Oh stereochemistry...

I am and am not a visual person. I like doodles, I like seeing pictures, and I like quick sketches of molecules in a mechanism. But I'm not a terribly spacial person, so converting from 2D to 3D in my head has never been the easiest thing in the world for me. I mean, I'm okay...there are most certainly people who are worse than me...and after practice, parts of chirality, ring-flipping, and eclipsed vs. staggered has become rather intuitive. But more often than not, when it gets complicated I'll pull out the old modelling kit or build it on Spartan.

I've been tutoring sophomore organic lately, and I'm great with explaining how to rationalize acidity and basicity, how to draw resonance structures, arrow pushing, and hybridization effects on geometry. I can make up those problems on the fly, no problem. But the one area I find really difficult to tutor is this really spacial stuff. Because to this day, I occasionally get tripped up when converting a wedge-and-dash diagram to a chair diagram, especially in fused-ring systems. And I don't really have a good systematic approach to it all; it's all a bunch of built up intuition, and when intuition fails, collapsing back on my model kit.

Now I think this has little to do with my abilities as a chemist. We buy model kits for a reason, and even my stunningly knowledgeable organic chemistry professor, Pat McDougal, on occasion uses a modelling kit--he says if it's really important (like for example, it was a compound he was making in his research lab) he doesn't trust his brain. I mean, I recognize the importance of stereochem and conformers but I wonder...is it really necessary to emphasize stereochemistry to the degree they do in first semester organic chemistry?

From what I can tell, assigning Cahn-Ingold R/S notation to carbons and converting Fischer projections in your head quickly is highly dependent just on whether you happen to be a spacial person. I was helping a kid out with this three-ring fused system that had wedge and dash drawings, and it asked you to convert those wedge and dash drawings into chair drawings, labeling axial and equatorial substituients, and hell I got tripped up on it. He told me it took three modelling kits to make that model.

On the one hand, I see how it's important to be tested on that material; it's like IUPAC naming compounds. I can't remember all the rules now and when I'm writing up data I tend to use ChemDraw's "convert structure to name" function, but I can read a reagent bottle and pretty much know what what I'm picking up looks like. I don't think I would have that same facility if at one point I didn't have to memorize all the rules. I don't think anyone would argue that one's ability to name organic compounds has anything to do with one's conceptual understanding of the material--on the other hand, it's an important skill to learn once. Likewise, being forced to really learn how to deal with looking at 2D structures of 3D molecules is important because it is an aspect of chemistry. And it is possible to teach yourself to get better; I've certainly gotten better with practice, so I don't mean to say that it's hopeless if it's not the sort of thing that you get easily.

I guess the problem I have with it is that a lot of people get freaked out that organic chemistry is too hard and isn't something they can do just because they aren't able to do that spacial stuff easily. And a lot of kids that don't have the work ethic to get to the meat and bones of organic chemistry, but just happen to be highly spacial people just "get" it right away and have one "gimme" test. I tell my tutees who struggle with it that stereochem and conformers are important to conceptually understand (I mean it comes up understanding inversion of stereocenters, how a reaction might be thermodynamically controlled, etc.) but if they are having a killer time with this stuff, and it's the sort of problem that they would get tripped up on in the time crunch setting of an exam, it's not what o-chem is all about (additionally I give them advice about what sort of molecules they should make before the exam to bring with them...oh how I've been saved by a pre-made chiral carbon). Success in organic chemistry in the long run is about building up reactivity profiles--and that's what draws people to the subject rather than "is this the R or S enatiomer".

The other thing I find hard to tutor is MO theory, but that's another story all together. One of my professors referred to hybrid orbitals as "chemistry's stork story" for "how does bonding occur?" I know enough hand wavy, descriptive mnemonics to get by, and I've accepted that. I mean, I just did a homework problem about metal-halogen exchanges at cyclopropane rings because "the more s-character, the more electronegative, so the carbanion is stabilized" and that's fine. Ahem...moving on to making things...