Chem 201 Archive – Alan Shusterman

Category: Exams

  • Day 0, 2019 – the things you need to do BEFORE your first class

    Welcome back to Reed. We have an exciting organic chemistry curriculum planned for the 2019-20 editions of Chem 201 and 202, and we will get off to a flying start so here goes…

    Reed’s first week of classes is short because Monday is Labor Day. This means that two Chem 201 sessions, the Monday afternoon lecture and the Monday evening lab lecture, cannot meet. And because the course schedule ties the Monday and Tuesday lectures together, the Tuesday, Sept. 3, morning lecture is cancelled too. Our first days (Day 1) of lecture will be Wednesday, Sept. 4, and Thursday, Sept. 5. Your attendance at your scheduled lecture section on Day 1 is absolutely required.

    The Labor Day holiday does not impact the lab schedule. Our first (Week 1) lab sessions will meet Tuesday-Friday, Sept. 3-6. Check the schedule for your lab day (Tu/W sections meet 1:10-5 pm, Th/F sections meet 12:30-4:20 pm) and show up in Rm. 209 at the scheduled time or maybe a few minutes earlier.

    What will you be doing in lecture and lab? What do you need to do before class and lab so that you are prepared? These are excellent questions and the following instructions will guide you. Note: the following instructions have already been sent to all registered 201 students by email. Read, review, act as your situation requires.

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  • Molecular Model Kits – Is NOW the time?

    The Day 3 materials offered a small taste of where we are headed next: the 3-D world of molecules. Carbon is tetrahedral.

    Does this wedge-dashed diagram make sense? Can you rotate it in your head (rotate around any bond or any axis, rotate by any amount 90, 180, 240 degrees)? Can you the rotated figure? Can you reflect it through a plane of symmetry? Can you rotate and reflect and draw? One carbon is just the beginning, my friends!

    Model kits are really valuable learning and thinking aids. What is more, I permit you to use models on quizzes and the final exam! (see Exams policies) If you would like to purchase a molecular model kit, I highly recommend the kit shown on the left. You can buy it at the Chemistry stockroom. $20. Cash. Or buy a (slightly, gently used and well-kept) kit from a former o chem student.

  • Drop-In Tutors for Finals

    The DoJo will have drop-in tutoring available 7-9 PM for Chem 201 on Sat (12/10) and Mon (12/12).

    Sam and Alan will also be in their offices for drop-in-consultation for much of Th/F/M/Tu/W, weather permitting.

  • Challenge/Conference Problems or HW/Book Problems

    I have (and will) post some extra “challenge” problems from time to time. Let me explain their purpose so that you can work these problems into your schedule in an appropriate way.

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  • Quiz #1 Statistics etc

    69 students took Quiz #1 in-class last week and 59 students turned in take-home quizzes. Here are some statistics on how the class performed:

    • 40-50 points. 13 students scored in this range on the in-class quiz. After considering take-home results, this number rose to 23 students.
    • 30-39.5 points. 33 students scored in this range on the in-class quiz. After considering the take-home results, this number fell to 31 students (more students rose out of this group via the take-home than entered from below).
    • 20-29.5 points. 18 students scored in this range on the in-class quiz. After considering the take-home results, this number fell to just 12 students.
    • 10-19.5 points. 5 students scored in this range on the in-class quiz. After considering the take-home results, this number fell to just 3 students.

    As you can see, the take-home quiz appears to have given many students a boost (in fact, only 16 of 59 scored noticeably worse on the take-home quiz; see below). This data should strongly encourage anyone who wants to improve their understanding of the material (as well as their scores) to attempt the take-home quizzes.

    I also took a closer look at how students performed on the take-home and how this affected student scores. (more…)

  • Get ready for Quiz #1 (& Advice from 2013)

    As you prepare for our quiz later this week, keep two things in mind:

    1. There are lots of resources to help you: sample quiz (with answers) from 2013, practice problems online and in your book, online supplements that I have written, me, helpers in the DoJo.
    2. In order to benefit from these resources, you have to allow time for them to operate. Very few challenges can be turned around instantaneously. The “computer” that you call your brain is based on living, growing cells and the chemical reactions they undergo. You are not silicon-based.

