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Protonation

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Protonation - Free Register to Access Experts & Abstracts

Silvio Sammartano - One of the best experts on this subject based on the ideXlab platform.

  • polyacrylates in aqueous solution the dependence of Protonation on molecular weight ionic medium and ionic strength
    Reactive & Functional Polymers, 2003
    Co-Authors: Concetta De Stefano, Antonio Gianguzza, Daniela Piazzese, Silvio Sammartano
    Abstract:

    Abstract The Protonation constants of polyacrylates with different molecular weights ( W =2000–750 000 Da) were determined in different ionic media (alkali metal chlorides and nitrates, tetraalkylammonium chlorides), at 25 °C, by potentiometric measurements (H + –glass electrode). Literature data were also considered. Different models used to analyse Protonation data were compared: the first was the modified Henderson–Hasselbalch two-parameter equation, and the second was the three-parameter equation proposed by Hogfeldt. The dependence on the ionic strength of the different supporting electrolytes and all the Protonation parameters involved in the two models showed the trend Et 4 N + ≫Li + >Na + ≥K + , in accordance with the tendencies of these cations to interact with polycarboxylates. The dependence on molecular weight shows a slightly increasing effect with N (number of monomer units in the polyelectrolyte). Empirical relationships were found for the dependence of the Protonation parameters on both ionic strength (I/mol l −1 ) and N. The use of Protonation data was considered for polyacrylates in speciation studies, and specific interaction parameters were calculated according to the SIT (Specific Ion Interaction Theory) model.

  • speciation of phytate ion in aqueous solution Protonation constants in tetraethylammonium iodide and sodium chloride
    Journal of Chemical & Engineering Data, 2003
    Co-Authors: Concetta De Stefano, And Demetrio Milea, Silvio Sammartano
    Abstract:

    Acid−base properties of phytic acid [1,2,3,4,5,6-hexakis(dihydrogen phosphate)-myo-inositol] in aqueous solution have been studied, by potentiometric measurements ([H+]-glass electrode), in tetraethylammonium iodide (Et4NI) and sodium chloride aqueous media, at different ionic strengths (0 < I mol L-1 ≤ 1 for Et4NI and 0 < I mol L-1 ≤ 5 for NaCl) and at t = 25 °C. Protonation of phytate ion proved strongly dependent on both ionic medium and ionic strength. The Protonation constants obtained in NaCl are considerably lower than the corresponding ones in Et4NI (e.g., at I = 0.5 mol·L-1, log = 11.7 and 9.1 in Et4NI and in NaCl, respectively), owing to the strong interactions occurring between phytate and sodium cations present in the background salt. Some empirical equations are proposed for the dependence of Protonation constants on ionic strength for both ionic media. Also, the function log versus i (i = Protonation step) can be modeled, and this allowed us to guess some Protonation constants (in Et4NI) at ...

  • salt effects on the Protonation of oxalate in aqueous nacl kcl and tetraethylammonium iodide solution at 5 t 50 c and 0 i 1 mol dm 3
    Thermochimica Acta, 1992
    Co-Authors: Alessandro De Robertis, Concetta De Stefano, Carmelo Rigano, Silvio Sammartano
    Abstract:

    Abstract Protonation constants of oxalate (ox 2- ) were obtained, by potentiometric measurements, in NaCl, KCl and tetraethylammonium iodide aqueous solutions in the ranges 5 ⩽ T ⩽ 50°C and 0 ⩽ I ⩽ 1 mol dm −3 . The differences in Protonation constant values were explained by a complex formation model assuming the formation of M(ox) − and MH(ox) 0 (M = Na + K + ) complexes. From the dependence on temperature of the Protonation and formation constants, Δ H ° values were calculated. The dependence on ionic strength of the formation thermodynamic parameters was obtained for each species. Consideration is given to the use of different concentration scales, and comparison is made with literature findings. Recommended values are given. Simulated Protonation constants in sea water conditions are reported.

