title: Complete catalytic debromination of hexabromocyclododecane using a silica-supported palladium catalyst in alkaline 2-propanol.
abstract: Although the brominated flame retardant 1,2,5,6,9,10-hexabromocyclododecane (HBCD) has been widely used to reduce the flammability of polymeric materials, it is a toxic and persistent organic compound. In this paper, we report an efficient method for the debromination of HBCD by using a Pd-catalyzed system. HBCD was completely debrominated to the C12cyclic compounds such as cyclododecatriene, cyclododecadiene, and cyclododecene in a solution of 2-propanol/methanol (99:1, v/v) containing dissolved NaOH in the presence of a silica-supported Pd catalyst (Pd/SiO2) at 35 °C. The reaction achieved product yields of 92% for the bromine-free products and 94% for the released Br ions. In the absence of Pd/SiO2, HBCD was partially debrominated to yield penta-, tetra-, and tribrominated C12cyclic compounds. The HBCD debromination pathway seems to involve both HBr elimination by reaction with NaOH and Pd-catalyzed hydrodebromination by hydrogen transfer from 2-propanol.
authors.affiliation: National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba West, 16-1 Onogawa, Tsukuba, Ibaraki, 305-8569, Japan. Electronic address: y-ukisu@aist.go.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ukisu
mesh_terms: D019840:2-Propanol; D001966:Bromine; D002384:Catalysis; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005411:Flame Retardants; D054879:Halogenation; D006842:Hydrocarbons, Brominated / Q000737:chemistry*; D006844:Hydrocarbons, Cyclic / Q000138:chemical synthesis*; D006859:Hydrogen / Q000737:chemistry; D000432:Methanol; D010165:Palladium / Q000737:chemistry; D012822:Silicon Dioxide
chemical_list: D005411:Flame Retardants; D006842:Hydrocarbons, Brominated; D006844:Hydrocarbons, Cyclic; C089796:hexabromocyclododecane; D010165:Palladium; D012822:Silicon Dioxide; D006859:Hydrogen; D019840:2-Propanol; D001966:Bromine; D000432:Methanol
keywords: 2-Propanol; Brominated flame retardant; Dehalogenation; Hexabromocyclododecane; Pd catalyst; Sodium hydroxide