Course: CHM303
Instructor: Semmelhack
F 2014

Description of Course Goals and Curriculum

This course is designed as the first part of a three-semester sequence, CHM 303/304B and MOL 345 (biochemistry). CHM 303 will introduce the principles of organic chemistry, including the structures, properties, and reactivity of simpler organic compounds. The emphasis will be on the mechanisms of organic reactions, with examples taken from biology when appropriate to illustrate the principles. For a complete presentation of the subject, the course should be followed by CHM 304B in the spring.

CHM 303 lays the groundwork for the year-long sequence of organic chemistry (“orgo”), and is organized into three parts, each of which builds on the previous one(s). The first unit introduces concepts needed to go forward. The first section involves learning to name and draw compounds to become proficient in the “language” of orgo. Then, the basic properties and parameters of the named compounds and functional groups are introduced, including electronic effects (e.g. electronegativity differences), size of different groups (“sterics”), and resonance. Some of these concepts may relate to topics from CHM 201-2 or AP Chemistry, but overall orgo is very different from those classes and does not require much prior knowledge from them. The second unit covers methods of analyzing different spectral data. A common problem considered during this unit involves determining a molecule’s structure given its spectra; this occasionally uses concepts from the first unit. These two units have a relatively manageable pace, but the third unit picks up speed. This is where the meat of organic chemistry—reactions and all of their mechanisms—begins to be covered. Most of the problems here ask you to predict the result or write a mechanism for a reaction you haven’t seen before, considering reactions (unit 3) but also basic parameters (unit 1) and spectral data (unit 2). Each unit culminates in a two-hour exam (luckily, the lowest score of the three is dropped). The final exam leans heavily towards the third unit’s style, as does the second semester.

Since the course is highly cumulative and concepts build on each other, it is essential to know the early material. While you are usually not directly asked to name a compound with its formal name, being able to quickly put a structure to a name and draw can be very useful. You use the basic parameters, particularly resonance, throughout both semesters as you try to judge what will happen in a reaction. Having the basic concepts down also helps minimize being overwhelmed in the last third of CHM 303. Reading and reviewing the lecture notes is a good way to understand the basic ideas, while extra problems are definitely the best way to practice and prepare for exams. As the professors say, the lecture notes are the primary source of material, while the textbook is supplementary.

CHM 303 at Princeton tries to avoid unnecessary memorization. All exams are open-book and stress the ability to apply concepts to solve new problems. Therefore, instead of memorizing facts, it is most useful to take complete and organized notes so you know where to find everything come exam day. The best way to get better at exam problems is to do more exam problems, which are easily found in the numerous old practice exams posted on Blackboard.

Not much background knowledge is assumed beyond the that from the prerequisite CHM 201-202/AP Chem. As mentioned above, though, the material in orgo is very different from general chemistry. Some people in the class probably had a little past experience with orgo, but this does not make much of a difference. If anything, there was some implicit facility in laboratory skills that was expected. Some students find adapting to the fast-paced, efficiency-stressing environment of a Princeton lab challenging at first, especially since if it is their first lab experience not working directly with a partner.

Learning From Classroom Instruction

Lecture in CHM 303 is a little different than some other science classes. Professor Semmelhack posts partially completed lecture notes online before class and completes them by writing additional phrases and molecules on them during lecture. No need for notebooks or laptops—the lecture notes are all you need to write on, and sometimes the organic molecules are already drawn out for you. Though a preceptor often posts completed notes on Blackboard after class, it really is worth it to get up early twice a week for this 8:30 lecture. Semmelhack explains the course concepts well and you will learn more from writing your own notes, in addition to knowing where everything is for the open-book exams. A good night’s sleep before lecture is extremely helpful, especially come Thanksgiving and afterwards when concepts fly by more quickly in lecture.

For each unit, the professor will also list relevant chapters and problems in the textbook. These are completely optional. If you do have time to look at the text, much of the concepts are summarized nicely in the subsection headings. Especially in Unit 3 and second semester, pictures of reactions in the textbook can be helpful to look at. The suggested textbook problems could be helpful, but there are so many practice problems between precepts, problem sets, practice exams and optional review sessions that the text problems are not essential. The textbook is also a useful tool in the open book exams—bookmarking important tables or diagrams can help, and if all else fails with a problem, a quick check in the index is worth a shot at solving it.

Precept organization changed in Fall 2015, the year after I took the course. Now, there is a short period where the preceptor reviews concepts, and the rest of the time is devoted to problem-solving. These precepts are very important—they choose the most central, applicable or difficult parts of lecture to review and then offer practice problems on those concepts. If you’re unsure about a concept, take careful notes and don’t be afraid to ask them to clarify something. It’s their job and they are very good at it. Working in groups with the problems and asking questions may be helpful, as the alternate perspectives of your classmates and preceptors can be invaluable. A preceptor’s response may highlight a broader point or tip that can be applied to other problems.

