中文摘要：

多溴联苯醚（PBDEs）同系物有209种,溴取代数和位置不同,对其空间结构稳定性有影响,PBDEs分子平面可能会发生扭转,继而影响它们的物理化学性质,因此研究最稳定的存在构型及溴取代对PBDEs平面结构的影响尤为重要.本文以多溴联苯醚为研究对象,通过Gaussian03软件在B3LYP/6-31G＊水平下运用量子化学方法分别对PBDEs进行强制平面结构优化和非平面结构优化,并对数据进行分析得出Br取代对PBDEs分子结构的影响.结果表明,所考察的PBDEs均为非平面结构更稳定,即Br取代会引起PBDEs平面结构扭转.从分子的量子化学参数分析,非平面结构优化的PBDEs的醚键键角（θ（C—O—C））变小,1,1＇位键长（R（C1—O）、R（O—C1＇））和6,6＇位键长（R（C6—＊）、R（C6＇—＊））增大,偶极距μ值增大,但二面角（D）大小与R（C6—＊）、R（C6＇—＊）无明显变化规律.

英文摘要：

There are 209 homologs of polybrominated diphenyl ethers（ PBDEs）. The number and location of bromine substitution have great effects on their structures. The substitution of bromine may caused the torsion of the plane of PBDEs,which will affect their physical and chemical properties.Therefore,it is important to find out the most stable configuration of PBDEs and the influence of bromine substitution on the planar structure of PBDEs. Quantum chemistry calculations at B3 LYP /6-31G＊ levels using Gaussian 03 software were performed to optimize the structure of the PBDEs,and the effects of different bromine substitution on the planarity of the two benzene rings in PBDEs molecules were analyzed. The results showed that non-planar structure were relatively stable when PBDEs are substituted by bromine atoms. The substitution of bromine apparently caused the torsion of the plane of PBDEs. According to the calculation of structural theoretical chemistry,θC—O—Cvalues of non-planar structure optimized PBDEs were lower,while R（C1—O）,R（O—C1）,R（C6—＊）,R（C6＇—＊）and μwere higher as compared with the planar structure optimized PBDEs. The substitution of bromine altered D,but no correlations were observed between R（C6—＊）,R（C6＇—＊）and D.