[Reelin]

> I assume there are formulas to determine how substrates and reagents will react with each other?

Well there are things we've experimentally tested, and things we haven't. Most reactions fall into the latter, and we can only make educated guesses about them.

If we could analytically solve the Schrödinger equation (we can't), we could accurately predict outcomes under perfect reaction conditions.

> are there many reactions in organic chemistry that are completely unknown?

Yes, the vast majority. But bear in mind that we can make educated guesses based on patterns, so we're not completely clueless.