If you look at organic chemistry like a language course, the first five or six weeks focus on giving you the alphabet and learning how the words are formed. But now, things are going to start going fast, because we’re going to take all those “words” and start putting them together into meaningful sentences. In other words, “grammar”.
Up until now, organic chemistry has focused on structure. You’ve learned about bonding, isomers, conformations, and stereocenters. The only reactions you’ve done (besides some free radicals, possibly) have been acid-base reactions.
Just like only certain combinations of words “work” in English, only certain combinations of molecules, when combined together, will change their bonding. These events are called “reactions”, and there will be a few major patterns to learn.
That’s right: the focus of the next half of the course will be on reactions. And it will require a whole different mindset than the first half did. Things are going to move pretty fast.
- Every reaction you will learn involves a change in bonding. Because electrons are the currency of chemistry, and every reaction is a transaction of electrons between atoms, my best advice to you when you learn a new reaction is to first pay attention to one thing: what bonds are formed, and what bonds are broken.
- You will also notice that reactions change the charge on different atoms. So we’ll devote time to going over the factors that stabilize (and destabilize) charge on molecules, because this is going to be key for understanding why certain reactions happen and others don’t.
- Next, learn how to draw the curved arrows for each reaction, since this is the accounting system that will tell us what bonds are broken/formed and also how the charges change.
- Also, the stereochemistry of the molecule will often change during a reaction. This is probably the most testable facet of learning a new reaction. Like I said earlier, stereochemistry is probably the most important theme of Org 1.
- Finally, if learning it all forwards isn’t enough, inverting the questions – thinking backwards – is the last, important step towards mastering a reaction.
One of the reasons why students tend to fall behind in organic chemistry is that they aren’t prepared for this point in the course where things start to change. So go back and make sure you understand stereochemistry, conformations, acidity/basicity, dipoles, bonding, and how to interpret line diagrams, because these are all going to come into play over the rest of the course.
So what can you do to prepare? One word of advice: look for patterns. That’s what the focus of these posts will be on, from this point forward. There’s actually a small number of patterns to learn. We’ll go through them, don’t worry.
Tomorrow, we’ll go through one of the key reactions in organic chemistry: substitution.
Thanks for reading! James