Trans-3-pentenoic acid is primarily used in organic synthesis as a building block for more complex chemical compounds. It serves as an intermediate in the production of pharmaceuticals, agrochemicals, and specialty chemicals. Its unsaturated structure makes it valuable for creating polymers and resins with specific properties, such as flexibility or durability. Additionally, it is utilized in the synthesis of fragrances and flavors, contributing to unique aromatic profiles. In research, it is employed as a reagent to study reaction mechanisms and develop new synthetic pathways. Its versatility in various chemical processes highlights its importance in industrial and academic applications.