MONONITROFLUORESCEINS IN AQUEOUS MEDIA: ACID-BASE EQUILIBRIA, TAUTOMERISM, AND HYDROLYSIS OF DIACETATES

MONONITROFLUORESCEINS IN AQUEOUS MEDIA: ACID-BASE EQUILIBRIA, TAUTOMERISM, AND HYDROLYSIS OF DIACETATES

This article reports equilibrium and kinetic data for three fluorescein dyes containing the nitro group in the residue of the phthalic acid, 3'-, 4'-, and 5'-nitrofluorescein, in water and 50 mass % aqueous ethanol. These compounds, particularly the recently synthesized 3'-nitrof...

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Дата:2024
Автори: Kharchenko, Daria, Shekhovtsov, Sergiy, Cheipesh, Tetiana, Mchedlov-Petrossyan, Mykola
Формат: Стаття
Мова:English
Опубліковано: V.I.Vernadsky Institute of General and Inorganic Chemistry 2024
Онлайн доступ:https://ucj.org.ua/index.php/journal/article/view/687
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Назва журналу:Ukrainian Chemistry Journal

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Ukrainian Chemistry Journal
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spelling oai:ojs2.1444248.nisspano.web.hosting-test.net:article-6872025-03-21T18:56:14Z MONONITROFLUORESCEINS IN AQUEOUS MEDIA: ACID-BASE EQUILIBRIA, TAUTOMERISM, AND HYDROLYSIS OF DIACETATES Kharchenko, Daria Shekhovtsov, Sergiy Cheipesh, Tetiana Mchedlov-Petrossyan, Mykola Nitrofluorescein; acid-base dissociation; water-ethanol binary solvent; absorption spectra; dissociation constants; tautomerism; diacetylfluorescein; two-step alkaline hyd­ro­lysis; rate constants. This article reports equilibrium and kinetic data for three fluorescein dyes containing the nitro group in the residue of the phthalic acid, 3'-, 4'-, and 5'-nitrofluorescein, in water and 50 mass % aqueous ethanol. These compounds, particularly the recently synthesized 3'-nitrofluorescein, were less considered polyprotic acids than many other fluorescein dyes. The dyes behave as diprotic acids, which can also be protonated: H3R+⇌ H2R ⇌ HR–⇌ R2–. The dissociation constants in water and 50 mass % aqueous ethanol were obtained in buffer solutions of diluted HCl using the spectrophotometric method accompanied by a potentiometric determination of pH at an ionic strength of 0.05 M and 25.0 ± 1 °C. The dye concentrations in the working solutions were, as a rule, within the range of (5–10)×10–6 M. The thermodynamic values of the dissociation constants were calculated using the Debye–Hückel equation, the second approach, for ionic activity coefficients. The absorption spectra in the visible region of the individual molecular and ionic forms were determined for the above-mentioned compounds and the ester of 3'-nitrofluorescein. For the last, the dissociation constants were determined in aqueous ethanol. Whereas in water the fraction of the zwitterionic tautomer of nitro­fluoresceins increases as compared with the parent compound, in aqueous ethanol, the colorless lactone predominates. The microscopic dissociation constants were determined and their values are in line with the influence of the electrophilic nitro group. The alkaline hydro­lysis of the nitrofluorescein diacetates was investigated in the two aforementioned solvents. The obtained results allowed us to single out the rate constants of the two-step kinetics of the hydrolysis of the diacetyl derivatives of nitrofluoresceins. V.I.Vernadsky Institute of General and Inorganic Chemistry 2024-10-25 Article Article Physical chemistry Физическая xимия Фізична xімія application/pdf https://ucj.org.ua/index.php/journal/article/view/687 10.33609/2708-129X.90.9.2024.3-18 Ukrainian Chemistry Journal; Vol. 90 No. 9 (2024): Ukrainian Chemistry Journal; 3-18 Украинский химический журнал; Том 90 № 9 (2024): Ukrainian Chemistry Journal; 3-18 Український хімічний журнал; Том 90 № 9 (2024): Ukrainian Chemistry Journal; 3-18 2708-129X 2708-1281 en https://ucj.org.ua/index.php/journal/article/view/687/341
