Today I’ll share with you one thing about organic chemistry that made me feel really, really dumb when I took it. And looking back, I didn’t need to. So if it helps at least one person feel less dumb, that’s a win for me.
When I first took ochem, I was well-accustomed to the style of teaching used for math and physics, where instructors often went to the trouble of deriving equations on a board to explain where they came from before pummelling us with them. If it was difficult, it was only difficult because I wasn’t grasping the logic. That’s OK: I at least understood where I was getting things wrong and had faith that things actually made sense.
When I took ochem, the instructor showed us new reactions – addition of OsO4 to alkenes, say – but never told us WHY or HOW it came to be that these reagents “work”. No explanation. It felt to me like these reagents were being pulled out of a magic hat.
Every time we learned about a new reagent, I’d ask myself, “How did it get decided that OsO4 [for example] is the best reagent for dihydroxylation? Why OsO4 and not, say, RuO4 (which is, after all, one row up the periodic table)? Or, “why palladium (Pd) in the hydrogenation of alkenes and not some other metal?”
It all seemed so arbitrary at the time, and it drove me bonkers. I felt dumb because I thought that I was just “supposed” to know from first principles how and why these reagents did their magic, and my instructor probably thought I was dumb for not knowing this either. I thought I was missing something obvious, and felt ashamed for it.
Many, many years later I realized that my instructor, even if he was the most brilliant person in the world, could not have predicted from first principles that these reagents do what they did was he in my position. That’s because a great deal any of the things we learn in organic chemistry are the results of discoveries, not deduction. For instance, H.C. Brown, winner of the 1979 Nobel Prize for his application of the hydroboration reaction, discovered it by accident [note 1] not by some sudden flash of insight. Only once he’d discovered the reaction did he assign an army of graduate students and postdoctoral fellows to explore every facet of the reaction in more detail.
Our knowledge of organic chemistry is hard-won from experiment. The reagents you see thrown up on the chalkboard – AlCl3, BH3, LiAlH4 are the tips of icebergs. You only see the finished result: “BH3 is used for the hydroboration of alkenes”. What you don’t see is the accidents or serendipity that led to its discovery and all the man-years of effort in learning about the reaction in more detail and optimizing the process. You also don’t see all the time spent going down blind alleys exploring reagents that don’t work as well for this process. “It just works”. That’s why it all seems magical.
The bottom line is this: you’re probably not as dumb as you think. The course moves really fast, and there isn’t time to go into all the little corners. There are reasons for why these reagents are used, and how they work particularly well, but the tools to fully understand them don’t come until later on in a chemical education (and sometimes the best answer is merely, “we use this reagent because it’s convenient and cheap!”). And some questions you might scold yourself for thinking as “dumb” – like why OsO4 works so well for dihydroxylation, but RuO4 does not - lead you down interesting paths. Hold on to these questions for later. Chemistry is still a living science. We don’t know everything yet, there are many more experiments left to do.
[Note 1] – Actually Brown’s postdoc Dr. B.C. Subba Rao discovered the hydroboration reaction, not Brown himself. From his Nobel Lecture:
In the course of these studies of selective reductions, a minor anomaly resulted in the discovery of hydroboration. My coworker, Dr. B. C. Subba Rao, was examining the reducing characteristics of sodium borohydride in diglyme catalyzed by aluminum chloride. He observed that the reduction of ethyl oleate under our standard conditions, 4 moles of hydride per mole of compound, one hour at 25”, took up 2.37 equivalents of hydride per mole of ester. This contrasted with a value of 2.00 for ethyl stearate. Investigation soon established that the reagent was adding an H-B, bond to the carbon-carbon double bond to form the corresponding organoborane.