Yesterday I referred to the book Arrowsmith by Sinclair Lewis, wherein one of the characters (Prof. Gottlieb) makes disparaging remarks about organic chemistry. I have duplicated the full passage from Chapter 2 at the bottom of this post. Enjoy! (And here’s a link to the entire book. You can read it for Spring Break.)
The following models were optimized at EDF2/6-31G**. They include IR calculations (unscaled frequencies). Unfinished 4/8/15
- 1,2-H in acyclic carbocation: TS | Rct
- 1,5-H in acyclic system: TS | Rct
- 1,5-H in cyclic system: TS | Rct
- 1,7-H in acyclic system: TS | Rct
- 1,5-CH3 in acyclic system: TS | Rct
- 1,5-CH3 in cyclic system: TS | Rct
- 1,5-H vs CH3 in 5-methyl-1,3-cyclopentadiene: H TS | CH3 TS | Rct
- Claisen: TS | Rct | Pdt
- ortho-Claisen: TS | Rct | Pdt
- Cope: meso-3,4-dimethylhexa-1,5-diene: chair TS | boat TS | Rct | Pdt
Spartan can produce a number of “job failed” messages. The most frequent reason for failure is “maximum number of optimization cycles was reached.” I’ll explain what this message means, why it is so common, and what you can do about it.
Most papers that include molecular models publish the atomic coordinates and total energies in the supporting information. The list of coordinates can be easily downloaded, saved on your computer, and converted into a Spartan’14 model by following these steps:
The authors of paper #2 reported on the behavior of a chiral dienophile in Diels-Alder reactions. For reasons that I will discuss on another day, they wanted to conduct their reactions at the lowest possible temperature and so a Lewis acid catalyst was required. They investigated several catalysts based on B and Al compounds and this raised some questions during our discussion last Monday.
Today’s class presented two formalisms that organic chemists use for connecting rates, rate constants, and the shapes of PE surfaces:
- Arrhenius equation (old-school but still useful and still widely used; go here for more background on collisions & kinetics)
- transition state theory (more obvious connection to thermodynamic quantities, but web pages say this is not useful when barriers get very small)
I forget whether this question came up in our discussion of the Scholz paper (paper #1), but 2-norbonyl cation was crystallized with Al2Br7 anion. The authors described this anion as “weakly coordinating,”
Our interest in binding challenging ions such as the [CX3]+ (X = Cl, Br, or I) cations (35–37) to weakly coordinating anions (38, 39) led us to exploit the ability of soft bromoaluminate anions, such as [Al2Br7]–, to stabilize, for example, the [C(CH3)3]+ carbocation in the solid state (40).
The unusual properties of this anion leap out from a comparison of potential maps of Al2Br7 anion (left) with BF4 anion (right) (EDF2/6-31g* made with iSpartan). Potentials on the former map never get more negative than approx. -340 kJ/mol, while those on the latter reach much more negative values (the extreme occurs at -615 kJ/mol in the orange-red bands between F’s).
Welcome back to Reed. And thank you for signing up for Chem 324 – Adv. Physical Organic Chemistry.
You are probably wondering what this course will be about and that’s why you came here looking for some information. Well, your curiosity is well warranted. The course always changes a little (sometimes a lot!) from year to year. Perhaps because this year is the second time that I am offering the course in just two years, this enrollment is much smaller than last year’s crazy number and this will require some changes to fit the new enrollment.
This year I plan to follow the trails that have been laid down in recent years so don’t hesitate to talk to some seniors who have taken the class, but you can also expect some changes to fit the smaller class size and the better access you will have to molecular modeling software (more on that to come).
For now, take a look at what I have planned for this semester by looking at the About page.