Labs highlight some of the lecture concepts, but are also designed to introduce basic organic lab methods and situations. You cannot bring the official procedure into lab but instead are required to copy down the procedure steps into your lab notebook. Make sure you know what you have to do, as the lab is an efficiency-based environment. Students become quicker with experience, but asking questions about proper technique, ordering the sequence of procedures, and anything you may be confused about can be particularly helpful. Both the lab TA and Henry Gingrich (the lab instructor) are great at explaining how to perform lab tasks, as well as how to connect lab work to lecture concepts. Your fellow students are good resources, too. There are a couple graded “quality control checks” on lab products, so be sure to know when these are so you can be extra careful those days.

Henry gives a few optional Lab Review Sessions that go over concepts covered in lab reports. Very often the types of problems he does there directly relate to either the lab report or the corresponding exam (at the end of every exam, there is a lab-related question). Starring important takeaways and keeping these notes may be helpful when writing lab reports.

Learning For and From Assignments

Problem sets are weekly, and while not officially graded, they may be most useful if done on time. After precept, they are the next introduction to the types of problems one can draw from each week’s lecture material. It helps to have reviewed the lecture notes a bit beforehand and have them with you when you do the problems. If you turn them in on time, the preceptor will correct it, which is a great help. Note especially where you went wrong, and consider keeping a list of “tips, tricks and patterns’” you gain from corrections.

There are a few lab reports each semester, which take some time but are not overly involved. Many of the most difficult questions are conceptual, so asking questions in lab and going to Henry’s Lab Review Sessions may be especially useful. After unit 2, the lab reports begin to make heavy use of spectral analysis, so it is essential to be comfortable with drawing conclusions from that kind of data.

Most of the grades come from the exams: three 2-hour “midterm” exams at the end of each unit and a 3-hour final, all open-book. The instructors allow each student to drop their lowest midterm score, but note that most students find the third exam the hardest. As mentioned above, knowing where to find all your notes is extremely useful in tackling the open book exams. One study strategy may involve reviewing the lecture notes and creating a mini “table of contents” of sorts to show in what lectures and on what page(s) to find each big-picture concept a few nights before each exam. Some students put similar “study guide” references together, like a table summarizing all the unit 3 reactions or a sheet of “tips and tricks” on how to find a structure from spectral data. Sometimes these resources come out of the McGraw review sessions (see below). Most importantly, keeping past problem sets and exams, as well as lab reports and procedures for the exam’s lab question, may be very helpful.

One way to prepare for exams is to do practice exams, which students may take under simulated test-like conditions (i.e. with “study guides” made beforehand, keeping track of time, etc.). Going over the practice exams afterward may be as helpful for mastering the topics as doing the practice exams themselves. Answer keys with scoring are posted alongside past exams, so it helps to correct your exams and perhaps even score them. As with problem sets, note especially where you went wrong and consider keeping a log of tips and clarifications. Students should not feel like they have to take every practice exam they post, but most students find taking at least two seriously to be most useful.

As the front page of the exam says, “WRITE SOMETHING”-- partial credit can be very helpful in boosting the overall grade. Even just writing part of a reaction or describing what general kind of structure the problem is looking for will help. It is also beneficial to go over a midterm when it is handed back. On a practical level, you could find an opportunity for a re-grade. But like a problem set or practice exam, a corrected exam is a great opportunity to see what you did wrong. Investigating what the key did instead and adding those methods to your “tips and tricks” list may be especially helpful for future exams given the cumulative nature of the course.

External Resources

There are so many resources for orgo! The McGraw Review Sessions may be very helpful, led by a grad student one night a week. It is yet another opportunity to review class concepts and work through some problems with a teacher who will readily answer questions. There are also the typical McGraw resources like Study Halls and Individual Tutoring, which could be useful if you want to work in a group or get more peer help. Self-formed study groups can also be good for this class.

The course recommends you buy a modeling kit. While it is never essential, it can be very useful in unit 3 when orientation and spatial arrangements are covered. If it is hard for you to visualize a molecule in 3D (as it was sometimes for me), they are a good tool to have.

What Students Should Know About This Course For Purposes Of Course Selection

While some of the horror stories are definitely over-stated, orgo definitely takes some work. The weekly problem set load may not be heavy, but when an exam comes up (of which there are three, plus the final), there is a lot of preparation required. Because of this, it’s best to take orgo only if you have a compelling reason for it (if you think you might be pre-med or a CHM/MOL/CBE/EEB etc. major, or know the concepts will be useful in your future path). However, don’t be scared of it! It is well-taught, there are so many resources, and everyone is in the same boat.

Freshmen who place out of CHM 201-2 should feel welcome to take CHM 303 right away, if their schedule allows. According to Henry, freshmen actually do better on average than sophomores, and if you have to take it sometime anyway, it will free up future years.  

You will learn more about organic chemistry’s application to biology and life sciences, as well as some knowledge about chemical synthesis. You’ll also get so much better at problem-solving, and at the end of it all, you’ll be proud of all you’ve learned!

Organic Chemistry I: Biological Emphasis

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