The Purpose of Trick Problems
Commenter Matt—one of several, it’s not this Matt—got his knickers in a twist about the last set of trick orgo problems that I posted. His rant is copied below.
I think this is sad, or at least the satisfaction that you can “get” students with them is sad. Look, if you paid some martial artist to teach you said art, and all that person did was throw you to the ground and beat the #$@$ out of you, then flex over you as if they’d proved something…you’d be upset. And they would be idiots for thinking there was any glory in beating the crap out of the unskilled and ignorant.
This is the academic equivalent of that. Again, not the hard questions, the smugness that so few can answer them.
If you, with years of experience, can’t fool even bright students seeing the material for the first time, you really are in sad shape. I’ve had professors and known professors who think like that, who somehow get their jollies by keeping score against their students. Psychiatric counseling is needed there.
The challenge is to so capture students with why the material is interesting, and so fascinate them with its intricacies, that you manage to move large numbers of them to the point where they CAN answer questions like these. Any utter imbecile can teach nothing and fool the whole class; it takes enormous talent and work to stimulate and teach people to where hard questions become easy. C.f. Feynman’s lectures in physics.
Matt needs to chill. Does he really think that I throw trick problems at students just for sadistic self-gratification? No. These types of problems are designed to serve a purpose, and the evil tone is facetious for the sake of entertainment. Let’s lighten up, people.
How about we run through some of the benefits of trick problems?
1. Trick problems call attention to fundamental concepts, usually in a memorable way.
2. Trick problems discourage students from going through the motions without thinking — A good trick problem can put the brakes on students’ running through problems on autopilot.
3. Trick problems can light a fire under your students’ asses — If students are flubbing problems, especially on something like a practice test, it’s going to motivate them to straighten up.
4. Trick problems keep your best students enagaged — As a teacher, you generally have to aim your lectures at the meaty part of the bell curve. Trick problems can provide a nice challenge to your best students to keep things interesting for them.
5. Trick problems raise your students’ expectations of exam difficulty — So much of students’ satisfaction with your teaching boils down to expectation. If students are only exposed to straightforward questions in their books and problem sets, many will get upset if they see any sort of curveball on an exam. But, if you present some really wicked problems in lecture or recitation section, they become conditioned to torture and learn to cope. Correspondingly, they will be grateful when they see straightforward or only mildly tricky problems on exams. Somewhat counterintuitively, trick problems (when used correctly) will ultimately help, not hurt, your teaching evaluations.
To compensate for the severe dullness of this post, here’s a blast from the past (a 2006 post on the old blog). Predict the products of the reactions below. Assume one equivalent of Grignard reagent relative to the starting material.
.
.
Answers after the jump…
.
Lessons: a) Don’t forget the acidic workup, b) Watch out for acidic hydrogens—they’ll quench your reagent, c) The initial product from the reaction of an ester and Grignard reagent, a ketone, is more reactive than the starting ester.
October 21st, 2010 at 2:31 AM
I always thought that it was silly to emphasize the acidic workup after Grignard syntheses since students typically don’t learn about workups for most other reactions. For instance, after a Fischer esterification, you’d neutralize the acid. Reactions with chromic acid in acetone are quenched with excess isopropyl alcohol. Diazomethane esterifications are quenched with acetic acid to destroy any excess reagent. Excess bromine or iodine can be destroyed by washing with aqueous sodium thiosulfate. And so on. It’s one thing to mention that Grignard reactions or metal hydride reductions are worked up with aqueous acid, but why emphasize it so much?
October 21st, 2010 at 7:16 AM
This reminds me of a time when I co-TA’ed o. chem with a below-average grad student. I made a quiz for my students: one question asked what happened when you mixed an aldehyde with excess methanol under acidic conditions, another asked what happened under the same conditions using a carboxylic acid.
The other TA didn’t bother consulting me for the answer key (of course, as a TA he shouldn’t have needed to, but this guy should have) and I happened to see the answers he gave to his students (he was dumb enough to have posted it on the course webpage). Sure enough, he had fallen into the trap I expected the undergrad students would and simply replaced the carbonyl of the acid with two methoxy groups.
October 21st, 2010 at 7:57 AM
In most of the workups you mention, nothing happens to the product of interest – workup makes the product isolable, but doesn’t actually do anything chemically to the product. Hence, when you draw a Jones oxidation, but don’t mention the workup, you haven’t affected anything you’ve drawn in the mechanism. Once you know the mechanism, you can account for the workup pretty easily.
Since much of the point of this set of problems is to follow the protons and to know their acidity, the emphasis on accounting for the alcohol proton doesn’t seem misplaced.
October 21st, 2010 at 1:21 PM
I would see them as instructive provided a good explanation of the answers are given.
