Treatment of D-glucose with HI (hydriodic acid) results in its reduction to hexyl iodide, with subsequent breakdown into smaller molecules like hexane and iodine. This reaction is a reduction of the aldehyde group in glucose.Treatment of D-glucose with concentrated nitric acid (HNO3) causes oxidation, transforming the aldehyde group into a carboxylic acid group, thereby producing glucaric acid. The oxidation specifically targets the aldehyde functional group.