S205 - The Molecular World

So, I'm part-way to a natural sciences degree with the Open University. My first course was S205 The Molecular World (well, really it was DSE212, but that was a few years ago and not with a view to my current degree). I like reading what other people thought of courses and the nitty-gritty of them from a student's perspective, so I thought I'd present my views on said course here. So that you know where this view point is coming from, my first degree was in maths and the last chemistry I did was at A-level around 10 years ago.

If you're interested, I've also written a brief post on some advice if you're starting this course.

Course Books and Content

Book 1 of the course is short and sweet (just over 20 pages) and basically acts as an introduction to/taster for the course the case studies (which I'll come back to later).

Book 2, Introducing The Molecular World (~70 pages) is an overview of some of the "bread and butter" chemical knowledge that you'd need throughout any chemistry course - the basics of atoms, chemical bonding and chemical/electronic structure, the periodic table and patterns in it, functional groups, molecular shape and reactivity. These are all set out at a fairly basic level, since each topic is taken into much greater detail in later books, but you need at least a grounding in them all to be able to really understand later material. How you get on with this depends on your background; if you've got a good chemical background (e.g. a recent A-level) you'd probably be able to skim through most of this effectively, but it would be understandable (with a little effort) for someone with little or no background in chemistry. Like I said, my last chemistry course was 10 years ago, so things were a bit hazy for me but I felt like this was a good, solid and fairly interesting start to the course.

Book 3, The Third Dimension comes in two parts - Crystals (~95 pages) and Molecular Shape (~50 pages). I found the part on crystals to be fairly dry, which was a bit off-putting so early in the course. A fair chunk of it was describing the characteristics of different crystal structures, which went in one ear and out the other; it struck me more as the sort of thing I'd have to memorize before the exam. That part starts with a general discussion of close-packed arrays of spheres and how this reflects the internal structure of metals before moving on to the structure of ionic solids, ionic radii in crystals, molecular crystals and defects in crystal structures.

I found the second part of book three much more interesting. It covers molecular shape including isomerism, chirality (molecules with mirror images that aren't identical) including molecules with many chiral centres and chiral centres in ring structures.

Book 4, Metals And Chemical Change (~190 pages), seems fairly thick, but a lot of it is a fairly gradual introduction to the core principles you actually need to remember - you can miss a good few chapters out of your revision, for example. It covers thermodynamics, why some reactions happen while others don't (and how to predict which ones will happen), the Born-Haber cycle and the extraction of metals from their ores. It finishes by applying these concepts specifically to group I and II metals.

Book 5, Chemical Kinetics and Mechanism is broken down into (obviously) Chemical Kinetics (~95 pages), The Mechanism of Substitution (~45 pages) and Elimination: Pathways and Products (~25 pages). Chemical kinetics links in nicely with both the previous book and the later parts of the book - instead of looking at whether a reaction will happen, it looks at how fast it will happen, what factors affect the speed of a reaction and how this information can be predicted from/used to suggest the mechanism of the reaction. This is probably the most maths-heavy part of the course, and some people found the maths here to be a little bit of a challenge - if you've got a good grasp of algebra and logarithms it's a breeze, otherwise make sure you understand the maths help that's provided and you'll be fine.

The second part of book 5 discusses substitution - one of the three major classes of organic reaction mechanism (the others being elimination and addition). It starts off with a general discussion of reaction mechanisms and how to draw/describe them using chemical notation before applying these principles directly to the two types of substitution mechanism, as well as what factors affect which mechanism will be preferred by a reaction.

The third part of book 5 is similar to the second part, only discussing a different type of mechanism and without the need for the general introduction to reaction mechanisms. This was nice; it was good to see material that was brief because you'd already learned the underlying principles.

Book 6, Molecular Modelling and Bonding (~100 pages) goes into details about the techniques used to predict what shapes molecules will adopt, moving on to quantum chemistry, symmetry, atomic and molecular orbitals (i.e. the shape of electron clouds) and how these affect molecular reactivity, and the bonding in metals and semiconductors. I found the section on how semiconductors work and semiconductor doping particularly interesting.

Book 7, Alkenes and Aromatics is broken down into Addition - Pathways and Products (~20 pages), Aromatic Compounds (~35 pages) and A First Look at Synthesis (~40 pages). The first part draws together the principles of reaction mechanisms from book 5 as well as the material on molecular orbitals from book 6 to look at the mechanism of the last of the major classes of organic reaction. Hence the brevity again - you should be familiar with the basic principles from the last two books, this book just squishes together in a fairly neat way to form a coherent whole.

The second part of book 7 discusses benzene, the basis of all aromatic compounds, including its orbital structure. It also looks at substitution reactions applied to benzene and how substituents affect these reactions. The final part is a precursor to book 10 - it looks at how synthetic routes (i.e. ways of synthesizing drugs and other chemicals) are planned, the issues involved, how to construct simple synthetic routes and how changes in existing ones will affect the outcome.

