As I understand organic chemistry there is no simple generalization that allows us to predict reaction outcomes- rather we transform molecules using a sequence of known reactions.
This has me wondering how these known reactions came to be known. My first guess would be that the structure was empirically observed before and after the reaction. If this is the case what instrumentation would be used to observe this?
If not, how else were these reactions determined and if they were not all developed by trial and error, what is the name of the branch of chemistry that deals with hypothesizing them?