Concetta De Stefano - One of the best experts on this subject based on the ideXlab platform.

  • polyacrylates in aqueous solution the dependence of Protonation on molecular weight ionic medium and ionic strength
    Reactive & Functional Polymers, 2003
    Co-Authors: Concetta De Stefano, Antonio Gianguzza, Daniela Piazzese, Silvio Sammartano
    Abstract:

    Abstract The Protonation constants of polyacrylates with different molecular weights ( W =2000–750 000 Da) were determined in different ionic media (alkali metal chlorides and nitrates, tetraalkylammonium chlorides), at 25 °C, by potentiometric measurements (H + –glass electrode). Literature data were also considered. Different models used to analyse Protonation data were compared: the first was the modified Henderson–Hasselbalch two-parameter equation, and the second was the three-parameter equation proposed by Hogfeldt. The dependence on the ionic strength of the different supporting electrolytes and all the Protonation parameters involved in the two models showed the trend Et 4 N + ≫Li + >Na + ≥K + , in accordance with the tendencies of these cations to interact with polycarboxylates. The dependence on molecular weight shows a slightly increasing effect with N (number of monomer units in the polyelectrolyte). Empirical relationships were found for the dependence of the Protonation parameters on both ionic strength (I/mol l −1 ) and N. The use of Protonation data was considered for polyacrylates in speciation studies, and specific interaction parameters were calculated according to the SIT (Specific Ion Interaction Theory) model.

  • speciation of phytate ion in aqueous solution Protonation constants in tetraethylammonium iodide and sodium chloride
    Journal of Chemical & Engineering Data, 2003
    Co-Authors: Concetta De Stefano, And Demetrio Milea, Silvio Sammartano
    Abstract:

    Acid−base properties of phytic acid [1,2,3,4,5,6-hexakis(dihydrogen phosphate)-myo-inositol] in aqueous solution have been studied, by potentiometric measurements ([H+]-glass electrode), in tetraethylammonium iodide (Et4NI) and sodium chloride aqueous media, at different ionic strengths (0 < I mol L-1 ≤ 1 for Et4NI and 0 < I mol L-1 ≤ 5 for NaCl) and at t = 25 °C. Protonation of phytate ion proved strongly dependent on both ionic medium and ionic strength. The Protonation constants obtained in NaCl are considerably lower than the corresponding ones in Et4NI (e.g., at I = 0.5 mol·L-1, log = 11.7 and 9.1 in Et4NI and in NaCl, respectively), owing to the strong interactions occurring between phytate and sodium cations present in the background salt. Some empirical equations are proposed for the dependence of Protonation constants on ionic strength for both ionic media. Also, the function log versus i (i = Protonation step) can be modeled, and this allowed us to guess some Protonation constants (in Et4NI) at ...

  • salt effects on the Protonation of oxalate in aqueous nacl kcl and tetraethylammonium iodide solution at 5 t 50 c and 0 i 1 mol dm 3
    Thermochimica Acta, 1992
    Co-Authors: Alessandro De Robertis, Concetta De Stefano, Carmelo Rigano, Silvio Sammartano
    Abstract:

    Abstract Protonation constants of oxalate (ox 2- ) were obtained, by potentiometric measurements, in NaCl, KCl and tetraethylammonium iodide aqueous solutions in the ranges 5 ⩽ T ⩽ 50°C and 0 ⩽ I ⩽ 1 mol dm −3 . The differences in Protonation constant values were explained by a complex formation model assuming the formation of M(ox) − and MH(ox) 0 (M = Na + K + ) complexes. From the dependence on temperature of the Protonation and formation constants, Δ H ° values were calculated. The dependence on ionic strength of the formation thermodynamic parameters was obtained for each species. Consideration is given to the use of different concentration scales, and comparison is made with literature findings. Recommended values are given. Simulated Protonation constants in sea water conditions are reported.

Cemil Öğretir - One of the best experts on this subject based on the ideXlab platform.

