Chloropentene

Chloropentene is an organochlorine alkene with the molecular formula C5H9Cl. The compound is represented by the structural formula CH2=CHCH2CH2Cl, denoting a five‑carbon chain in which a chlorine atom is attached to the terminal carbon adjacent to the double bond. The IUPAC name is 4‑chloropent-1‑ene, and its other common designation is 4‑chloro‑1‑pentene. The CAS Registry Number for this compound is 104‑03‑1, and it is listed as a colorless to pale yellow liquid with a faint chloroalkene odor at room temperature.

Physical characteristics include a boiling point of approximately 140 °C, a melting point near −212 °C, and a density of about 0.89 g cm−3. Chloropentene is moderately soluble in polar solvents such as ethanol and methanol but only sparingly soluble in water. The double bond imparts unsaturation, allowing for typical alkene reactions such as hydrogenation, halogen addition, and polymerization.

Synthesis routes commonly involve the selective chlorination of 1‑pentene using a chlorine source under controlled conditions. Another laboratory method is the hydrohalogenation of 4‑pentene with HCl, yielding 4‑chloropent-1‑ene with high regioselectivity. In industrial contexts, chloropentene may be produced as a by‑product in processes that chlorinate pentenes or during the synthesis of chlorinated solvents.

Applications of chloropentene are primarily in the production of polymer precursors and as a monomer for polymerization reactions. It can be polymerized to form linear chlorinated polyenes used in specialty plastics and coatings. Moreover, chloropentene serves as an intermediate in the synthesis of fine chemicals, including certain pharmaceuticals and fragrance molecules. Although it is not a major commercial commodity, it finds niche usage in research laboratories for studying alkene reactivity and organochlorine chemistry.

Safety handling of chloropentene requires standard precautions for reactive organohalogens. It is flammable, and its vapors can irritate the skin, eyes, and respiratory tract. Exposure should be minimized with proper ventilation and the use of gloves and goggles. In case of spill, the substance should be contained and removed following hazardous waste protocols, with particular attention to its potential to produce corrosive by‑products when exposed to strong bases or oxidizers.