This reminds me of a problem from my PChem thermodynamics final of undergrad, although I am unsure of its relevance to the topic. There was a boiling point elevation problem requiring the equation for non-ideal solution (where the constant must be derived). The problem was given with a boiling point in Fahrenheit and an elevation change in miles. It was a huge curveball in an already difficult exam. I don’t know the exact results, but I’m certain no one in the class got full credit on it. Afterwards, students asked the professor why he gave a problem with no SI units without warning, and he said that he expected us to know all units and constants. We think he just wanted to show us how difficult a test he could make. We were not happy about his reasoning, and a third of the students failed at the final. For many, this meant having to retake PChem the next year since the series was offered only once per year. The professor later went on to do other shenanigans and did not return the next year.
October 21st, 2010 at 2:38 PM
I think you tricked yourself. I would say in the first example, methyl gringard will deprotonate the alpha proton of acetophenone as the major product. Same thing for example 3 which will give you deprotonated acetophenone as the minor product. That’s why they invented cerium reagents. And if you can get one to work your a better chemist then me.
October 21st, 2010 at 3:29 PM
I think cerium reagents are very useful but sometimes they are overhyped. I’ve met chemists who look at that acetophenone reaction and give a knee-jerk response that cerium MUST be used because Grignards and organolithiums are just too darn basic. It’s kinda similar to when people overreact to broken glass.
I’ve reacted many tetralones and indanones with hindered Grignard reagents, and things have been just fine w/o cerium.
October 21st, 2010 at 3:35 PM
I think the best thing about a trick question is that when you finally figure it out you will never forget it, because it was such a challenge to figure it out in the first place
October 21st, 2010 at 3:43 PM
It’s always important to remember that your glassware needs to be dry for these reactions. I recommend heating your flask using a Bunsen burner to a high temperature for a period of 30 min (until Na+ is emitted from the glass surface, giving the blue gas flame a yellow color). CAUTION: Overheating or maintaining this temperature for extended periods may cause the flask to melt or implode! Use of a blast shield is recommended.
October 21st, 2010 at 4:15 PM
Uh, really? I mean, yeah, an hour or so in the 110°C oven sure, but 30 min with a Bunsen burner for a Grignard? (Am I irony-impaired here?)
October 21st, 2010 at 6:21 PM
@Dan: Check out this paper.
For the reaction of acetophenone with CH3MgI, the addition of a methyl group is favored over the enolization (deprotonation) reaction by 40:1. I can’t imagine that switching to CH3MgBr would completely reverse this preference. Incidentally, the enolization is preferred when you start loading up the benzene ring with methyl groups.
If you wish to offer an apology, I will graciously accept one.
October 21st, 2010 at 6:43 PM
Incidentally, ANYONE ELSE WANT ANOTHER PIECE OF THIS?! Matt? Dan? Wolfie? Royce?
This blog is supposed to increase my knowledge, not my levels of testosterone and stress.
October 22nd, 2010 at 7:40 AM
@Paul … with Viggo Mortensen lurking in the background, I think that we’re all a little hesitant.
Unfortunately, for me, all organic problems are trick problems. FAIL.
Also, I gave a test today to my gen chem class where I asked an economics question (albeit relative to the problem they were given). We’ll see how it turns out.
October 22nd, 2010 at 9:41 AM
Writing an exam is tricky business. For my organic class I usually shoot for 50% of the question being those that could be answered if you showed up for class everyday, read most of the text, and did most of the assigned homework i.e. memory work and regurgitation. 40% of the questions are at the next level i.e. do you really understand the principles behind all that stuff you learned? 10% of the questions are designed to challenge the best students i.e. can you apply what you’ve learned to something new that you may have never seen or considered or can you synthesize multiple concepts together that may have been initially thought to be unrelated? This seems to work out well for my classes and I usually have exam averages around 70%.
I know some who take great pride in having exam averages at 50% or below. I’m not sure I get this. Anyone could write an exam that blows students away. It would be very simple to do and is not related to how smart the professor is. I am absolutely positive that a social work professor at my university could write an exam that I would fail. Does that mean that they have superior intellect? I am sure that a janitor could write an exam on proper floor waxing technique that I would fail. Same question…
Exams are designed to evaluate whether the class is actually learning the material you are teaching. If the majority of the students do poorly on an exam it is a always reflection of some combination of a) that the professor is a poor teacher b) that the students are not preparing and c) that the exam material is inappropriate. If you usually consider b as the problem, make sure that you are looking at a and c too.
At any rate, the questions that Paul wrote in this blog post are my bread and butter for those 40% type questions. The test if students are not just memorizing, but understanding.