  • Spectroscopic Determination of Acid Dissociation Constants of Some Novel Drug Precursor 6-Acylbenzothiazolon Derivatives
    Journal of Chemical & Engineering Data, 2010
    Co-Authors: Yadigar Gulseven Sidir, Isa Sidir, Halil Berber, Erol Taşal, Cemil Öğretir
    Abstract:

    The acid dissociation constants, as pKa values, of eight drug precursor 6-acylbenzothiazolon derivatives were determined using UV−vis spectroscopic technique. The Protonation and deProtonation behaviors of the investigated molecules were studied from super basic to super acid regions (i.e., 8 mol·L−1 KOH to 98 % H2SO4) including the pH region. It was observed that Protonation occurs only at the amid group in the super acid region. By validating the obtained acid dissociation constants, elucidation of the structure and Protonation mechanisms of the studied molecules was attempted.

  • Spectroscopic Determination of Acidity Constants of Some Monoazo Resorcinol Derivatives
    Journal of Chemical & Engineering Data, 2008
    Co-Authors: Halil Berber, Cemil Öğretir, Emine Cigdem Sev Lekesiz, Emel Ermiş
    Abstract:

    The acidity constants, as pKa values, of six monoazo resorcinol derivatives were determined by the UV–visible spectroscopic technique at 25 °C (± 0.1 °C). The Protonation and deProtonation behaviors of the studied molecules were studied from the super basic to the super acid region (i.e., 10 N NaOH to 98 % H2SO4) including the pH region. It was observed that deProtonation occurs at the resorcinol ring. The first Protonation occurs at the nitrogen atom next to the resorcinol ring, whereas the second Protonation occurs at the nitrogen atom next to the phenyl ring.

  • Determination and Evaluation of Acid Dissociation Constants of Some Substituted 2-Aminobenzothiazole Derivatives
    Journal of Chemical & Engineering Data, 2008
    Co-Authors: Cemil Öğretir, Şeref Demirayak, N. Funda Tay, Murat Duran
    Abstract:

    The acid dissociation constants of some 4- and/or 6-substituted 2-aminobenzothiazole and 4-substituted thiazole derivatives were determined spectroscopically. With the exception of a few, the first Protonation was found to occur on the amino group. In some molecules where prototropic tautomerism is possible, a change-over in the Protonation mechanism was observed. The first Protonation under these circumstances was found to occur on the imino nitrogen atom. The second Protonation takes place on the thiazole ring nitrogen atom.

Halil Berber - One of the best experts on this subject based on the ideXlab platform.

  • Acidity constant determination of novel drug precursor benzothiazolon derivatives including acyl and piperazine moieties
    Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2013
    Co-Authors: Isa Sidir, Yadigar Gulseven Sidir, Halil Berber
    Abstract:

    In this study, Protonation and deProtonation behaviors of eight new drug precursor benzothiazolon derivatives in all of acidic and basic scale (super acidic, pH, super basic regions) are analyzed by using UV–visible spectrophotometric technique. Acidity constants (pKa), elucidation of the structure and Protonation mechanisms of the studied molecules are obtained. Substituent effect on acidity constant values is discussed. These molecules are protonated from oxygen atom of acetamide group in the keto form. The Protonation is found to be considerably contributed by the keto form.

  • Spectroscopic Determination of Acid Dissociation Constants of Some Novel Drug Precursor 6-Acylbenzothiazolon Derivatives
    Journal of Chemical & Engineering Data, 2010
    Co-Authors: Yadigar Gulseven Sidir, Isa Sidir, Halil Berber, Erol Taşal, Cemil Öğretir
    Abstract:

    The acid dissociation constants, as pKa values, of eight drug precursor 6-acylbenzothiazolon derivatives were determined using UV−vis spectroscopic technique. The Protonation and deProtonation behaviors of the investigated molecules were studied from super basic to super acid regions (i.e., 8 mol·L−1 KOH to 98 % H2SO4) including the pH region. It was observed that Protonation occurs only at the amid group in the super acid region. By validating the obtained acid dissociation constants, elucidation of the structure and Protonation mechanisms of the studied molecules was attempted.

