NMR and computational studies on tautomerism of 3-hydroxy-2-(2-thienylcarbonyl)cyclohex-2-en-1-one

Chans, Guillermo M.; Moyano, Elizabeth L.; Baumgartner, María T.

doi:10.1016/j.molstruc.2013.11.057

Cited by 3 publications

(2 citation statements)

References 34 publications

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“…The ground state geometry of all possible tautomers and conformers for 1 , 2 and 3 were fully optimized employing the Gaussian09 program suite [ 15 ], in a similar way to our previous works [ 16 ]. The hybrid B3LYP functional method [ 17 , 18 ] was used in combination with the 6-31+G(d,p) basis set for the expansion of the Kohn-Sham orbitals for all the atoms.…”

Section: Theoretical Calculationsmentioning

confidence: 99%

Photolysis, tautomerism and conformational analysis of dehydroacetic acid and a comparison with 2-hydroxyacetophenone and 2-acetyl-1,3-cyclohexanodione

Cooke

Chans

Argüello

et al. 2020

Heliyon

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The purpose of this work was to determine the tautomerism, the conformational analysis and photoreactivity of dehydroacetic acid (DHAA, 1 ). For that reason, the photolysis of DHAA ( 1 ) was performed at 254 nm and compared with two structurally similar compounds: 2-hydroxyacetophenone (HAP, 2 ) and 2-acetyl-1,3-cyclohexanodione (ACH, 3 ). We confirmed the degradation of 1 to acetic acid and we propose a mechanism on the assumption that a [2+2] cyclodimerization occurs (after UV light absorption) followed by some consecutive Norrish Type I cleavages, affording ketenes that end-up in acetic acid. The UV absorption study was conducted for all three compounds to gain insight about their electronic transitions, both experimentally and with computational simulations using TDDFT (B3LYP/6-31+G(d,p)) methods. A detailed analysis of the different tautomers and isomers that can be present in solution and the MOs involved in the electronic transitions was also achieved. The HOMO→LUMO transition was the least energetic optically active transition for 1 and 2 , whereas 3 was recognized to have a HOMO-1→LUMO transition. These transitions were all of n→π ∗ character.

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Section: Theoretical Calculationsmentioning

confidence: 99%

Photolysis, tautomerism and conformational analysis of dehydroacetic acid and a comparison with 2-hydroxyacetophenone and 2-acetyl-1,3-cyclohexanodione

Cooke

Chans

Argüello

et al. 2020

Heliyon

Self Cite

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“…The NMR measurements can give precise and microscopic information on the nature of the protonation equilibria and tautomerism behavior. [73][74][75][76][77][78] The outstanding informative merit of NMR is revealed in itself in providing quantitative information on an equilibrium system, i.e. in determination of protonation constants as well as in providing information on a molecular structure.…”

Section: Protonation and Lactam-lactim Tautomerism Equilibriamentioning

confidence: 99%

Synthesis, protonation equilibrium and peculiar thermal decomposition behavior of cyclo-tri-μ-imidotetraphosphate

et al. 2014

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The synthesis and isolation of the sodium salt of cyclo-tri-μ-imidotetraphosphate, i.e. Na4cP4O9(NH)3·H2O, were achieved by the hydrolysis of Na4cP4O8(NH)4·2H2O under very weak acidic conditions, i.e. using 0.2 mol L(-1) propionic acid and the pH-controlled recrystallization procedure. The purity of Na4cP4O9(NH)3·H2O was improved from 2% to 95% by the pH-controlled recrystallization only two times. The first protonation constants of a series of cyclo-μ-imidotetraphosphate anions, i.e. cP4O(12-n)(NH)n(4-) (n = 0, 2, 3, 4), were determined by potentiometric titration and (31)P NMR chemical shift measurements in aqueous solution. Regardless of the paucity of the purity of trans-cP4O10(NH)2(4-) anions, the protonation processes of all anions may be evaluated accurately without any previous purification, because the NMR signals corresponding to cP4O(12-n)(NH)n(4-) (n = 0, 2, 3, 4) anions are well resolved. The logarithmic first protonation constants increase with a "linear" increase in the number of imino groups which constitute the ligand molecules. Macroscopic protonation reactions could be divided into three microscopic protonation processes for -O-PO2-O-, -O-PO2-NH-, and -NH-PO2-NH- groups. The basicity of the -NH-PO2-NH- group is especially high, because the delocalization of H(+) ions by lactam-lactim tautomerism on the whole ring molecule of cP3O6(NH)3 and cP4O8(NH)4 enhances the protonation of these ligands. In addition, also the concurrent change observed in the (31)P NMR chemical shift values of the phosphorus nuclei in the -O-PO2-NH- and -NH-PO2-NH- groups of cP4O9(NH)3(4-) anions suggested the effect of the lactam-lactim tautomerism. The intrinsic (31)P NMR chemical shifts for the central phosphorus nuclei for -O-PO2-O-, -O-PO2-NH-, and -NH-PO2-NH- groups show a good proportional relationship with the number of nitrogen atoms bonded to the central phosphorus atoms. Two types of imino groups with mutually dissimilar chemical environments which are present in the Na4cP4O9(NH)3 molecule, that is -O-PO2-NH-PO2-NH- and -NH-PO2-NH-PO2-NH-, brought about a two-stage pyrolytic elimination of imino groups from the initial stage of combustion over a wide temperature range.

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Synthesis, NMR and computational studies on tautomerism of dichloroacetate of hydroxyanthraquinone

Zhu

Wang

Miao

et al. 2017

Journal of Molecular Structure

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NMR and computational studies on tautomerism of 3-hydroxy-2-(2-thienylcarbonyl)cyclohex-2-en-1-one

Cited by 3 publications

References 34 publications

Photolysis, tautomerism and conformational analysis of dehydroacetic acid and a comparison with 2-hydroxyacetophenone and 2-acetyl-1,3-cyclohexanodione

Photolysis, tautomerism and conformational analysis of dehydroacetic acid and a comparison with 2-hydroxyacetophenone and 2-acetyl-1,3-cyclohexanodione

Synthesis, protonation equilibrium and peculiar thermal decomposition behavior of cyclo-tri-μ-imidotetraphosphate

Synthesis, NMR and computational studies on tautomerism of dichloroacetate of hydroxyanthraquinone

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