Archive for the ‘Organic’ Category

My Design for Organic Exams

Tuesday, October 21st, 2014

ed_academic_bigIt’s fall semester at SLU, and I’m teaching organic chemistry for our majors once again. Last year, I was focused on just getting through the course. I was so consumed by producing slides, homework assignments, practice exams, and real exams on a tight schedule that I didn’t get to think hard about the finer points of design until the class was over. Now, on the second pass, I can focus on making improvements rather than creating everything from scratch.

At SLU, instructors don’t get assigned TAs for proctoring and grading unless the class has greater than 30 students. In the spring, the majors’ class fell below this number and I had to think about designing exams to make grading as efficient as possible without eroding their effectiveness as tools for teaching and thoughtful evaluation. The system I settled on was different from my experience in both college and grad school, so I thought I’d share.

I’ve settled into a system in which quizzes and exams generally have four or five sections/problems picked from the following varieties: multiple choice, mechanism, synthesis, A+B reactions, explanations, and calculations. While I’ve never been a huge fan of multiple choice, it allows me to test a variety of straightforward points without the strain of having to grade a wide assortment of free-response questions. My multiple-choice questions are typically five choices, with students getting +5 points for a correct response and +2 points for leaving a question intentionally blank. This scoring system introduces a penalty for guessing; students need to recognize that sometimes the best option in life is to admit “I don’t know.”

In my system, if there is an exam on Wednesday, the students have a quiz due on the previous Friday that covers the same material. Each quiz contributes 2% to the final grade in the course, while each exam contributes 20%. The quiz has the same length, format, and answer sheet as the exam, except the problems are harder to compensate for the fact that I give students 48 hours for the quiz and allow them to talk with each other about the answers. I like how this approach requires the class to be familiar with the exam material almost a full week before the exam, and that students have an incentive to form study groups and debate answers to hard problems. I never learned as much in organic chemistry as when I was trying to defend my proposed answers to classmates. Finally, having what is essentially a hard practice exam due on the Friday before the “real” exam means that I can return it graded and marked with comments by Monday. In many cases, these quizzes serve as wake-up calls to students while there is still time to fix issues that need attention.

In every chemistry class I’ve taken, students either wrote their exam answers directly on the problem booklet or in small blue exam books. I find these response media are murder to grade because you spend so much time flipping through pages, hunting for answers, and flipping back to write the subtotal for that problem on the cover page. And, of course, there are always two or three students who get creative and write their answers out of order or on the back side of pages.

To solve this problem, I started writing exams such that students have to place all of their answers on a single letter-sized piece of paper. I draft an answer sheet for each exam on which it is clear where each answer should be written. When the answer is a single word or structure, I’ll typically draw a box for it. The use of a single sheet minimizes the burden of flipping, while the answer boxes (located at the same spot for every student) minimize the burden of hunting. Here’s a sample answer sheet typical of one of my orgo exams:

sample_exam_answer_sheet

I copy answer sheets onto 65-lb. card stock so that both sides of the sheet can be used without the pen ink bleeding through to the other side. I find that the smooth sheets sold under the Neenah brand are better than sheets of the less expensive Staples brand, which have an annoying coarse texture on one side. The card stock also gives a regal quality to the answer sheets. These puppies are suitable for framing and will withstand decades of wear if pinned to the refrigerator door of a proud parent.

Another nice thing about having students limit their answers to a single sheet is that the entire stack for the class can be scanned without hassle. Most modern office copiers are capable of sheet-feed scanning, so if your exams have no staples, you can scan the entire stack of paper all at once and e-mail the data to yourself as a single PDF. What a wonderful miracle of technology.

I scan the entire set of answer sheets both before and after I’ve graded them. In doing so, I have a permanent record of performance that I can access for eternity. If there is an issue over improper grading or a student attempting to cheat by altering answers upon return of the graded copy, I can refer to the electronic file. If a student needs a letter of recommendation two years down the road, I can open up the file and make specific comments about his/her performance. And if I want to mine data in the future for some pedagogical purpose or project, all of the data will be available for analysis.

A final important feature of each answer sheet is that I have a line for students to write their names at the top of the back side. This makes returning exams very simple, because I can fan them in columns in alphabetical order on a table and have students come in groups to pick them up. With only the top inch of the back page of each sheet exposed, students cannot see each other’s grades. Of course, as the columns thin out, I adjust the sheets to prevent greater exposure.

