Should brussel sprouts ever taste like chemicals?
Brussels sprouts are in the brassica family, so you can get that family of strong cabbagey/spicey/sulfurous flavors and aromas. You probably know what that tastes like though, so I'm assuming it wasn't that. I've seen those black spots plenty of times, and I generally trim them, but I don't think they would be likely to give off a strong aroma. Once I had a situation like this where a vegetable tasted of kerosene, which I assumed was a cross-contamination and dumped it. That's what I would recommend if this ever occurs again. If in doubt, throw it out.