VIII. Summary

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The hydroxyl radical and the sulfate radical anion both abstract hydrogen atoms from unprotected carbohydrates. In each case first-formed, carbon-centered radicals are produced. The hydroxyl radical is so reactive that it shows little regioselectivity when reacting with D-glucose; that is, spectroscopic evidence indicates that hydrogen-atom abstraction occurs from each of the six carbon atoms in this molecule. The hydroxyl radical remains unselective in reaction with other simple sugars that contain only pyranoid rings, but it does regioselectively abstract H₅' from the furanoid ring in sucrose. The sulfate radical anion is a more selective abstracting agent. Hydrogen-atom abstraction occurs primarily from C-2, C-5, and C-6 in α-D-glucopyranose and at C-1, C-5, and C-6 in β-D-glucopyranose.

First-formed radicals derived from D-glucose undergo acid-catalyzed rearrangement under strongly acidic conditions to produce carbonyl-conjugated radicals. Under basic conditions first-formed radicals produce radical anions that form semidiones. When oxygen is present in the reaction mixture, first-formed radicals react to give peroxy radicals.