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Putting Diels-Alder Products in Perspective

One of the things I like about teaching is that it helps me realize some of the things I take for granted that newcomers find difficult. The other night I got this question.

How do you know to draw the Diels Alder product this way?

I’ve gotten so used to thinking of molecules in 3D that I’d forgotten that this could be confusing. The starting materials are drawn from a top view, while the product is drawn from the side. Why was it drawn this way?

Think of it this way. Why did the owner of this 1978 Ford Pinto (yours now for $4550, if you act fast) depict their prized vehicle this way?

It’s a choice. There’s no one right or wrong way to show the car. He used the one that he thought gave the best view of it. He could have alternatively shown a picture of it from the front or the top. It’s still the same car,  although a rear view might not be the best choice, which might remind buyers of the Pinto’s notorious sensitivity to backside attack.

Like cars and cats, molecules are 3-dimensional objects and looking at them from different angles gives different perspectives of their structures. It would have been equally valid to draw it like this:

This is probably an eaiser way to visualize the molecule when you’re just getting the hang of these types of products, since everything is consistently from the top view.  The side view (at the very top)  just gives a slightly better perspective of the molecule in 3D.

If you make a model, this becomes a lot more clear.

As you get more comfortable with organic chemistry hopefuly you’ll have an easier time thinking of molecules as 3-dimensional objects. As long as your drawing shows all the substituents in their proper places, however, it’s really your choice of which style to depict your molecules in.

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