Book 8, Separation, Purification and Identification is broken down into Chemistry: A Practical Subject (~65 pages) and Spectroscopy. The first part covers methods for the separation and purification steps of this book's title. I found this section fairly dry and we were told before-hand that this section wouldn't be examined, so I didn't study it very in-depth.

The second part of book 8 is entirely taught via a computer program - revision notes were available on the course website though. It goes fairly in-depth into the theory behind both infrared and NMR spectroscopy before covering how to interpret both types of spectra for a wide range of organic compounds. The program was interactive, allowing you to try your hand at interpreting IR/NMR spectra, eventually using both together to determine the structure of some quite complex molecules. I enjoyed this part of the course as it was mainly about problem solving - applying a little bit of knowledge in sometimes fairly complicated ways.

Book 9, Elements of the p Block is a fairly beefy size (~205 pages) and covers acids and bases as well as hydrogen chemistry, but the bulk of the book is dedicated to patterns and trends in the p block (groups III-VIII, the largest block of the periodic table). I can't really comment too much on this book except that this was by far the least enjoyable part of the course for me - it reads a lot like a huge list of facts to remember, and felt like wading through xenon-infused treacle. In short: Not my cup of tea. I quickly decided I wanted little to do with this material, but this wasn't too much of a problem as the structure of exam meant that certain parts of the course can be skimmed over, if not totally skipped, (so long as you're prepared to do more work on certain other parts of the course) and book 9 was one of them. The upshot was that I read just enough to do the assignment question (though not very well...) on this book before ignoring it.

Book 10, Mechanism and Synthesis is the final and largest of the course books, and consists of Carbonyl Compounds (~40 pages), Synthetic Applications of Organometallic Compounds (~35 pages), Radical Reactions in Organic Synthesis (~40 pages), Strategy and Methodology in Organic Synthesis (~75 pages) and finally Synthesis and Biosynthesis: Terpenes and Steroids (~40 pages).

The first part discusses the chemistry of the carbonyl group (carbon double-bonded to oxygen), which has a number of uses in reaction synthesis. The second part describes how various organic compounds that include a metallic element can be used in synthesis, another important class of reactions. The third part discusses radical reactions, which involve a different type of bond separation than normally found, including chain reactions. Part four picks up where the last part of book 7 left off, covering approaches for planning more complex synthetic routes. I found this part very enjoyable as it brings together previous parts of the course to solve the sorts of problems found in synthesis. It soon became apparent that chemical synthesis at this level really is more of an art form than a science. The final part of the course covers the synthesis of some naturally occurring compounds.

Course Software

I found the software easy to use and helpful, though there was a fair bit to install and some of it was redundant - e.g. there were two chemical drawing programs to install, one an updated version of the other (though I didn't realize this until I'd installed them). The software for book 8 (spectroscopy) was easy to use, and I found the puzzle-solving in it quite fun.

However, I was running the course software under Windows XP - some people using Windows Vista or Windows 7 had issues installing and using the software, but so far as I know they seemed to get resolved in the end. The conference software for remote tutorials didn't work very well under Linux (the audio was very broken) but worked fine when I booted into XP.

Assignments and The Exam

The assignments were fairly challenging at times, but certainly doable if you cover the material well. The questions were nice and specific (some students have complained of vague, wishy-washy questions in other courses) and there were no essay/experiment write-up type questions (though I got the impression there were in previous presentations). In addition to 6 tutor-marked assignments there were also 2 interactive computer-marked assignments (i.e. you answer numerical/multiple choice questions on a web page). I found the computer assignments useful for jogging my memory; whereas the tutor-marked assignments were all about the recent topics we'd covered, the computerized ones covered the whole course up until that point, and so forced you to revisit earlier material. Some found this a pain, but I was glad for the chance to revise and consolidate everything so far.

I found the exam fairly easy to prepare for - there was an exam guide that laid out what sections would be covered. As I said before, this meant you could selectively ignore certain parts of the course - not an awful lot, and you needed a decent grasp on most of it. A certain amount of "question spotting" was possible, but not very much.

The exam itself consisted of four sections. The first constituted 40% of the marks and had 12 questions, though you only had to answer 8, which is a fairly generous amount of choice if you ask me. These questions could be taken from any part of the course, but weren't too in-depth. The remaining three sections each had three longer questions, but you only had to answer one from each section (i.e. three questions in total). These were each worth 20% of the total marks for the exam and so required much more detail but, as mentioned before, the organization allowed you to focus revision on a few subjects, within certain limitations.

I found the assignments and exam manageable - I ended up with a distinction overall, so I was pretty happy with that.

Overall

The course started out moderately paced - the workload picked up towards the end (roughly from book 6 onwards) but I never found it overbearing. I liked how the sections linked together and built upon each other in a nice, logical way (especially the organic chemistry).

There were case studies at the end of each book from book 3 onwards. They build on the material in the book but with a more specific "real life" application in mind (e.g. the chemistry of liquid crystals or high-temperature semiconductors). They're not required or assessed at any point - they're purely there for interest. While what I did read was interesting, I didn't have time to read much of them.

Overall, I found this course really interesting, even if there were a couple of sections that were a bit dull, and I feel I gained a lot from it.