As I discussed before, I allow students to bring handwritten notes into exams. They serve to emphasize that organic chemistry is about analysis—not memorization. Also, having students organize the information of each unit onto a single sheet of paper forces them to make connections about the material in their minds ahead of the exam. This semester, I’ve started collecting, scanning, and returning these note sheets as well. I am fascinated at how students organize their thoughts, and I plan to use this information in my future letters of recommendation when appropriate. How an individual organizes her thoughts on paper gives you an interesting window into her mind.

So, that’s the system. Are there drawbacks? Yes. I tend not to write long mechanisms or synthesis problems that go over four steps, because there isn’t enough space to do so. With that said, I’m not sure if these problems offer much added benefit relative to alternatives with more concise answers.

One thing that I’ve found surprising is that even though the answers for the exam all fit on one page, there are students who still feel they need three hours to finish. I thought that offering four shorter exams instead of three longer ones would make time a non-factor, but often at the end of two hours, I still find myself nagging for all of the papers to be turned in.

Anyway, I like how this system works and will continue to modify it to work better for both the students and me. It is ironic that as a teacher, I feel that I am the one in the classroom who has the most to learn.

The Pauper Professor’s Orgo Library

Wednesday, December 11th, 2013

chembarkfc_kit_200Well, it looks like I’ve been ignoring the blog again. Sorry about that.

We are in finals week here at SLU, and the end-of-the-semester crunch has definitely crunched me (with a lot of help from lab stuff, two chemistry “business” trips within the last month, and the fact that I will be getting married in two weeks (!).

I’m teaching Organic 1 this semester, and it has consumed an inordinate amount of time. But the experience has also been a lot of fun and a good training ground for figuring out how to run a class efficiently.

Like many orgo teachers, I began the year by insisting to the students that the best way to do well in the class is to work practice problems (and lots of them). When I was a wee lad taking orgo at NYU, I walked uptown to the fantastic Barnes & Noble at 5th and 18th and bought copies of Vollhardt and Streitwieser to supplement the problems in Jones. My weekly routine was to read through the Jones chapter in two nights while also making index cards that cataloged each reaction along the way. The rest of my week would be spent doing all the problems in Jones, then as many in Streitwieser and Vollhardt as I could stomach.

But textbooks aren’t cheap, and I feel icky about asking students to shell out extra money for supplemental problems after they’ve already forked over $260 (!) for the class’s required textbook. Of course, the used-book market is flooded with cheap, old editions of organic textbooks.

Over the course of this semester, I undertook a mini-project that involved scouring half.com for deals and assembling a small library of textbooks and solutions manuals as a resource for my sophomore organic students. The last volume arrived two weeks ago, and now my collection occupies almost an entire bookshelf in my office:

cheap_orgo_textbook_library

There are 16 books there: 8 sets of texts and solutions manuals. Here’s what I paid for each book + manual:

Bruice: $3.43 + $0.75
Carey: $3.26 + $0.75
Heathcock/Kosower/Streitwieser: $1.05 + $1.18
Jones: $0.75 + $0.75
Loudon: $4.07 +$4.12
Smith: $0.00 + $0.00 (this is the one SLU uses)
Vollhardt/Schore: $1.05 + $0.75
Wade: $2.22 + $0.75

Those costs are steals compared to the prices listed on Amazon. The shipping on each item ranged from $1.89 to $3.99 and was always more than the cost of each book. In total, my little collection set me back $74.14. The plan for next semester is to cart them over to the main library where they can be kept on short-circulation reserve. Students can check out the books for a day at a time—long enough to work or copy the problems in a chapter, but not long enough to hog the resource. Anyway, with eight texts as options, I’m hoping the market for orgo practice problems at SLU is now saturated. I should never again hear wailing about there not being enough practice problems available.

Anyway, the final exam for my class is this Friday—the 13th. I expect the only students who will encounter bad luck are those who haven’t been working enough practice problems.

Organic Chemistry Exam Show-and-Tell

Wednesday, November 13th, 2013

ChemBark's Orgo BunnyWhen I was in college, there was a professor who was notorious among the grad students for stopping them to show off his organic chemistry exam questions. Unlucky TAs on their way to the bog would get tied up for what seemed like hours going through drafts of exams in the hallway.

