7.7 Synthesis Problems

7.7 Synthesis Problems

There are a lot of reactions in this chapter.

The majority of them involved the conversion of one carboxylic acid derivative into another.

You can make a carboxylic acid derivative from any other derivative that is more reactive.

We can't go directly from an amide to an ester because they are less reactive.

One important strategy to keep in mind is the proposal of a synthesis.

In this chapter, we looked at the chemistry of carboxylic acid derivatives, and in the previous chapter, we looked at the chemistry of ketones/aldehydes.

We have seen ways to convert from one realm to another.

It is possible to cross over from the realm of carboxylic acids into the realm of ketones and aldehydes.

Some textbooks and instructors will teach you a reagent that can convert acid to aldehyde in a single step.

Many hydride reagents are able to convert an acid halide into an aldehyde without attacking the carbonyl group a second time.
If you have covered aselective hydride nucleophile, you should look through your textbook and lecture notes.

You can always use the two-step method if you haven't already.

We have seen a way to do this.

We now have reactions that allow us to cross over from one realm to the other.

It might be difficult to see how this can be accomplished.

Thought and planning are required for synthesis problems.

You always want to go backwards as much as possible.
Let's work our way backwards.

The problem can be thought of as a "cross-over" problem with this one important step.

We need to cross over from the realm of carboxylic acids into the realm of ketones.

One reaction allowed us to do that.
We can use a cuprate to make a ketone.

In order to complete the synthesis, we need to convert the carboxylic acid into an acid halide, and we can do that with thionyl chloride.

Let's practice with some more cross-over problems.

It can be hard to identify the following problems as cross-over problems, but hopefully you will see some trends as you solve these problems.

If you are familiar with the ways that we have crossed over, you will be able to solve these problems.

You should notice that all four reactions have one thing in common.

Reduction-oxidation reactions are what they are.
The oxidation state of carboxylic acid derivatives is different than that of ketones and aldehydes.

Don't do the problems when you only have 5 minutes to study because you will need some time to do them.

When you sit down to work on these problems, make sure you have some time to spare.

For each of the following transformations, propose an efficient synthesis.

Try to determine which cross-over reaction to use in each case.

If your answer is different from the one in the back of the book, you should not conclude that your answer is wrong.

The goal of this chapter is to lay a foundation that will allow you to study your textbook and lecture notes more efficiently.

There are a few simple rules that govern all of the mechanisms in this chapter.

You can look through your textbook and lecture notes for those 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.