THERMODYNAMIC THEORY OF ACID DISSOCIATION OF METHYL SUBSTITUTED PHENOLS IN AQUEOUS SOLUTION

1961 ◽  
Vol 65 (5) ◽  
pp. 811-814 ◽  
Author(s):  
L. G. Hepler ◽  
W. F. O'Hara
Keyword(s):  
Aqueous Solution ◽  
Thermodynamic Theory ◽  
Acid Dissociation ◽  
Substituted Phenols

Inline Raman Spectroscopy and Indirect Hard Modeling for Concentration Monitoring of Dissociated Acid Species

2020 ◽  
pp. 000370282097327
Author(s):  
Alexander Echtermeyer ◽  
Caroline Marks ◽  
Alexander Mitsos ◽  
Jörn Viell
Keyword(s):  
Aqueous Solution ◽  
Raman Spectroscopy ◽  
Process Analytical Technology ◽  
Dissociation Constants ◽  
A Priori ◽  
Calibration Procedure ◽  
Acid Dissociation ◽  
Multivariate Curve Resolution ◽  
Least Squares Regression ◽  
Fitting Ideal

We propose an approach for monitoring the concentration of dissociated carboxylic acid species in dilute aqueous solution. The dissociated acid species are quantified employing inline Raman spectroscopy in combination with indirect hard modeling (IHM) and multivariate curve resolution (MCR). We introduce two different titration-based hard model (HM) calibration procedures for a single mono- or polyprotic acid in water with well-known (method A) or unknown (method B) acid dissociation constants p Ka. In both methods, spectra of only one acid species in water are prepared for each acid species. These spectra are used for the construction of HMs. For method A, the HMs are calibrated with calculated ideal dissociation equilibria. For method B, we estimate p Ka values by fitting ideal acid dissociation equilibria to acid peak areas that are obtained from a spectral HM. The HM in turn is constructed on the basis of MCR data. Thus, method B on the basis of IHM is independent of a priori known p K a values, but instead provides them as part of the calibration procedure. As a detailed example, we analyze itaconic acid in aqueous solution. For all acid species and water, we obtain low HM errors of < 2.87 × 10−4mol mol−1 in the cases of both methods A and B. With only four calibration samples, IHM yields more accurate results than partial least squares regression. Furthermore, we apply our approach to formic, acetic, and citric acid in water, thereby verifying its generalizability as a process analytical technology for quantitative monitoring of processes containing carboxylic acids.

Ligand substitution reactions of pentacyanoferrate(II) complexes with N-heterocyclic cations in aqueous solution

1989 ◽  
Vol 67 (11) ◽  
pp. 1774-1779 ◽  
Author(s):  
Donal Hugh Macartney ◽  
Lauren Jean Warrack
Keyword(s):  
Aqueous Solution ◽  
Rate Constants ◽  
Dissociation Constants ◽  
Formation Rate ◽  
Spectroscopic Studies ◽  
Ligand Substitution ◽  
Acid Dissociation ◽  
Specific Rate ◽  
Dissociative Mechanism ◽  
Heterocyclic Cations

Kinetic and spectroscopic studies have been carried out in aqueous solution on the formation (from Fe(CN)5OH23−) and dissociation of pentacyanoferrate(II) complexes containing 1-(4-pyridyl)pyridinium and the neutral, protonated, and N-methylated forms of 4,4′-bipyridine (BPY), 1,2-bis(4-pyridyl)ethane (BPA), and trans-1,2-bis(4-pyridyl)ethylene (BPE). The pH dependences of the formation kinetics have been analyzed in terms of the specific rate and acid dissociation constants for these ligands. The rate constants (25.0 °C, I = 0.10 M) for the formation of the dinuclear complexes (NC)5FeLFe(CN)56− have been determined for BPY (50 M−1 s−1), BPA (66 M−1 s−1), BPE (95 M−1 s−1), and pyrazine (10 M−1 s−1), and are compared with the respective rate constants for the formation of (NC)5FeLCo(NH3)5. The relationships between the formation rate constants and the size of the ligand, the number of donor sites, and the magnitude and position of charges on the ligand are discussed in terms of an ion-pair dissociative mechanism. Keywords: pentacyanoferrate(II) complexes, N-heterocycles, ligand substitution, kinetics.

Equilibrium studies on lithium(I) transfer into ionic liquid with a water-soluble octabromoporphyrin (H2(OBTMPyP)4+) from aqueous phase

2009 ◽  
Vol 13 (08n09) ◽  
pp. 849-853 ◽  
Author(s):  
Takuya Shimomura ◽  
Masaaki Tabata ◽  
Jun Nishimoto
Keyword(s):  
Aqueous Solution ◽  
Ionic Liquid ◽  
Ion Exchange ◽  
Dissociation Constants ◽  
Equilibrium Constants ◽  
Water Soluble ◽  
Acid Dissociation ◽  
Acid Dissociation Constants ◽  
Equilibrium Studies ◽  
Counter Ions

A water-soluble octabromoporphyrin 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (H2(OBTMPyP)4+), H2P4+) and its lithium complex, Li(OBTMPyP)3+ , (LiP3+) , transferred quantitatively to an ionic liquid (IL), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM+PF6-) with no addition of other counter ions. The acid-dissociation constants of H2(OBTMPyP)4+ between aqueous and BMIM+PF6- phases were determined spectrophotometrically and found to be 10-7.67 and 10-11.33 at I = 0.1 for K a1,IL = [H+]aq[HP3+]IL/[H2P4+]IL and K a2,IL = [H+]aq[P2+]IL/[HP3+]IL , respectively. Since the acid-dissociation constants involve the partition of H2(OBTMPyP)4+ between aqueous and IL phases, the determined values are ten times as low as those observed in aqueous solution. The transfer equilibrium constants of LiP3+ and NaP3+ to IL defined by K MP,IL = [MP3+]IL/[M+]aq[P2+]IL (M = Li+ or Na+) were found to be 104.83 and 101.31 for K LiP,IL and KNaP,IL , respectively. LiP3+ transferred selectively in the presence of Na+ (K LiP,IL /K NaP,IL = 103.52) to IL phase through an ion-exchange mechanism between BMIM+PF6- and Li(OBTMPyP)3+ .

Reactions of p-Substituted Phenols with Nitrous Acid in Aqueous Solution

2013 ◽  
Vol 46 (3) ◽  
pp. 143-150 ◽  
Author(s):  
María A. Rubio ◽  
Eduardo Lissi ◽  
Nicol Olivera ◽  
Jael L. Reyes ◽  
Camilo López-Alarcon
Keyword(s):  
Aqueous Solution ◽  
Nitrous Acid ◽  
Substituted Phenols
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