You can create gold out of lead, as well as theoretically any element out of any other element, but it's not really chemistry at that point. You'd need a particle accelerator and it only works in atomically small amounts. So anyone saying they "mix some fluids together to create gold" is still an idiot, not necessarily due to their way of describing the procedure, but because they don't understand one of the most basic aspects of chemistry.
I think, like in all things, that there's a nuance to be had. If we're talking about the main character of a story and his defining characteristic is that he's a chemist, the writer better have some pretty in-depth knowledge of chemistry, otherwise his characterisation will probably be pretty unconvincing. If we're talking about The Smart Guy of a Five Man Band, you've got more leeway, because there's plenty of other things going on beside the genius being clever, and the reader probably didn't come to read a lecture about chemistry. If we're talking about a standalone story instead of a roleplay, it also means the genius in question probably isn't the PoV character, which makes a difference.
I'd say that unless the character's scientific field is the focus of the story, you don't need to have quite as much knowledge on the subject as your character supposedly does. You just need to have enough to avoid Dunning-Kruger syndrome (thinking you know all about it because your knowledge is so lacking that you don't know what you're missing) and not make a fool out of yourself in front of someone who is actually an expert.
As long as you can give a surface-level description of what your character is doing, you can be pretty convincing. Writing "Science Guy creates some mustard gas to throw at Those Damn Nazis" is lame because he might as well be using magic to conjure it. But adding a little extra detail goes a long way, e.g. "Science Guy enters his lab, grabs some chemicals from his storage, and begins synthesising mustard gas. Soon he will have enough to repel Those Damn Nazis." This is still very basic, but it gives somewhat of a practical indication of what he's doing. I don't know the exact method for synthesising a haloalkane, but I understand the concept of synthesis well enough to know that I'm not making a fool of myself by describing something blatantly impossible (i.e. synthesising gold). If you're diligent you can say that he's using ethylene gas and sulphur dichloride to synthesise it, but it depends on your audience whether or not that adds anything. Even if you know it's accurate, to most it might as well be technobabble.
I'm terrible at examples, but the point is that the level of technical detail you give is a matter of style. I don't think a lack of in-depth explanation is inherently bad, as long as there is enough explanation to be able to visualise the character's actions, and to be able to tell that the character isn't magically pulling things out of his ass. It should be mentioned that I would personally enjoy receiving greater depth than the example I gave above, but that doesn't mean it's inherently a poor way of doing it, depending on the circumstances.