October 22nd, 2010 at 9:55 AM
A. hole, I will send you some good seminal papers on floor waxing if you are still struggling in your class.
Best,
Viggo
October 22nd, 2010 at 10:13 AM
I’m imagining Paul stalking around the arena with his Gladius Hispaniensis, yelling “ARE YOU NOT EDUCATED?!?!?”
October 22nd, 2010 at 12:44 PM
Trick problems are great, IF you prepare them to think that way. If the first time they see a trick question is on an exam and they all get it wrong, it’s the teacher’s fault for not teaching them how to think about problems in a broader context in a manner conducive to overcoming the “trick.”
October 22nd, 2010 at 8:06 PM
Paul – why not comment on this – : http://onlinelibrary.wiley.com/doi/10.1002/anie.201004704/abstract
See third page, next to last paragraph. Copper does nothing.
Sly way to avoid a retraction from Science. Only Science would let you republish a Friedel Crafts without doing a simple control study.
Looks like the textbooks on Electrophilic aromatic substitution don’t need to be changed after all… See these news articles (of many on the topic): http://www.rsc.org/chemistryworld/News/2009/March/19030902.asp and http://pubs.acs.org/cen/news/87/i12/8712notw1.html
What an embarrasment for cambridge. Papers like these are what is wrong with modern methodology.
October 22nd, 2010 at 9:58 PM
How dare you talk like that, striker! This is a group of mostly white chemists from England, not some obscure Chinese group. They clearly knew what they’re doing.
/how do you out-troll a troll? racism.
October 23rd, 2010 at 3:28 PM
my grandmother, 2 weeks before she died, said : wolfie, you make yourself unhappy doing these things
—
nonsense, Exicmer, you have to ignore the trick questions and remind yourself that all Chemistry Professors are crazy, one way, or the other
(Harvard Komma)
—
anyone among you guys knowing this ?
The Court Jester – The Pellet With The Poison ??????
http://www.youtube.com/watch?v=LS75NtlH3gI
—
I once sat in a cinema in NYC, in a film about the US war crimes in Japan. The lady next to me says, after my sighs “it is only a movie”.
Glory to you all who can distinguish what is right and what is not.
—
This is the black fox, and still playing the fool…
—
mace and chain
—
no, i cannot sly a man whose only crime was not to love too wisely, but too well
—
and take your helmet
—
where are the drinks ? one of them is poisoned
—
alright, Sir Griswald, prePare for a dye from Dow or BASF
we give up
—
Ed. note: Wolfie’s comment diarrhea has been condensed into a single turd.
October 25th, 2010 at 12:28 AM
That 70-80-90 degree temperature result sounds… iffy. So they run a control at 70 degrees and got no yield, why run controls at higher temperature as well? There is something that is not said here. I bet there was some yield at 70 degrees or something strange happened. I don’t trust this Scheme 4 completely. Still, at least they reported that copper is not a potential catalyst, which is nice. Of course this makes me loath to go through the earlier report (I missed it when it came out since it was in Science…).
Speaking of stuff, I recently had some iffy results in my catalysis that were too good to be true and the boss wanted to publish it. I’ve never had ‘that much’ luck with relationships, chemistry, etc… so I gave the reactions to someone else in the group (didn’t tell them what it was, just asked them to do it and run an MS) and they proved that I’m a fuck-up. Good thing that I’m suspicious of myself.
October 27th, 2010 at 2:47 PM
no, no, you have to state you are alive
I d’ declare you winner of this combat, if…
you were are better person
_____
the vessel with the pestle has the brew that is true
NO wonder Ertl’s is looking down on you.
_____
to the castle, please, before Nuzzo or any person from Penn State University ask me more, for example, why noone has ever explained that water would mix with oil
_____
Eugene, the true GMW would have said : they are …..
_____
and I protect my student PJB
_____
turd ?? = you don’t mean It, do you ?? it took me a while
October 27th, 2010 at 6:20 PM
wolfie: if you keep posting 3+ consecutive comments of incoherent crap, you’re going to get banned.
Get a notepad, write your brilliant thoughts down, and when they’ve reached critical mass, put all of them in a single comment.
October 31st, 2010 at 3:44 PM
If I were a professor of chemistry (which, as it appears, I will never come to be), I tried to challenge my students. If it appeared that they are not the necessary assholes for this job, I’d choose another one.
October 31st, 2010 at 3:46 PM
not enough, yet ?
October 31st, 2010 at 5:03 PM
If I ever were to post anything in this post in a completely rational fashion
it would not be friendly at all. Be careful, my friends, I’ll tell you things you will not like.
October 31st, 2010 at 8:31 PM
Wolfie is suspended from making comments for one week.