Nitro Memes

The chemical structure shown is pentaerythritol, which has four hydroxyl (OH) groups. The joke is that if you replace all the hydroxyl groups with "completely useless groups" like nitro groups, you wouldn't get water - you'd get a completely different compound (and probably an extremely unstable explosive)! This is chemistry humor at its finest - the person asking the question fundamentally misunderstands how chemical transformations work. You can't just "turn" one molecule into another by replacing functional groups and expect to get water as a product. That's like saying "How do I turn this car into a hamburger by replacing all the wheels with pickles?" Bonus chemistry fact: If you actually did replace those hydroxyl groups with nitro groups, you'd essentially create PETN (pentaerythritol tetranitrate) - a powerful explosive used in detonation cords. So maybe not so "useless" after all... unless your goal was actually making water, then yes, spectacularly useless.