Kricheldorf and Schwarz [26] have proposed an "
enolization mechanism" for the cis/trans isomerization (Fig.
This is omitting hydrogen relocation through tautomerism followed by the
enolization process.
[45] and connected with increasing tyrosyl radical formation effected in dityrosine generation after isomerization, diradical reaction, and
enolization. Xia et al.
Color of melanoidins might be connected with the
enolization of sugars and racemization of amino acids (Kim & Lee, 2008).
S1 in Supplementary Material available online at https://doi.org/10.1155/2017/ 7520640) and Zn(II) complex (Figure 2), the absence of the v(N-H) and v(C=O) peak in the IR spectrum of Zn(II) complex indicates
enolization of keto group in L1, which coordinated to the Zn metal center through enolate oxygen.
According to these results bromination selectivity occurred at a-carbon of the ketone favorable to
enolization. All these reagents are readily accessible, easily storable in comparison with molecular bromine, less hazardous, easy to handle and facilitate maintenance of the stoichiometric ratio while carrying out the reaction.
The observed results were quantified using NMR spectroscopy with an internal standard leading to a general process that could potentially negate the need for the traditional three step process of oxidation,
enolization, and 0-alkylation.
(1) The N(3)-N(13) and C(4)-N(13) bond lengths become somewhat longer owing/to the coordination with ligand HNMAMQ which takes place via N atoms of the azomethine (>C=N) group that was formed on
enolization of (CO) group in all complexes [38].
In acidic medium, 5-oxoacids undergo
enolization, and on selective oxidation, they result in malonic and substituted benzoic acids, which find widespread applications in synthetic organic chemistry.
The IR spectra of the Schiff base ligands (1a-3a) exhibit a strong band in the range 3026-3180 [cm.sup.-1]and 1672-1679 [cm.sup.-1] due to vNH and vC=O groups respectively, which disappears in the corresponding complexes suggesting the
enolization of the -C=O of the aroyl keto group giving rise to the -C=N-N=C moiety [15 ] and consequent deprotonation upon coordination.
The
enolization ability of the carbonyl group is well known.