she… Continue reading →

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