S. Nomoto et al., UNDER-FLAME OXIDATION OF AMINES AND AMINO-ACIDS IN AN AQUEOUS-SOLUTION, Bioscience, biotechnology, and biochemistry, 60(11), 1996, pp. 1851-1855
Flames from town gas-oxygen, hydrogen-oxygen, and ethylene-oxygen mixt
ures, when blown against the surface of an aqueous solution of amines
and amino acids, induced an oxidation reaction in the aqueous phase, w
hile an acetylene-oxygen flame failed to oxidize the compounds in solu
tion. The hydrogen flame caused direct hydroxylation of the aromatic r
ings of phenylglycine homologs. The isomeric ratio of o-, m-, and p-hy
droxyphenyl-amino acids produced was in accordance with that obtained
by using the reaction systems of Fe2+-H2O2-EDTA and Fe2+-ascorbic acid
-H2O2-EDTA, which are known to involve a hydroxyl radical as the agent
for hydroxylating the aromatic rings. These results strongly suggest
that the active species of flame-induced oxidation in an aqueous solut
ion was the hydroxyl radical which was produced in the flames and extr
acted into the aqueous phase.