Effect of reaction pH on enolization
and racemization reactions of glucose and fructose on heating with amino acid enantiomers and formation of melanoidins as result of the Maillard reaction.
The absence of these signals in the spectra of the complexes indicate coordination through the phenolic oxygen and enolization
of the -C=O of the aroyl keto group and consequent deprotonation.
Strong acidifying effect of the substituents Y and Z is required for enolization
. These problems were studied already seventy years ago by Arndt and co-workers [1-4].
Our interest in enolizable ketones resulted in a recent paper reporting on the syntheses and enolization
of 4-alkyl-2-(2-pyridyl) cyclohexanones (Sund et al., 1991).
From the IR data in Table 7, it was analyzed that L1 acts as a tridentate ligand by coordinating through -O of the deprotonated phenolic group, -O of another deprotonated -OH group formed due to enolization
, and -N of the azomethine group.
The bands in the region of 1437-1440 [cm.sup.-1] in the metal complexes have been assigned to [nu](C-O) [33,39] resulting from enolization
and deprotonation before coordination [14, 40].
The reaction mixture was stirred for further 45 minutes to ensure the complete enolization
. Then Et3N (1.39 mL, 1.016 g, 10.03 mmol, 1.5 eq) and Et3SiOTf (2.30 mL, 2.652 g, 10.03 mmol, 1.5 eq) were successively added and after 15 minutes the cooling bath was removed.
It has been reported in the literature that in alkaline medium sugar will form enediol with the hydroxyl group and also that the rate of enolization
is the same as the rate of oxidation  However, in the present study, the double reciprocal plots of the pseudo-first-order rate constants against the sugar concentrations were linear (fig.
The formation of possible kinetic enolization
products (4-oxygenated products) was not observed.
 proposed the acid-catalyzed enolization
of ionic mechanism for the first time to explore the synthesis of [alpha]-chloropropanoic acid.
and Hydration of Cyclic [beta]-Amino Ketones in the Presence of Water.
This also confirms the deprotonation of imide -NH group through enolization
(the appearance of >C=N stretching band observed in IR spectra).