Have you ever tried to get a group of picky eaters to agree on one place to go to dinner? Maybe you have a friend who’s vegan, one who’s vegetarian, another who’s gluten free. Maybe you even have a paleo friend that’s dating someone on a keto diet. How the hell are you supposed to find one place where they can all sit down and enjoy a meal?
This is what it sometimes feels like trying to set up a chemical reaction in the lab. I may have a set of molecules that I know will get along swimmingly and make something amazing if I can only get them to mix together in the right solution. This means they all have to dissolve in the same liquid medium, which is a challenge when each molecule has its own solubility preferences.
See, the key to chemistry is getting all of your molecules to interact with exactly the right energy in exactly the right orientation. That means they have to be mixed evenly in a solution that lets them move around. They have to mingle. If you brought all of your friends to a restaurant and had them all facing the same way, it would be really hard to get a conversation going amongst the whole group. Instead, everyone has to be able to see each other if you want them to talk. It’s the same with getting molecules dissolved in the same solution.
For example, I have a reaction that I’ve been working on that gave me a lot of problems at first. Material 1 is soluble in solvent A, but not solvent B. Material 2 is the other way around. I ran my reaction in solvent A and then again in solvent B, but I didn’t get very much of my desired product in either case. So instead, I tried running the reaction in a solution of 30% A in 70% B, and BAM! Product! (Of course, by BAM! I don’t mean anything other than I let the solution sit and stir overnight and worked it up the next day, but it really was very exciting to see that it worked.)
So in chemistry as in dinner dates, you have to make sure that all the key players can interact with each other if you want anything worthwhile to happen.