  • Spectroscopic Determination of Acidity Constants of Some Monoazo Resorcinol Derivatives
    Journal of Chemical & Engineering Data, 2008
    Co-Authors: Halil Berber, Cemil Öğretir, Emine Cigdem Sev Lekesiz, Emel Ermiş
    Abstract:

    The acidity constants, as pKa values, of six monoazo resorcinol derivatives were determined by the UV–visible spectroscopic technique at 25 °C (± 0.1 °C). The Protonation and deProtonation behaviors of the studied molecules were studied from the super basic to the super acid region (i.e., 10 N NaOH to 98 % H2SO4) including the pH region. It was observed that deProtonation occurs at the resorcinol ring. The first Protonation occurs at the nitrogen atom next to the resorcinol ring, whereas the second Protonation occurs at the nitrogen atom next to the phenyl ring.

Guy Bouchoux - One of the best experts on this subject based on the ideXlab platform.

  • Gas-phase Protonation thermochemistry of adenosine.
    Journal of Physical Chemistry B, 2008
    Co-Authors: David Touboul, Guy Bouchoux, Renato Zenobi
    Abstract:

    The goal of this work was to obtain a detailed insight on the gas-phase Protonation energetic of adenosine using both mass spectrometric experiments and quantum chemical calculations. The experimental approach used the extended kinetic method with nanoelectrospray ionization and collision-induced dissociation tandem mass spectrometry. This method provides experimental values for proton affinity, PA(adenosine) = 979 +/- 1 kJ.mol (-1), and for the "Protonation entropy", Delta p S degrees (adenosine) = S degrees (adenosineH +) - S degrees (adenosine) = -5 +/- 5 J.mol (-1).K (-1). The corresponding gas-phase basicity is consequently equal to: GB(adenosine) = 945 +/- 2 kJ.mol (-1) at 298K. Theoretical calculations conducted at the B3LYP/6-311+G(3df,2p)//B3LYP/6-31+G(d,p) level, including 298 K enthalpy correction, predict a proton affinity value of 974 kJ.mol (-1) after consideration of isodesmic proton transfer reactions with pyridine as the reference base. Moreover, computations clearly showed that N3 is the most favorable Protonation site for adenosine, due to a strong internal hydrogen bond involving the hydroxyl group at the 2' position of the ribose sugar moiety, unlike observations for adenine and 2'-deoxyadenosine, where Protonation occurs on N1. The existence of negligible Protonation entropy is confirmed by calculations (theoretical Delta p S degrees (adenosine) approximately -2/-3 J.mol (-1).K (-1)) including conformational analysis and entropy of hindered rotations. Thus, the calculated Protonation thermochemical properties are in good agreement with our experimental measurements. It may be noted that the new PA value is approximately 10 kJ.mol (-1) lower than the one reported in the National Institute of Standards and Technology (NIST) database, thus pointing to a correction of the tabulated Protonation thermochemistry of adenosine.

  • Gas phase Protonation of α, β and γ-dicarbonyls: Thermochemistry and structures
    International Journal of Mass Spectrometry, 2007
    Co-Authors: Aliouane Akrour, Zohra Chikh, Fayçal Djazi, Mostapha Elbannay, Florence Berruyer, Guy Bouchoux
    Abstract:

    Abstract An experimental and theoretical study of the Protonation of representative dicarbonyl compounds M = 2,3-butanedione (biacetyl), 1 , 2,4-pentanedione (acetylacetone), 2 , 2,5-hexanedione (acetonylacetone), 3 , and methyl-acetoacetate, 4 has been carried out. The experimental proton affinities and Protonation entropies have been obtained by the extended kinetic method using the orthogonal distance regression (ODR) treatment. Theoretical proton affinities are calculated at the G2MP2 level of theory while Protonation entropies were estimated after a detailed treatment of the internal rotations. The data show that Protonation of 1 and 2 is associated with negligible Protonation entropies while significant negative values are obtained for molecules 3 and 4 . Protonation of 2,3-butanedione, 1a , is associated with a tautomerisation inside the proton transfer complex thus leading to protonated 2-hydroxy-butenone, 1bH + . Protonation thermochemistry of 2,4-pentanedione 2 may be simply rationalized by the Protonation of its most stable tautomer, the 4-hydroxy-3-pentene-2-one, 2b , to give its most stable protonated form 2bH + stabilized by a strong intramolecular hydrogen bond. Protonation of 2,5-hexanedione 3a most probably produces a cyclic structure stabilized by a covalent bonding, 3aHc + . The structure of neutral methyl acetoacetate 4 sampled during Protonation in mass spectrometry experiments appears to be its diketonic form 4a ; its Protonation leading to an internally hydrogen bonded stabilized structure 4aH + .

  • Gas-phase basicities of polyfunctional molecules. Part 1: Theory and methods.
    Mass Spectrometry Reviews, 2007
    Co-Authors: Guy Bouchoux
    Abstract:

    The experimental and theoretical methods of determination of gas-phase basicities, proton affinities and Protonation entropies are presented in a tutorial form. Particularities and limitations of these methods when applied to polyfunctional molecules are emphasized. Structural effects during the Protonation process in the gas-phase and their consequences on the corresponding thermochemistry are reviewed and classified. The role of the nature of the basic site (Protonation on non-bonded electron pairs or on pi-electron systems) and of substituent effects (electrostatic and resonance) are first examined. Then, linear correlations observed between gas-phase basicities and ionization energies or substituent constants are recalled. Hydrogen bonding plays a special part in proton transfer reactions and in the Protonation characteristics of polyfunctional molecules. A survey of the main properties of intermolecular and intramolecular hydrogen bonding in both neutral and protonated species is proposed. Consequences on the Protonation thermochemistry, particularly of polyfunctional molecules are discussed. Finally, chemical reactions which may potentially occur inside protonated clusters during the measurement of gas-phase basicities or inside a protonated polyfunctional molecule is examined. Examples of bond dissociations with hydride or alkyl migrations, proton transport catalysis, tautomerization, cyclization, ring opening and nucleophilic substitution are presented to illustrate the potentially complex chemistry that may accompany the Protonation of polyfunctional molecules.

  • Structural and energetic aspects of the Protonation of phenol, catechol, resorcinol, and hydroquinone.
    Chemistry - A European Journal, 2002
    Co-Authors: Guy Bouchoux, Dirk Defaye, T. Mcmahon, A. Likholyot, M. Yáñez
    Abstract:

    The various protonated forms of phenol (1), catechol (2), resorcinol (3), and hydroquinone (4) were explored by ab initio quantum chemical calculations at the MP2/6-31G(d) and B3LYP/6-31G(d) levels. Proton affinities (PA) of 1-4 were calculated by the combined G2(MP2,SVP) method, and their gas-phase basicities were estimated after calculation of the change in entropy on Protonation. These theoretical data were compared with the corresponding experimental values determined in a high-pressure mass spectrometer. This comparison confirmed that phenols are essentially carbon bases and that Protonation generally occurs in a position para to the hydroxyl group. Resorcinol is the most effective base (PA = 856 kJ mol-1) due to the participation of both oxygen atoms in the stabilization of the protonated form. Since Protonation is accompanied by a freezing of the two internal rotations, a significant decrease in entropy is observed. The basicity of catechol (PA = 823 kJ mol-1) is due to the existence of an intramolecular hydrogen bond, which is strengthened upon Protonation. The lower basicity of hydroquinone (PA = 808 kJ mol-1) is a consequence of the fact that Protonation necessarily occurs in a position ortho to the hydroxyl group. When the previously published data are reconsidered and a corrected Protonation entropy is used, a proton affinity value of 820 kJ mol-1 is obtained for phenol.