Girard's Reagent D is widely used in organic chemistry for the selective isolation and purification of carbonyl compounds, particularly ketones and aldehydes. It reacts with these compounds to form water-soluble hydrazones, which can be easily separated from non-carbonyl components in a mixture. This property makes it valuable in analytical chemistry for the identification and quantification of carbonyl-containing substances. Additionally, it is employed in the synthesis of complex organic molecules, where it aids in the protection and deprotection of carbonyl groups during multi-step reactions. Its ability to selectively target carbonyl groups also makes it useful in the purification of natural products and pharmaceuticals.