A kinetic, spectral and theoretical investigation on the role of oxygen in the radiolytic oxidation of a sorbityl cyclic acetal |
| |
Authors: | Gabriella Poggi Mila D’Angelantonio Marialuisa Russo Salvatore S Emmi |
| |
Institution: | (1) Dipartimento di Chimica “G. Ciamician”, Università di Bologna, Via Selmi 2, I-40126 Bologna, Italy;(2) Istituto di Sintesi Organica e Fotoreattivita’ (ISOF) del CNR, Area della Ricerca, Via P. Gobetti 101, I-40129 Bologna, Italy |
| |
Abstract: | The oxidation process of the cyclic acetal sorbitylfurfural (SF) has been thoroughly examined from the kinetic, spectroscopic
and theoretical point of view. Oxidation has been initiated by the radiolitically produced OH radical in the presence of variable
oxygen amounts. Two competing reaction pathways are evidenced which lead to quite different products, although they do not
affect the acetal ring integrity. The peroxidation of the hydroxylated furanic ring (k
4=(6.1±0.9)×108 M−1 s−1) maintains the ring structurevia HO2• elimination (k
6=(1.9±0.4)×105 s−1). Unlike that, the peroxidation of the pseudo-allylic radical (k
5=(1.9±0.9)×109 M−1 s−1), formedvia β-cleavage, fixes the destructured intermediate, leading to a tetroxide, which slowly decomposes through a Russell mechanism
(k
8=(2.3±0.6)×102 s−1). It is confirmed that the steady state concentration of the tetroxide is very low, which suggests a molar absorption coefficient
for it around 1.2×104 M−1 cm−1 at 265 nm. The end products of the latter pathway have been characterized as carboxylic and butenald-sorbitol derivatives. The kinetic and spectral data of every step of the process have been fitted by the above outlined mechanism.
The energetics of the mechanism has been detailed byab initio computations as well, carrying further substantiation to it. Semi-empirical calculations were also employed to describe the
spectral properties of each intermediate. |
| |
Keywords: | Sorbitylfurfural furalglucitol CAS 7089-59-0 radiolysis radical oxidation non-linear fitting ab initio semi-empirical calculations peroxyl radicals |
本文献已被 SpringerLink 等数据库收录! |
|