“To infinitive” VS “coordinating conjunction”

Question

Can you please help clarify my uncertainties regarding the use of to infinitive and coordinating conjunctions in each of the examples below? I like to know when we should use one over the other. Are there any rules or something I should look for?

1. I took the psychology class to acquire basic understanding TO understand more about human behaviors.

2. I took the psychology class to acquire basic understanding AND understand more about human behaviors. Which one sounds correct?

When would you use "to infinitive" over coordinating conjunction like "And" in this case?

Answer 1

There is difference in meaning, a major one.

I took the psychology class {to acquire basic understanding [TO understand more about human behaviors.]}

It basically means that you took the psychology class for the purpose of acquiring basic understanding. And this basic understanding was attained in order to understand more about human behaviors.

So: To acquire basic understanding in order to understand more about human behaviors, I took the psychology class.

I took the psychology class to {acquire basic understanding AND understand more about human behaviors}.

This one means that your purpose of taking the psychology class was to both acquire basic understanding and understand more about human behaviors at the same time, not acquiring basic understanding first and then being able to understand more about human behaviors. Both gains resulted from taking the psychology class only, not being able to understand more about human behaviors from acquiring basic understanding.

So: In order to both to acquire basic understanding understand more about human behaviors,I took the psychology class.

Both of them are grammatically correct, but the meanings differ.