Računalno istraživanje reakcija slobodnih radikala s halogeniranim organskim spojevima u vodenim otopinama

Abstract

U disertaciji su istraženi mehanizmi i kinetike reakcija slobodnih radikala s halogeniranim organskim spojevima u nepuferiranim i puferiranim (bikarbonatnim i fosfatnim) vodenim otopinama. Rad obuhvaća istraživanje reaktivnosti α-aminoalkilnih C-radikala: α-aminoetilnog (•CH(CH_3 ) NH_2) i N-metil--aminoetilnog (•CH(CH_3 ) NHCH_3), zatim glicil radikal aniona (•CH(NH_2 ) COO^-) i atoma vodika (H^•) s trima halogenacetatima – klor-, brom- i jodacetatom – te s halogeniranom nukleobazom 5-bromuracilom. U reakcijama je uočeno nekoliko kompetitivnih mehanizama, od kojih je najznačajniji spregnuti prijenos protona i elektrona (PCET). Otapalo voda isprva je opisano implicitno, modelom PCM, a potom je istražen utjecaj eksplicitne molekule vode na mehanizme i reakcijsku energetiku. Na temelju parametara izračunatih teorijom funkcionala elektronske gustoće (DFT) određeni su dominantni reakcijski mehanizmi i kinetike reakcija. Kod izračuna konstanti brzina uporabljena je konvencionalna teorija prijelaznog stanja i njezina varijacijska inačica uz semiklasične popravke na tuneliranje. Sustavnim istraživanjem izmjensko-korelacijskih funkcionala duž Jakovljevih ljestvi DFT-a nađeni su funkcionali koji daju najbolje slaganje s izmjerenim konstantama brzina za niz radikalskih reakcija.In this doctoral thesis the reaction mechanisms and kinetics of free radical reactions with halogenated organic compounds in non-buffered and buffered (bicarbonate and phosphate) aqueous solutions were investigated. This includes a study of the reactivity of C-centered α-aminoalkyl radicals: •CH(CH_3 ) NH_2, •CH(CH_3 ) NHCH_3, glycyl radical anion •CH(NH_2 ) COO^- and hydrogen atom (H^•) with haloacetates: chloro-, bromo- and iodoacetate and a halogenated nucleobase 5-bromouracil. Reactions exhibit a variety of fundamentally important competing mechanisms, of which the most important one is the proton coupled electron transfer. The solvent was initially described implicitly, and then the influence of explicit water molecules on the mechanisms and reaction energetics was explored. Based on the parameters calculated by the theory of density functional theory (DFT), the dominant reaction mechanisms and reaction kinetics were determined. The reaction rate constants were calculated employing the conventional and variational transition state theory with semiclassical corrections for the tunneling. By systematically climbing up the Jacob's ladders of DFT, for the set of radical reactions, we investigated which types of exchange-correlation functionals produce the rate constants in best agreement with the measured ones