Using Flash Cards to Learn Reactions
As we begin to accumulate a large number of reactions, which must be learned in both directions, developing a system for keeping track of the reactions becomes crucially important. I strongly recommend the use of flash cards.
Write the starting organic compound and the reagents on one side:
and the product(s) on the other side:
- Use a specific molecule: no R groups or unattached bonds, because one of the things you will be working on is recognizing functional groups as the significant part of a molecule.
- You will not be attempting to memorize the reaction, but rather to practice thinking about the kind of molecule and the kinds of reactions you know it to undergo, or the reactions you know that produce it.
Where do you get the information that goes on the cards? Should you use the specific reactions that I present in class?
Making the cards is a "learning experience".
When you have a collection of cards, stack them reactant side up next to some blank sheets of paper.
- Look at the first card.
- Ask yourself, "What kind of molecule is this?"
- Having identified the functional group(s), then ask yourself, "What reactions do I know for this functional group?"
- Then try to match the reagents shown with those for the reactions you know: B2H6 for hydroboration, for example.
- Recall the special features of the reaction: for example, hydroboration has anti-Markovnikov regioselectivity and syn-stereoselectivity.
- Finally, WRITE the anticipated product structure on the blank paper.
- Move on to the next card, and repeat the process.
- When you are finished, flip the cards over and check your answers.
- For any that are wrong, try to decide what you missed.
- Did you confuse two reagents?
- Did you miss the stereoselectivity?
Shuffle the cards before you use them again!
The next time you study reactions, stack the cards product side up, again next to some blank paper.
- Look at the product, and ask yourself, "What kind of molecule is this?"
- "What reactions do I know that produce this kind of molecule?"
- Now your clues about what reaction to select must come from stereochemistry observed in the product, regioselectivity observed, and so on.
- For example, if the product shown is a specific stereoisomer of an alcohol, that signals hydroboration, which is our only stereospecific preparation of alcohols (and will remain so all year).
- WRITE on your paper what the reactant and reaagents were that produced that product.
- Again, check your work only when you are completely finished, and for each error, think about why you made it.
If a particular card becomes so familiar that you think you know automatically what is on the other side of it, make a replacement for that card. We are NOT using the cards to memorize, although that will happen to some extent. We are using them to develop habits of thought.
Although I have illustrated flash cards using organic reactions, they can be made for other types of problems as well; for example, a molecule on one side and an isomer on the other.
Another useful study technique is making a reaction catalog.
Spending a little time categorizing reactions as answers to these questions will pay dividends.
- This can be a small-sized loose-leaf notebook or a second collection of flash cards.
- The idea is to organize reactions by what they accomplish: making carbon-carbon bonds, preparing particular functional groups, controlling stereochemistry, and so on.
- The reaction catalog is an aid to learning retrosynthesis.
- In tackling a synthetic problem, we ask ourselves, "What kind of molecule is this?"
- "What are the ways I know for making this kind of molecule?"
Again, making the catalog is as important as using it. Write the reactions "backwards", just as you will in solving synthetic problems. Choose real examples, and be sure to note any special features of each reaction. Many reactions will end up in several categories.
If you construct the catalog like the flash cards, with product on one side and reactant on the other, you can use the individual pages or cards just like your flash cards.
The emphasis on WRITING answers is what makes this active studying, as opposed to highlighting things in the text, which is totally passive. Writing forces the ideas to reside for at least a moment in your brain, which improves the chance that they will stick.
This page last modified 3:09 PM on Monday August 18th, 2014.
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