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Tautomerism of 4-phenyl-2,4-dioxobutanoic acid. Insights from pH ramping NMR study and quantum chemical calculations. / Cvijetic, Ilija; Pesic, Milos P.; Todorov, Miljana D.; Juranic, Ivan O.; Drakulic, Branko J.; Verbic, Tatjana; Zloh, Mire.

In: Structural Chemistry, 30.09.2017.

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Cvijetic, Ilija ; Pesic, Milos P. ; Todorov, Miljana D. ; Juranic, Ivan O. ; Drakulic, Branko J. ; Verbic, Tatjana ; Zloh, Mire. / Tautomerism of 4-phenyl-2,4-dioxobutanoic acid. Insights from pH ramping NMR study and quantum chemical calculations. In: Structural Chemistry. 2017.

Bibtex

@article{d74aafafe83a459e82f6cf8835d36ef9,
title = "Tautomerism of 4-phenyl-2,4-dioxobutanoic acid. Insights from pH ramping NMR study and quantum chemical calculations",
abstract = "Aryldiketo acids (ADKs) exhibit the variety of biological activities, mainly due to large affinity toward divalent metal ions. Metal complexation ability of ADKs, as well as interactions with proteins, depend on tautomeric form present in solution. The main aim of this study was to fully explore the tautomeric preferences of 4-phenyl-2,4-dioxobutanoic acid (4PDA), as ADKs representative, in aqueous media at different pH values. 1D and 2D NMR spectroscopy in combination with quantum chemical calculations was applied in order to better understand the tautomeric preferences of 4PDA. The data in highly acidic media are especially interesting since there are no such findings in the literature due to low solubility of ADKs in molecular form. At low pH values, where 4PDA is unionized, the most abundant tautomeric form is enol with keto group closer to phenyl ring. At higher pH values, mixture of two 4PDA ionic forms coexists in solution. Their ratio calculated according to NMR data fits the values predicted using two experimentally determined pKa values. Based on the complexity of 1H NMR spectrum of monoanionic 4PDA form, coexistence of two stable rotamers was assumed. In an alkaline media 4PDA is mostly present in dianionic form. As π-electrons of dianion are delocalized over an entire keto-enol moiety, spectral distinction between tautomers was not possible. Quantum chemical calculations were used to predict relative stability of tautomers. The predictions were in good accordance with experimental results only in case when explicit water molecule was included in calculations. ",
keywords = "Aryldiketo acid, keto-enol tautomerism, NMR spectroscopy, quantum chemical calculations",
author = "Ilija Cvijetic and Pesic, {Milos P.} and Todorov, {Miljana D.} and Juranic, {Ivan O.} and Drakulic, {Branko J.} and Tatjana Verbic and Mire Zloh",
note = "This document is the Accepted Manuscript version of the following article: Cvijeti{\'c}, I.N., Pe{\v s}i{\'c}, M.P., Todorov, M.D. et al, 'Tautomerism of 4-phenyl-2,4-dioxobutanoic acid. Insights from pH ramping NMR study and quantum chemical calculations', Structural Chemistry, September 2017. Under embargo. Embargo end date: 30 September 2018. The final publication is available at Springer via https://doi.org/10.1007/s11224-017-1039-3.",
year = "2017",
month = sep,
day = "30",
doi = "10.1007/s11224-017-1039-3",
language = "English",
journal = "Structural Chemistry",
issn = "1040-0400",
publisher = "Springer New York",

}

RIS

TY - JOUR

T1 - Tautomerism of 4-phenyl-2,4-dioxobutanoic acid. Insights from pH ramping NMR study and quantum chemical calculations

AU - Cvijetic, Ilija

AU - Pesic, Milos P.

AU - Todorov, Miljana D.

AU - Juranic, Ivan O.

AU - Drakulic, Branko J.

AU - Verbic, Tatjana

AU - Zloh, Mire

N1 - This document is the Accepted Manuscript version of the following article: Cvijetić, I.N., Pešić, M.P., Todorov, M.D. et al, 'Tautomerism of 4-phenyl-2,4-dioxobutanoic acid. Insights from pH ramping NMR study and quantum chemical calculations', Structural Chemistry, September 2017. Under embargo. Embargo end date: 30 September 2018. The final publication is available at Springer via https://doi.org/10.1007/s11224-017-1039-3.

PY - 2017/9/30

Y1 - 2017/9/30

N2 - Aryldiketo acids (ADKs) exhibit the variety of biological activities, mainly due to large affinity toward divalent metal ions. Metal complexation ability of ADKs, as well as interactions with proteins, depend on tautomeric form present in solution. The main aim of this study was to fully explore the tautomeric preferences of 4-phenyl-2,4-dioxobutanoic acid (4PDA), as ADKs representative, in aqueous media at different pH values. 1D and 2D NMR spectroscopy in combination with quantum chemical calculations was applied in order to better understand the tautomeric preferences of 4PDA. The data in highly acidic media are especially interesting since there are no such findings in the literature due to low solubility of ADKs in molecular form. At low pH values, where 4PDA is unionized, the most abundant tautomeric form is enol with keto group closer to phenyl ring. At higher pH values, mixture of two 4PDA ionic forms coexists in solution. Their ratio calculated according to NMR data fits the values predicted using two experimentally determined pKa values. Based on the complexity of 1H NMR spectrum of monoanionic 4PDA form, coexistence of two stable rotamers was assumed. In an alkaline media 4PDA is mostly present in dianionic form. As π-electrons of dianion are delocalized over an entire keto-enol moiety, spectral distinction between tautomers was not possible. Quantum chemical calculations were used to predict relative stability of tautomers. The predictions were in good accordance with experimental results only in case when explicit water molecule was included in calculations.

AB - Aryldiketo acids (ADKs) exhibit the variety of biological activities, mainly due to large affinity toward divalent metal ions. Metal complexation ability of ADKs, as well as interactions with proteins, depend on tautomeric form present in solution. The main aim of this study was to fully explore the tautomeric preferences of 4-phenyl-2,4-dioxobutanoic acid (4PDA), as ADKs representative, in aqueous media at different pH values. 1D and 2D NMR spectroscopy in combination with quantum chemical calculations was applied in order to better understand the tautomeric preferences of 4PDA. The data in highly acidic media are especially interesting since there are no such findings in the literature due to low solubility of ADKs in molecular form. At low pH values, where 4PDA is unionized, the most abundant tautomeric form is enol with keto group closer to phenyl ring. At higher pH values, mixture of two 4PDA ionic forms coexists in solution. Their ratio calculated according to NMR data fits the values predicted using two experimentally determined pKa values. Based on the complexity of 1H NMR spectrum of monoanionic 4PDA form, coexistence of two stable rotamers was assumed. In an alkaline media 4PDA is mostly present in dianionic form. As π-electrons of dianion are delocalized over an entire keto-enol moiety, spectral distinction between tautomers was not possible. Quantum chemical calculations were used to predict relative stability of tautomers. The predictions were in good accordance with experimental results only in case when explicit water molecule was included in calculations.

KW - Aryldiketo acid

KW - keto-enol tautomerism

KW - NMR spectroscopy

KW - quantum chemical calculations

U2 - 10.1007/s11224-017-1039-3

DO - 10.1007/s11224-017-1039-3

M3 - Article

JO - Structural Chemistry

JF - Structural Chemistry

SN - 1040-0400

ER -