But now I think I know how he felt. There’s a certain degree of satisfaction associated with writing a problem that makes students integrate their knowledge of multiple subjects within a given set of consecutive chapters in whatever textbook you’re using.

Instead of stopping TAs in the hallway at work, I figured I could move the practice into the 21st century by using the blog. I’ll post any gems I’m proud of in this thread. Feel free to share your favorites as well.

To start…

Exam 1, Problem 3-2. (8 points) Draw the most (Brønsted–Lowry) acidic, optically-active isomer of C6H10.

Click here for the answer. The chapters for this exam included acids and bases, isomerism, functional groups, alkanes, and stereochemistry.

BRSM is Coming to America

Tuesday, May 28th, 2013

There’s a chemblog carnival afoot to wish BRSM well on his upcoming postdoc in the U.S. @JessTheChemist is curating the posts on her blog, here. You can check out more info on Twitter with the hashtag #BRSMBlogParty.

BRSM is a synthetic organic chemist with a great blog dedicated to the subject. I know little else about BRSM beyond that he/she is currently based in the UK. (Obviously, I’m not even 100% sure about his/her gender.) That makes answering some of the carnival questions harder, but I’ll give it a shot anyway:

1. What is your message for BRSM?

Best wishes for your upcoming postdoc in the US, wherever it may be and in whatever area of research.

2. What is one postdoc survival tip you would give to BRSM?

Try to be nice to—or at least respectful of—your colleagues. Be especially nice to people like janitors, security guards, secretaries, instrument staff, and administrators. There will be times where you’ll need their help getting out of a bind, and having any of these people as enemies can make your life hell.

3. Do you have a fun story you could share from your postdoc and/or US academic experience?

Well, there was the kitty job interview. There was also the time we (unknowingly) named our high-school science outreach program after a sexual act. Oops.

4. A survival tip for living in the US?

Relative to what you have in the UK, our public transportation is poor. If you are going to live in or near New York City, Boston, or San Francisco, you probably do not want a car—parking stinks. If you are going to live somewhere else, you probably do want a car.

5. What would you like to see on BRSM blog in the future?

Tasteful nude photos.

No, seriously, whatever you want. I would rather you keep blogging about what interests you than burn out blogging about what interests other people. And thanks for posting the Felkin-Ahn slides; I think they make a nice companion to Dave Evans’ Chem 206 notes.

6. Anything else?

Nope. Safe travels!

Jean-Luc Picard Failed Orgo

Monday, April 29th, 2013

Yes, you read that title correctly: Jean-Luc Picard, the greatest starship captain of all-time, failed organic chemistry at Starfleet Academy. In his defense, it was probably less to do with intelligence and more to do with being distracted:

I pulled that video clip so I can show it to my students during our opening lecture. It should go well with the “How to Win Orgo” handout.

Update (5/1): Thanks to a tip in the comments from “bad wolf”, I went and pulled a clip from Star Trek: Generations where it is revealed that one of Picard’s ancestors won the Nobel Prize in Chemistry. It makes his failure in orgo all the more astonishing.

WWWTP? – Markovnikov Edition

Tuesday, April 16th, 2013

Perfectionists take note: even titans of catalysis make embarrassing mistakes with their chemistry. Just look at this little oopsie that was caught by an astute reader in the Midwest.

It seems like there might be a bit of confusion hanging over the chemists developing methods for anti-Markovnikov hydroamination of alkenes at the Center for Enabling New Technologies Through Catalysis (CENTC):

centc_markovnikov_error

Ummm….yeah….that’s not the difference between Markovnikov and anti-Markovnikov addition.

Those of you who’ve taken sophomore organic chemistry will remember that Markovnikov’s rule states that protic functional groups (e.g., H-NR’R’) will typically add to double bonds such that the hydrogen adds to the less substituted carbon (and the other group, e.g., -NR’R’, adds to the more substituted carbon.) What Hartwig and coworkers have drawn as the Markovnikov product is still anti-Markovnikov. The products they’ve drawn might charitably be called conformational isomers, but they’ve failed to note any 3-D structure.

Of course, the true Markovnikov product would place the amine on the same carbon as the R group.