I don’t know much about chemistry or alcohol, so please bear with me for a moment.
At what point does wheat- or barley-derived ethanol become Chametz? Is it naturally Chametz, or does it require a catalyst to ferment?
A quick internet search indicates that typically, at least at the industrial level, the grain is milled and mixed with water as part of the initial processing which later leads to fermentation. Once the grain touches the water, the 18-minute clock starts ticking, leading to Chametz even if there is no actual measurable fermentation or visible rising. Fermenting requires yeast (or a chemical means of transforming the starch/sugar into alcohol. But Chametz doesn't require that - it just requires grain + water + time.