ESR spectroscopy has been used to study the formation of free radicals
in the Maillard browning
reaction, from the reaction between glycolaldehyde or glyceraldehyde
and N,N‘-dialkylethylenediamines (alkyl = methyl, ethyl, iso-propyl,
tert-butyl) in either aqueous buffer or in methanol.
Two
series of cyclic cation radicals are formed. The first is a 1:1
sugar:amine product in which the nitrogen
atoms in 1 ethylenediamine molecule are bridged by a sugar molecule.
The second, and more stable,
is a 2:2 product in which a substituted dihydropyrazine cation radical
is formed by the bridging of
two amines with two sugars. In addition, nitroxide radicals are
also observed when methanol is
used as the solvent. A mechanism for the formation of these
radicals in the early stages of the
Maillard reaction is proposed.
Keywords: Maillard reaction; cation radicals; ESR;
dihydropyrazines
Catalytic liquid and vapor phase proceesea for the preparation of %butenenitrile from allyl chloride and hydrogen cyanide are described. Various sulfides were prepared by the free radical-catalyzed addition of thiols to 3-butenenitrile1 bbutenoic acid and esters, and were oxidized to the respective sulfones. Relative rates of isomerization of 3-butenenitrile to 2-butenenitrile using various amine catalysts were determined.
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