    For some quick inspiration, check out Advice from 2013’s Chem 201 class (part 1). Also, make sure to acquaint yourself with the guidelines for taking in-class and take-home quizzes on our Exams page.

     

  • Exam 5 results

    Two weeks ago I offered my perspectives on exam scores (Some data …, Dec 1, 2013). Since then another exam has been completed and I can provide you with the latest results:

    • Exam 1 – 44 (80-100%), 17 (60-80%), 3 (below 60%), median = 42
    • Exam 2 – 40 (80-100%), 17 (60-80%), 7 (below 60%), median = 42
    • Exam 3 – 9 (80-100%), 25 (60-80%), 30 (below 60%), median = 30
    • Exam 4 – 14 (80-100%), 20 (60-80%), 30 (below 60%), median = 31
    • Exam 5 – 32 (80-100%), 22 (60-80%), 11 (below 60%), median = 39.5

    These figures may differ a bit from data provided earlier in the semester because the current figures are based on the 65 students who are still enrolled in the class (we started with 71 in lecture).

    As you can see, exam scores have followed the historical pattern: a slight drop from #1 to #2, a large drop from #2 to #3, and increases from #3 to #4 to #5. Of course, these statements apply only to the class as a whole; individual scores may have followed a very different pattern. Nevertheless, this pattern supports two claims that I made at the start of the semester:

    • organic chemistry “catches most students by surprise” at some point, and
    • nearly everyone eventually figures out a successful strategy for learning with this material

     

  • Some data (and advice) on exams…

    This will sound a bit odd, but we have barely reached the middle of the semester. Obviously, I’m not referring to the calendar — the final exam is just over two weeks away — but if you count exam points, you might see what I’m driving at. So far there have been four short exams totaling 200 points. What remains are another short exam and the final exam totaling 250 points. So slightly over half of the ‘exam’ semester is still waiting.*

    (*Actually way more than half for some students because of the Exam Rescue policy which allows the final exam score to also replace two short exam scores.)

    This post discusses two important exam-related topics. First, it provides statistics on the scores for Exams 1-4. Second, it tells you how to assess your exam scores. Unfortunately, the section on exam assessment is fairly generic — I can’t discuss the scores of any individuals — so I urge everyone who has concerns and/or questions about their work in Chem 201 to come see me in person.

    My door is open.

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  • Some tips for Exam 3

    As you prepare for Exam 3, make sure that you learn to quickly identify the roles that different molecules might play in a chemical reaction. The sooner you can decide that a molecule is probably an acid (or base, nucleophile, electrophile, solvent), and that certain atoms in the molecule are proton donors (or proton acceptors, electron donors, electron acceptors, or leaving groups), the sooner you can move on to solving the problem.

    Lists of acidic functional groups have been provided, but how efficiently can you recognize basic functional groups? How about nucleophiles? (Sorrell Tables 6.2 & 6.3) Or aprotic and protic solvents? (Sorrell Figure 6.7) Sorrell’s chapters often end with a useful Reaction Summary (see p. 233-4). Here’s a link to a summary that I handed out to students in 2012. A tip for the future: as you study (this means work an activity, read the book, …), you should build your own summary of ‘things to know’. It isn’t enough to answer a couple of questions that illustrate a principle like primary RX react with Nu faster than secondary RX. You need to summarize this principle for yourself.

    Mitsunobu Reaction. I didn’t say much about this reaction in class because I ran out of time, but you need to know the reaction (i.e., know how to ‘predict-plan-explain‘) for the next exam. You don’t need to know all of the subtleties of its mechanism, however. Just focus on these 3 points: What is the nucleophilic substitution step, SN1 or SN2? What is the ionization state of the Nu? What is the leaving group? There is considerable disagreement about the details of the mechanism, e.g., the steps leading to the formation of an OPPh3 leaving group. If you’re interested, compare Sorrell’s (poorly drawn) mechanism with alternative (and more plausible) mechanisms presented in Wikipedia and at the Organic Chemistry Portal.

  • Exam #1 – getting ready & what to expect

    The first short exam will be in-class Tue-Wed (Sept 17-18). It will run about 25 minutes. The brevity of the exam can make the experience feel a little intense so here are a few notes on how to prepare and what to expect:

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