1-Ethyl-1-cyclopentene is primarily used in organic synthesis as a building block for more complex chemical compounds. It serves as an intermediate in the production of various pharmaceuticals, agrochemicals, and specialty chemicals. Its structure allows it to participate in reactions such as polymerization, hydrogenation, and cycloaddition, making it valuable in the development of polymers, resins, and other materials. Additionally, it can be utilized in research and development for creating novel compounds with potential applications in medicinal chemistry and material science. Its reactivity and versatility make it a useful component in industrial and laboratory settings.