title: Theoretical investigation of isotope exchange reaction in tritium-contaminated mineral oil in vacuum pump.
abstract: The mechanism of the isotope exchange reaction between molecular tritium and several typical organic molecules in vacuum pump mineral oil has been investigated by density functional theory (DFT), and the reaction rates are determined by conventional transition state theory (TST). The tritium-hydrogen isotope exchange reaction can proceed with two different mechanisms, the direct T-H exchange mechanism and the hyrogenation-dehydrogenation exchange mechanism. In the direct exchange mechanism, the titrated product is obtained through one-step via a four-membered ring hydrogen migration transition state. In the hyrogenation-dehydrogenation exchange mechanism, the T-H exchange could be accomplished by the hydrogenation of the unsaturated bond with tritium followed by the dehydrogenation of HT. Isotope exchange between hydrogen and tritium is selective, and oil containing molecules with OH and COOH groups can more easily exchange hydrogen for tritium. For aldehydes and ketones, the ability of T-H isotope exchange can be determined by the hydrogenation of T2 or the dehydrogenation of HT. The molecules containing one type of hydrogen provide a single product, while the molecules containing different types of hydrogens provide competitive products. The rate constants are presented to quantitatively estimate the selectivity of the products.
authors.affiliation: Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, PR China.
authors.forename: Liang
authors.initials: L
authors.lastname: Dong
authors.affiliation: Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, PR China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Xie
authors.affiliation: Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, PR China; School of Radiation Medicine and Protection (SRMP), School for Radiological and Interdisciplinary Sciences (RAD-X), Suzhou 215000, PR China.
authors.forename: Liang
authors.initials: L
authors.lastname: Du
authors.affiliation: School of Physics and Chemistry, Xihua University, Chengdu 610065, PR China.
authors.forename: Weiyi
authors.initials: W
authors.lastname: Li
authors.affiliation: Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, PR China. Electronic address: zhyitan@126.com.
authors.forename: Zhaoyi
authors.initials: Z
authors.lastname: Tan
mesh_terms: D006865:Hydrogenation; D008899:Mineral Oil / Q000737:chemistry*; D008956:Models, Chemical; D014316:Tritium / Q000737:chemistry*
chemical_list: D014316:Tritium; D008899:Mineral Oil
keywords: DFT; Hydrogen; Isotope exchange; Tritium; Vacuum pump oil