4,5-Dimethylphthalic acid is primarily used in the synthesis of polymers and resins, where it acts as a building block to enhance thermal stability and mechanical properties. It is also employed in the production of plasticizers, which improve the flexibility and durability of plastics. In the pharmaceutical industry, it serves as an intermediate in the synthesis of various active pharmaceutical ingredients (APIs). Additionally, it finds application in the development of dyes and pigments, contributing to color stability and intensity. Its role in organic synthesis extends to the creation of complex molecules for research and industrial purposes.