“…The rest of the bands (Table ) are associated with methyl groups and aromatic ring vibrations. Thus, the infrared spectra provide experimental evidence that thione is the dominant species in the solid state, in agreement with earlier reports in the literature. ,, 2 Experimental FTIR spectrum of the solid 4,6-dimethyl-2-mercaptopyrimidine sample.…”
Section: Resultssupporting
confidence: 90%
“…Thus, the band at 2835 cm -1 should be attributed to the υ(NH···S) interaction . A weak band observed at 1728 cm -1 could be responsible for the SCN group . The vibration of the NHCS group shows peaks at 1225 and 1188 cm -1 .…”
Section: Resultsmentioning
confidence: 97%
“…NMR studies also provide evidence concerning the predominance of the thione structure; inclusively, the prototropic interconversion between the tautomers has been reported , …”
Section: Introductionmentioning
confidence: 95%
“…13 Infrared is another valuable instrument to investigate the chemical structure of these compounds and derivatives and has allowed several experiments to be performed the results of which allow full interpretation of their vibrational spectra. 14,15 These compounds belong to a class of reagents that are very useful in organic synthesis because they offer the possibility of investigating alternative routes to conventional processes, specifically that involving nucleophilic substitutions. 16 However, their full potential is beyond the scope of this article because they have found numerous applications in organometallic chemistry.…”
The tautomeric forms of 4,6-dimethyl-2-mercaptopyrimidine in solution were examined. Experimental support
for the existence of the tautomeric forms of this molecule was provided by infrared (FTIR), ultraviolet (UV),
and nuclear magnetic resonance (NMR) techniques. Density functional theory (DFT) calculations allowed us
to elucidate these molecular structures. The vibrational and electronic spectra, as well as the 1H and 13C
chemical shifts, were satisfactorily described by DFT theoretical calculations. The potential of the DFT
methodology was confirmed by prediction of a band at 2706 cm-1, associated with the stretching vibration
of −SH group, which did not appear in the experimental spectrum because it was overshadowed by the
symmetric and antisymmetric vibration modes of −CH3 groups. The existence of the tautomeric thiol−thione equilibrium of 4,6-dimethyl-2-mercaptopyrimidine with the thione structure dominating in polar solvents
(CH3OH and DMSO-d
6) and the thiol structure in apolar media (cyclohexane) has been demonstrated.
“…The rest of the bands (Table ) are associated with methyl groups and aromatic ring vibrations. Thus, the infrared spectra provide experimental evidence that thione is the dominant species in the solid state, in agreement with earlier reports in the literature. ,, 2 Experimental FTIR spectrum of the solid 4,6-dimethyl-2-mercaptopyrimidine sample.…”
Section: Resultssupporting
confidence: 90%
“…Thus, the band at 2835 cm -1 should be attributed to the υ(NH···S) interaction . A weak band observed at 1728 cm -1 could be responsible for the SCN group . The vibration of the NHCS group shows peaks at 1225 and 1188 cm -1 .…”
Section: Resultsmentioning
confidence: 97%
“…NMR studies also provide evidence concerning the predominance of the thione structure; inclusively, the prototropic interconversion between the tautomers has been reported , …”
Section: Introductionmentioning
confidence: 95%
“…13 Infrared is another valuable instrument to investigate the chemical structure of these compounds and derivatives and has allowed several experiments to be performed the results of which allow full interpretation of their vibrational spectra. 14,15 These compounds belong to a class of reagents that are very useful in organic synthesis because they offer the possibility of investigating alternative routes to conventional processes, specifically that involving nucleophilic substitutions. 16 However, their full potential is beyond the scope of this article because they have found numerous applications in organometallic chemistry.…”
The tautomeric forms of 4,6-dimethyl-2-mercaptopyrimidine in solution were examined. Experimental support
for the existence of the tautomeric forms of this molecule was provided by infrared (FTIR), ultraviolet (UV),
and nuclear magnetic resonance (NMR) techniques. Density functional theory (DFT) calculations allowed us
to elucidate these molecular structures. The vibrational and electronic spectra, as well as the 1H and 13C
chemical shifts, were satisfactorily described by DFT theoretical calculations. The potential of the DFT
methodology was confirmed by prediction of a band at 2706 cm-1, associated with the stretching vibration
of −SH group, which did not appear in the experimental spectrum because it was overshadowed by the
symmetric and antisymmetric vibration modes of −CH3 groups. The existence of the tautomeric thiol−thione equilibrium of 4,6-dimethyl-2-mercaptopyrimidine with the thione structure dominating in polar solvents
(CH3OH and DMSO-d
6) and the thiol structure in apolar media (cyclohexane) has been demonstrated.
“…Various reports had appeared recently discussing the electronic spectral properties of pyrimidine bases and their derivatives [12][13][14][15][16][17][18][19][20][21][22][23]. Pyrimidine is an active component of antibiotics and antineoplastics (e.g.…”
KEYWORDSThe spectral behavior of some new arylazo-2,6-diamino-4-pyrimidinol in pure and mixed organic solvents and buffer solutions of varying pH have been studied. The observed bands are assigned to the possible electronic transition. The band appearing in the visible region is assigned to →* transition involving -electronic system of the whole compounds, associated with intramolecular charge transfer. This charge transfer seems to originate from the aryl moiety to the pyrimidine ring which is characterized by accepting character. This behavior can be explained that these compounds exist in the hydroxyazo-quinoid hydrazon tautomreic explained equilibrium. The possibility of the formation of -H-bond solvated molecular complex between the molecule of azo 2,6-diaminopyrimidinol and proton-acceptor solvents of DMSO and DMF molecular were discussed. The pK values of these compounds were determined and on the basis of the relative contribution of acidic basic character of respective species. pK values Mixed solvents Buffer solutions Spectra behavior Molecular complex Arylazo diaminopyrimidinol
The UV and visible spectra of some arylazo barbituric acids and arylazo pyrimidine in pure and mixed organic solvents of varying polarities have been studied. The different absorption bands displayed in the electronic spectra of these compounds are assigned and the possibility of the existence of these compounds in tautomeric equilibrium as well as in intra‐ and intermolecular H‐bonding were examined. The solute‐solvents molecular complexes liable to exist in polar‐nonpolar mixed solvents are investigated. The structure of the azo compounds were confirmed by 1H NMR and IR spectroscopy. The ionization processes of the compounds were investigated and the possible ionization constants were determined and discussed in terms of molecular structure of the azo compounds.
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