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6.9 How to Approach Synthesis Problems
We have seen many reactions in this chapter.
In order to solve synthesis problems, you need to have all of the reactions at your fingertips.
We saw a few ways to make aldehydes in the beginning of the chapter.
You are in trouble if you don't.
At times organic chemistry can get difficult.
It's not enough to be a master of mechanisms.
It builds an excellent foundation for understanding the material, and that is an excellent start.
At the end of the day, you have to be able to solve synthesis problems as well.
All of the reactions must be organized in your mind in order to do that.
Two ways to oxidize and an ozonolysis were used to make ketones and aldehydes.
We saw how hydrazones could be used to reduce the amount of ketones in the air.
We moved on to three different types of carbon nucleophiles--Grignard reagents, phosphorus ylides, and sulfur ylides.
We looked at the Baeyer-villiger oxidation's utility for synthesis.
That is all we saw in this chapter.
In the last part of the chapter, we will solve synthesis problems.
To claim that you have them at your fingertips, you need to know these reactions well.
Try to achieve that goal by doing the following.
If you can, take a separate piece of paper and write down all of the reactions listed in the paragraph above.
You need to make sure that you can draw all of the products.
You are not ready to start thinking about problems if you can't synthesis.
Students don't know how to approach synthesis problems.
The student's poor study habits are usually the reason for the difficulty.
There are synthesis problems that you can do.
You will get frustrated if you try to run before you learn how to walk.
There are too many students making this mistake.
Take my advice and focus on the individual reactions.
Try to fill out a blank sheet of paper with everything we have done in this chapter.
If you have to look back into the chapter to get the exact reagents, that's fine.
Don't think that you are ready for synthesis problems once you have filled out the sheet, it is part of the studying process.
You can't be ready until you fill out the entire sheet of paper and don't look back.
Continue filling out a new sheet until you can do it all without looking back.
You should get to a point where you don't need to look at the summary that we just gave.
If you can reconstruct the summary in your head, you should be able to write a list of all the reactions.
It sounds like a lot of work.
It will take some time.
You will be in a good position to tackle synthesis problems when you are done.
If you are frustrated with synthesis problems, don't complain if you get lazy and skip this advice.
It would be your fault if you tried to run before walking.
If you get to the point where you have all of the reactions at your fingertips, then you can try to prove it by doing some simple problems.
We will be able to conquer multistep synthesis problems once we have all of the reactions down cold.
The product is an enamine, so we will need a nitrogen nucleophile.
We need to decide what kind of nitrogen is in it.
We will need a secondary amine since our product is an enamine.
We need to decide if there are any special conditions.
There are special conditions for the reaction between a ketone and a secondary amine.
We need acid-catalysis and Dean-Stark conditions.
If you get stuck on a few problems, it might be helpful for you to fill them out again in the future.
The problems are not listed in the order in which they appear.
If you were comfortable with the problems, you should be able to solve them.
This transformation is more involved than the previous problems because it can't be done in one step.
While maintaining the presence of the carbonyl group, we need to install an ethyl group.
We have a two-step synthesis to accomplish this transformation.
There is a point to be made about synthesis problems.
The product is an enamine if we focus on it.
There is only one way to make an enamine.
We need to find a way to convert the starting compound into a ketone.
An oxidation reaction can be used to convert alcohol into a ketone.
The last problem was easy because it had a two-step solution.
That is beyond the scope of the course.
You won't have to deal with more than three to five steps.
It is possible to become a master of solving synthesis problems with a lot of practice.
It all depends on how well you know the reactions.
There is rarely only one answer to a synthesis problem, as you work through the following problems.
There are many correct ways to achieve a transformation as we learn more.
Don't think that you have to find the answer.
You may be able to come up with a perfectly acceptable answer that no one else in the class would think of.
The most exciting moments are those.
When you solve synthesis problems, there is room for creativity.
Suggest an efficient synthesis for each problem.
There could be more than one correct answer for each problem.
Do not be discouraged if you propose an answer that does not match the answer in the back of the book.
It is possible that your answer is also correct.
Most of the reactions you need to know were covered.
The goal of this chapter was not to cover everything.
We wanted to lay a foundation for you when you read your textbook and lecture notes.
We saw that there were similarities between mechanisms and that there was a simple way of categorizing them.
You can look through your textbook and lecture notes for the reactions that we didn't cover in this chapter.
With the foundation we have built in this chapter, you should be in good shape to fill in the gaps and study more efficiently.
Make sure to do all of the problems in your textbook.
There are more synthesis problems there.
The more you practice, the better.
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