institution Ukrainian Chemistry Journal
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datestamp_date 2025-03-21T18:56:14Z
collection OJS
language English
topic_facet Nitrofluorescein
acid-base dissociation
water-ethanol binary solvent
absorption spectra
dissociation constants
tautomerism
diacetylfluorescein
two-step alkaline hyd­ro­lysis
rate constants.
format Article
author Kharchenko, Daria
Shekhovtsov, Sergiy
Cheipesh, Tetiana
Mchedlov-Petrossyan, Mykola
spellingShingle Kharchenko, Daria
Shekhovtsov, Sergiy
Cheipesh, Tetiana
Mchedlov-Petrossyan, Mykola
MONONITROFLUORESCEINS IN AQUEOUS MEDIA: ACID-BASE EQUILIBRIA, TAUTOMERISM, AND HYDROLYSIS OF DIACETATES
author_facet Kharchenko, Daria
Shekhovtsov, Sergiy
Cheipesh, Tetiana
Mchedlov-Petrossyan, Mykola
author_sort Kharchenko, Daria
title MONONITROFLUORESCEINS IN AQUEOUS MEDIA: ACID-BASE EQUILIBRIA, TAUTOMERISM, AND HYDROLYSIS OF DIACETATES
title_short MONONITROFLUORESCEINS IN AQUEOUS MEDIA: ACID-BASE EQUILIBRIA, TAUTOMERISM, AND HYDROLYSIS OF DIACETATES
title_full MONONITROFLUORESCEINS IN AQUEOUS MEDIA: ACID-BASE EQUILIBRIA, TAUTOMERISM, AND HYDROLYSIS OF DIACETATES
title_fullStr MONONITROFLUORESCEINS IN AQUEOUS MEDIA: ACID-BASE EQUILIBRIA, TAUTOMERISM, AND HYDROLYSIS OF DIACETATES
title_full_unstemmed MONONITROFLUORESCEINS IN AQUEOUS MEDIA: ACID-BASE EQUILIBRIA, TAUTOMERISM, AND HYDROLYSIS OF DIACETATES
title_sort mononitrofluoresceins in aqueous media: acid-base equilibria, tautomerism, and hydrolysis of diacetates
description This article reports equilibrium and kinetic data for three fluorescein dyes containing the nitro group in the residue of the phthalic acid, 3'-, 4'-, and 5'-nitrofluorescein, in water and 50 mass % aqueous ethanol. These compounds, particularly the recently synthesized 3'-nitrofluorescein, were less considered polyprotic acids than many other fluorescein dyes. The dyes behave as diprotic acids, which can also be protonated: H3R+⇌ H2R ⇌ HR–⇌ R2–. The dissociation constants in water and 50 mass % aqueous ethanol were obtained in buffer solutions of diluted HCl using the spectrophotometric method accompanied by a potentiometric determination of pH at an ionic strength of 0.05 M and 25.0 ± 1 °C. The dye concentrations in the working solutions were, as a rule, within the range of (5–10)×10–6 M. The thermodynamic values of the dissociation constants were calculated using the Debye–Hückel equation, the second approach, for ionic activity coefficients. The absorption spectra in the visible region of the individual molecular and ionic forms were determined for the above-mentioned compounds and the ester of 3'-nitrofluorescein. For the last, the dissociation constants were determined in aqueous ethanol. Whereas in water the fraction of the zwitterionic tautomer of nitro­fluoresceins increases as compared with the parent compound, in aqueous ethanol, the colorless lactone predominates. The microscopic dissociation constants were determined and their values are in line with the influence of the electrophilic nitro group. The alkaline hydro­lysis of the nitrofluorescein diacetates was investigated in the two aforementioned solvents. The obtained results allowed us to single out the rate constants of the two-step kinetics of the hydrolysis of the diacetyl derivatives of nitrofluoresceins.
publisher V.I.Vernadsky Institute of General and Inorganic Chemistry
publishDate 2024
url https://ucj.org.ua/index.php/journal/article/view/687
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AT cheipeshtetiana mononitrofluoresceinsinaqueousmediaacidbaseequilibriatautomerismandhydrolysisofdiacetates
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last_indexed 2025-09-24T17:43:58Z
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