Theoretical Study On The Reaction Mechanism Of OH Radical And Polybromobenzene Of Flame Retardant

Brominated flame retardants(BRFs)have been widely used in many commercial products such as electrical products,textiles and furnishings.BFRs are one of the most widely used flame retardants in the world..Brominated flame retardants are the most widely produced and used polybrominated diphenyl ethers(PBDEs)and hexabromocyclododecane(HBCDs),but ftetra-,penta-,hexa-and hepta-BDEs and HBCD have been banned because of their biotoxicity.New flame retardants such as Polybromobenzenes have been produced as alternatives of PBDEs and HBCDs.The polybromobenzenes from production or degradation of other BRFs can enter into the environment.Polybromobenzenes are persistent in the environment.They can undergo migration with the atmospheric transport process.The semi-volatile,biotoxic and long-distance researchers of polybromobenzenes have been caused by the attention.However,the behavior of polybromobenzenes in the environment is still vague.The reaction process of polybromobenzenes with free-radical is easily influenced by many factors and difficult to be revealed experimentally.In this thesis,as an method of quantum chemistry calculation have been used to study the crucial process of the transformation of several typical polybromobenzenes and OH radicals in the atmospheric environment.The reaction rate constants of critical elementary processes were calculated using canonical variational transition-state theory(CVT)with small curvature tunneling corrections(SCT).The important and meaningful results in this thesis can be summarized as follows:The reactions of hexabromobenzene(HBB),1,2,4,5-tetrabromobenzenes(1,2,4,5-TeBB),pentabromobenzene(PeBB),pentabromoethylbenzene(PBEB),pentabromotoluene(PBT),2,4,5-tribromotoluene(2,4,5-TrBT)and 1,2,3,5-tetrabromobenzenes(1,2,3,5-TeBB)with OH radical have been explored at the level of MPWB1K/6-311+g(3df,2p)//MPWB1K/6-31+g(d,p).The reaction of polybromobenzenes with OH radicals shows that the less bromine atoms in the benzene ring is more active.The barrier of OH radical added to the carbon atoms connected to the bromine atoms is higher than the barrier of OH radical added to other carbon atoms in OH radicals addition reactions.At 298 K,The rate constants of OH radicals with HBB,1,2,4,5-TeBB,PeBB,PBEB,PBT 2,4,5-TrBT and 1,2,3,5-TeBB are determined to be 5.72×10-13 cm3 molecule-1s-1,1.23×10-12 cm3 molecule-1s-1,8.78×10-13 cm3molecule-1s-1,9.23×10-13 cm3molecule-1s-1,6.46×10-13 cm3molecule-1s-1,1.69×10-12 cm3 molecule-1s-1 and 1.32×10-12cm3 molecule-1s-1.The estimated atmospheric lifetimes of HBB(9.65 days),1,2,4,5-TeBB(7.0 days),PeBB(12.9 days),PBEB(13.5 days),PBT(20.8 days)2,4,5-TrBT(18.4 days)and 1,2,3,5-TeBB(8.99 days)determined by OH radicals indicate.With considering other processes,polybromobenzenes have long atmospheric lifetime.