Theoretical study of the mechanism of proton transfer in tautomeric systems: Alloxan

Kakkar, Rita; Sarma, Bhupendra K.; Katoch, Vandana

doi:10.1007/bf02708649

Cited by 7 publications

(8 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We have the following comments on the corresponding data: The most stable among the molecular tautomers is the triketo form 1a , followed by the 6‐hydroxy one 1b . Qualitatively similar results were obtained 17, 19 on the basis of the AM1 semiempirical method. According to Minkin et al 39, prototropic conversions are probable when the energy differences between initial and final structures are ≤25 kJ mol −1 , with activation barriers of ≤105 kJ mol −1 . The energy difference is larger in the present case; nevertheless, 1a and 1b do coexist in solutions.…”

Section: Resultsmentioning

confidence: 99%

“…The most stable among the molecular tautomers is the triketo form 1a , followed by the 6‐hydroxy one 1b . Qualitatively similar results were obtained 17, 19 on the basis of the AM1 semiempirical method.…”

Section: Resultsmentioning

confidence: 99%

“…2,4,6‐Pyrimidinetrione and its derivatives have been studied by Hückel 14, extended Hückel 15, and AM1 16–19 molecular orbital (MO) calculations. The results obtained relate to the deprotonation energies 14, enthalpies of formation, tautomeric 16, 17, 19 and conformational 15, 19 dependence on the energies, intramolecular and intermolecular hydrogen bonds, and their effects on CH acidity 16, 18.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Computational study of energies and structures of 2,4,6‐pyrimidinetrione and its anions

Daskalova

Binev

2005

Int J of Quantum Chemistry

View full text Add to dashboard Cite

Energies and structures of 2,4,6-pyrimidinetrione, its anion, dianion, and trianion have been studied by means of ab initio and density functional computations. According to these studies, the most stable among the molecular tautomers is the triketo form, followed by the 6-hydroxy tautomer, in full agreement with earlier theoretical results and with experimental data on the tautomeric equilibrium. The deprotonation energy of 1345.24 kJ mol Ϫ1 calculated for 2,4,6-pyrimidinetrione, corresponds to a moderately strong COH acid, in accordance with its experimental pK a 1 ϭ 8.4 (solvent dimethylsulfoxide). The calculated structural changes, caused by the molecule 3 monoanion conversion, are in good agreement with those found experimentally. Energy and structural changes, worked by both anion 3 dianion and dianion 3 trianion conversions, have also been computed and discussed.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Computational study of energies and structures of 2,4,6‐pyrimidinetrione and its anions

Daskalova

Binev

2005

Int J of Quantum Chemistry

View full text Add to dashboard Cite

show abstract

“…These newly generated amide proton signals with different 1 H and 15 N chemical shis from the unused BTA molecule were derived from the STOBA products. Because of the highly delocalized electronic density character of BTA, when the a-methylene carbon of BTA interacted with the C]C double bond of MDA-BMI, the 1 H and 15 N signals shied. This conclusion applies to most barbiturate drugs whose a-methylene protons are substituted by some other functional groups and the amide protons are retained.…”

Section: Resultsmentioning

confidence: 99%

“…[2][3][4][5][6][7][8][9][10][11] Studies on the reactant barbituric acid (BTA) molecule have focused on the resonance structures of its electron density distribution calculations and tautomerization properties. [12][13][14][15][16][17][18] Polymerizing BMI with ethylenediamine 7,19 might misguide that the acidity and therefore the active sites of BTA are the amide nitrogen atoms rather than the b-dicarbonyl a-methylene carbon. [20][21][22][23][24][25][26][27][28][29][30][31] Many studies have attempted to optimize the performance of STOBA.…”

Section: Introductionmentioning

confidence: 99%

NMR spectroscopy study on N,N′-bismaleimide-4,4′-diphenylmethane and barbituric acid synthesis reaction mechanism in N,N′-dimethylformamide solvent

et al. 2017

View full text Add to dashboard Cite

show abstract

Tautomerism of quinazolin-4-ones with 2,3-annulated hydrogenated 1,3-diazaheterocycles. Synchronous and asynchronous double proton transfer in cyclic hydrogen-bonded associates

Морковник

Диваева

2009

Russ Chem Bull

View full text Add to dashboard Cite

It was shown by quantum chemical methods and 1 H NMR spectroscopy that in the series of prototropic tautomeric quinazolin 4 ones with hydrogenated 1,3 diazaheterocycles annulated at positions 2 and 3, namely, imidazole, pyrimidine, or [1,3]diazepine (compounds 1-3, respectively), the 1H tautomeric form strongly predominates in the gas phase and in solutions regardless of the nature of these cycles. Tautomerization of tricycles 1-3 occurs via the intermolecular mechanism to form as intermediates hydrogen bonded cyclodimers of these compounds or their cyclosolvates with proton donor solvents. The key step of the reaction is the intraassociated concerted double proton transfer, which can proceed in nearly synchronous and asynchronous modes. In particular, double proton transfer in cyclodimers of quinazolinones 1-3 is asynchronous and proceeds with the formation of solvate stabilized polar transition states, which are similar in structure to ionic intermediates of the nonconcerted double proton transfer.Key words: 2,3 dihydroimidazo[2,1 b]quinazolin 1(10)H 5 one, 1,2,3,4 tetrahydropyr imido[2,1 b]quinazolin 1(11)H 6 one, 2,3,4,5 tetrahydro[1,3]diazepino[2,1 b]quinazolin 1(12)Н 7 one, tautomerism, transition states, homocyclodimers, heterocyclodimers, synchronous double proton transfer, asynchronous double proton transfer, cyclic hydrogen bonded associates.Tricyclic quinazolin 4 ones 1-3 with 2,3 annulated hydrogenated imidazole, pyrimidine, and diazepine heterocycles are interesting objects with structural simi larity to hydrogenated imidazo and pyrimido[1,2 a]benz imidazoles. A series of the latter includes promising pharma cologically active compounds. 1-8 They are also promising as objects for investigation of the influence of intermo lecular hydrogen bonds on the reactivity of heterocycles. 9The data on the biological activity of various N substi tuted quinazolinones 1 and 2 are

show abstract

Theoretical study of the mechanism of proton transfer in tautomeric systems: Alloxan

Cited by 7 publications

References 12 publications

Computational study of energies and structures of 2,4,6‐pyrimidinetrione and its anions

Computational study of energies and structures of 2,4,6‐pyrimidinetrione and its anions

NMR spectroscopy study on N,N′-bismaleimide-4,4′-diphenylmethane and barbituric acid synthesis reaction mechanism in N,N′-dimethylformamide solvent

Tautomerism of quinazolin-4-ones with 2,3-annulated hydrogenated 1,3-diazaheterocycles. Synchronous and asynchronous double proton transfer in cyclic hydrogen-bonded associates

Contact Info

Product

Resources

About