I recently had one of these frustrating episodes. In my Organic Chemistry class we have been covering substitution and elimination.
***disclaimer: To any non-chemists out there, much of this may not make sense. I'm not going to try to explain what I'm talking about, because based on the response of my students, I'd fail miserably.***
I put the following reactions on the board:
Many of you will recognize this as a classic question posed to organic chemistry students since Alexander first described his ether synthesis. One route will work quite nicely as written, but the other route is fraught with failure. Do you know which is which? If you've read this far, I'm sure you do.Route A will work. Route B, however, will fail to make the desired product because elimination (to form 2-methylpropene) will predominate.
I put both reactions on the board and asked my students which one will work and which one won't.
Dead silence.
I rephrase the questions to something like, "one of these is a valid strategy and one is not. Which one will work and which one will fail to make the ether?"
More dead silence.
I start asking leading questions, but nothing is clicking. I finally get annoyed and ask, "how many carbons do you need to form a double bond?"
A student timidly answers, "2?" I say, "exactly. Which reaction will undergo successful substitution?"
Nothing.
It went on like this for about 15 minutes. I could not get them to realize that in route A, elimination is impossible. Or, if they did, they could not explain it to me.
This has really annoyed me, because if the entire class fails to figure something out, the most likely culprit is me. Besides, the example I describe above is NOT a difficult concept. I spent about half of a class period describing the difference between the two.
I'll find our tomorrow if it worked. This is the first question on tomorrow's exam.
UPDATE: Only 20% of my students got the answer correct. The others chose B. This is preposterageous!!! They will learn.
9 comments:
Oh, I see, you are still sacrificing virgins to the pagan god Gnawluge. Good luck with that.
Whenever I get the "Labrador Retriever Look" (fixed pleasent smile, vacant stare with head slightly tilted) I just keep on plowing. The way I figure it the optimum "teachable moment" died in a snowbank about ten minutes ago and everyone is on auto pilot. So I make sure that everyone is taking notes, get the material covered and make a note to myself to go over it again from another direction in tutorial.
In my opinion, once they go Labrador on you you are ditching your lecture in the Hudson so just get them ready for the cold water of mid-terms.
I wouldn't kick yourself over it not sinking in with everyone. There would be a lot of times when I knew the answer in class, but didn't feel like answering, so I just sat there as dumb as the rest of my peers. I suspect that might have happened.
If you heat reaction A up, you might get some elimination, so there, smoke that, Mr. Teacher Man.
The point is, don't get too bent out of shape over it. It might have just been one of those days when part of the class was like "Eff it all. When's the beer getting served?"
I think they were probably so scared shitless of not knowing the right answer that they didn't dare give any answer at all. I felt that way a lot during OChem second semester... Panic just shuts brain cells down.
AHH yes, the "big blank look". I have seen it many times this year. Even though the kids in my classes are usually too stoned to focus and that is why they have been staring intently at the chalk board & not at what I have written.
Plus I have to admit, I have done my fair share of the Big Blank back in my college chem days.
I have to agree with Liberal Arts Chem. (And I am going to plagiarize the hell out of that Labrador term!!!) Some times they just have to plow through the small stuff to get to the big stuff before everything sinks in. Sort of a reverse learning process that seems to work.
Deer-in-the-headlights is the expression my graduate student called it. Labrador Retriever Look is good but does not the complete bewilderment of students when they do not understand.
If it is any comfort my general chem students seem to have forgotten how to convert from hours to seconds. I think they were scared of the fact that the answer was in microseconds.
After dealing with a bunch of high schoolers during a chemistry event at a local Science Olympiad, I'm willing to say "maybe it's the students".
I *am* impressed that you're willing to consider that it might be your fault. Speaks well of you.
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