(first published Aug 20, 2008)
My first genuine taste of organic chemistry came in my sophomore year of college (73-74). I studied from a large (1000 page) textbook not too different from yours. There was a lot to remember, but I was doing alright until the second quarter when a subtle and unannounced change in the book quite threw me.
My first genuine taste of organic chemistry came in my sophomore year of college (73-74). I studied from a large (1000 page) textbook not too different from yours. There was a lot to remember, but I was doing alright until the second quarter when a subtle and unannounced change in the book quite threw me.
This "change" appeared when we began studying the chemical reactions of
alkenes, our first "reaction" chapter. I had read the entire chapter
and I had not had any trouble following the formulas and explanations,
yet I was completely stymied by the end-of-chapter problems. I looked
at one problem after another, but I couldn't find even one that I could
answer. I couldn't even start an answer (and going back to look at the
chapter, something that I hated doing, didn't help one bit). I don't
recall what went through my head, but I felt profoundly incompetent
because, just a week earlier, I had been doing very well.
In those days we didn't have solution manuals so I decided to walk across campus to find the lab where the TA who ran my weekly problem session, a graduate student, was working on his doctoral research. Being a nice guy, but perhaps also because he was surprised that any of his 16-odd students had actually found his dingy third-floor lab, he was more than willing to help. We found a well-used chalkboard in one corner of the lab and he talked me through a couple of the "what reagent will turn A into B?" and "what do you get when you combine A and B?" questions that had been stumping me. After about 20 or 30 minutes, I realized I was starting to get the hang of it, but that I didn't have any of the background information I needed to work these problems on my own. I would need to reread the entire chapter. More importantly, I would need to read it differently this time because, even though the words and formulas had gone into my head, nothing had stuck. I couldn't look at a problem and say, "oh yeah, I remember seeing something just like that." So, I headed back to my room, sat down with my book and a pencil and started to reread the chapter, writing and drawing formulas as I went. My problems didn't magically vanish. In fact, "studying" o chem had just gotten a lot harder and more time-consuming, but for a while, at least, I wasn't stuck and I knew where to go for help the next time.
The o chem lab was another interesting place. My first assignment was to convert benzene, a smelly liquid, into benzophenone, a crunchy white crystalline solid. I don't recall being given much advance information beyond two pages of instructions that contained many words I didn't understand ("reflux"? "rotovap"?), warnings that scared the begeezus out of me ("benzene is a cumulative liver poison"), and a drawing of an impressive-looking apparatus. I was clearly lost, but it didn't occur to me to go find a TA, so I decided that when I got to lab I would look for someone who looked like they knew what they were doing and I would copy everything they did.
My Follow-the-Leader strategy worked fairly well for about two hours, at which point a (different) TA came along, looked at my apparatus, and said, "you can stop that and work it up." I was happy to stop, but when I looked around the lab, I discovered to my consternation that everyone else was still boiling their reaction mixtures. I was going to have to go it alone. Since I still couldn't make heads-or-tails of the remaining instructions, I decided the only practical option was to slow waaaay down, give my lab mates a chance to catch up, and then play Follow-the-Leader again. In fact, I only needed to fiddle around for about 10 minutes before they had caught up and everything started rolling along smoothly again until I reached the last step: evaporating the solvent from my product. Instead of being left with a white solid residue like everyone else (this was actually the point at which I learned that benzophenone was a white solid), I was left with a colorless liquid. I showed the liquid to the TA, who remarked, "oh, your product oiled out" (apparently my "liquid" was now an "oil") and went on, "let me get you a seed crystal." I stood there puzzled, but patient, holding the flask that contained the liquid/oil until he returned with a small vial containing white crystals and a spatula. He carefully transferred one or two tiny crystals from his vial to my "oil", whereupon the entire mass instantly solidified. He smiled and said, "there you go" and I was relieved that this sudden amazing transformation had solved all my problems, for a week anyway.
In those days we didn't have solution manuals so I decided to walk across campus to find the lab where the TA who ran my weekly problem session, a graduate student, was working on his doctoral research. Being a nice guy, but perhaps also because he was surprised that any of his 16-odd students had actually found his dingy third-floor lab, he was more than willing to help. We found a well-used chalkboard in one corner of the lab and he talked me through a couple of the "what reagent will turn A into B?" and "what do you get when you combine A and B?" questions that had been stumping me. After about 20 or 30 minutes, I realized I was starting to get the hang of it, but that I didn't have any of the background information I needed to work these problems on my own. I would need to reread the entire chapter. More importantly, I would need to read it differently this time because, even though the words and formulas had gone into my head, nothing had stuck. I couldn't look at a problem and say, "oh yeah, I remember seeing something just like that." So, I headed back to my room, sat down with my book and a pencil and started to reread the chapter, writing and drawing formulas as I went. My problems didn't magically vanish. In fact, "studying" o chem had just gotten a lot harder and more time-consuming, but for a while, at least, I wasn't stuck and I knew where to go for help the next time.
The o chem lab was another interesting place. My first assignment was to convert benzene, a smelly liquid, into benzophenone, a crunchy white crystalline solid. I don't recall being given much advance information beyond two pages of instructions that contained many words I didn't understand ("reflux"? "rotovap"?), warnings that scared the begeezus out of me ("benzene is a cumulative liver poison"), and a drawing of an impressive-looking apparatus. I was clearly lost, but it didn't occur to me to go find a TA, so I decided that when I got to lab I would look for someone who looked like they knew what they were doing and I would copy everything they did.
My Follow-the-Leader strategy worked fairly well for about two hours, at which point a (different) TA came along, looked at my apparatus, and said, "you can stop that and work it up." I was happy to stop, but when I looked around the lab, I discovered to my consternation that everyone else was still boiling their reaction mixtures. I was going to have to go it alone. Since I still couldn't make heads-or-tails of the remaining instructions, I decided the only practical option was to slow waaaay down, give my lab mates a chance to catch up, and then play Follow-the-Leader again. In fact, I only needed to fiddle around for about 10 minutes before they had caught up and everything started rolling along smoothly again until I reached the last step: evaporating the solvent from my product. Instead of being left with a white solid residue like everyone else (this was actually the point at which I learned that benzophenone was a white solid), I was left with a colorless liquid. I showed the liquid to the TA, who remarked, "oh, your product oiled out" (apparently my "liquid" was now an "oil") and went on, "let me get you a seed crystal." I stood there puzzled, but patient, holding the flask that contained the liquid/oil until he returned with a small vial containing white crystals and a spatula. He carefully transferred one or two tiny crystals from his vial to my "oil", whereupon the entire mass instantly solidified. He smiled and said, "there you go" and I was relieved that this sudden amazing transformation had solved all my problems, for a week anyway.
That sounds like an interesting reaction. Does it follow the same principles that occur when a supersaturated solution of NaOAc is seeded or mechanically agitated causing the liquid to rapidly crystallize?
The phenomena (rapid crystallization) are similar, but the principles are slightly different. My oil was not really "supersaturated". It was more or less pure and solvent-free, but it couldn't reach its equilibrium (crystalline) state without some help.