Radiation chemistry of carbohydrates. Part XVI. The contribution of OH radicals to the radiolysis of aqueous solutions

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Abstract
Experiments using 60Co γ-radiation show that the radiation degradation of D-glucose is chemically and kinetically different at 5 × 10–4 M and at 5 × 10–2 M. Scavenging experiments using potassium iodide, and the effects of solute concentration on product yields, support the view that abstraction by ·OH radicals initiates chemical change at ⩽ 5 × 10+3 M. Pulse-radiolysis experiments using 4-MeV electrons show that there is no significant reaction of e–(aq) with carbohydrates. For the reaction e–(aq)+D-glucose k2 < 107 mole–1 sec.–1 at 5 × 10–3 M-D-glucose. A transient species with an absorption maximum at 2600–2700 Å is observed on pulsing, which decays by second-order kinetics within the solute range 5 × 10–3 to 5 × 10–1 M in solutions saturated with argon and nitrous oxide. Evidence is presented that the transient species is produced as a result of abstraction by the ·OH radical. Complete scavenging of the ·OH occurs at 5 × 10–3 M. The further decomposition of D-glucose at higher concentrations is due to another process which may involve energy transfer from excited water molecules.

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