H-Atom abstraction by C-centered radicals from cyclic and acyclic dipeptides. A theoretical and experimental study of reaction rates

摘要: Using the pulse radiolysis and other radiation chemical techniques, reaction kinetics of ˙CH3 ˙CH2OH radicals with alanine anhydride, glycine anhydride sarcosine were examined in aqueous solution. The second order rate constant has been determined at 2 × 105 dm3 mol−1 s−1. A very similar value (8 × 104 s−1) obtained by measuring methane ethane yields as a function concentration different dose rates evaluation these data computer analysis. Similar experiments carried out yielded identical constants 4 × 104 s−1 for compounds. It was found that radical does not react an appreciable (k < 2 × 102 s−1). reactions ˙CH3, ˙CH2OH, ˙C(CH3)2OH both cyclic anhydrides acyclic peptides studied means theoretical calculations B3LYP/6-311+G(d,p) level theory. Free energies gaseous phase classical harmonic oscillator–rigid rotator model, used to estimate H-transfer αC-site peptides. effects solution on activation enthalpies estimated SCIPCM procedure. experimental A-factor methyl radical + D,L-alanine reaction, modified Arrhenius A-factors species, calculate solution-phase constants. are discussed terms charge spin polarisation transition state, AIM analysis, orbital interaction Rate constants, calculated state theory good agreement available data.