Diethyl 5-hydroxyisophthalate is primarily used as an intermediate in the synthesis of more complex chemical compounds. It plays a significant role in the production of polymers and resins, where it contributes to the enhancement of material properties such as durability and thermal stability. Additionally, it is utilized in the development of certain pharmaceuticals, aiding in the creation of active pharmaceutical ingredients (APIs) that require specific structural features for efficacy. In the field of organic chemistry, it serves as a building block for the synthesis of various organic molecules, including dyes and pigments, due to its reactive hydroxyl and ester functional groups. Its application extends to research and development, where it is employed in the study of chemical reactions and the design of new materials with tailored properties.