Who knows the Ka values of water and the hydronium ion?

Starkey, Ronald; Norman, Jack; Hintze, Mark

doi:10.1021/ed063p473

Cited by 18 publications

(17 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1,2 Similarly, he cited both "rational" and "conventional" pK a 's for aqueous H + (−1.74 and 0.00, respectively). In this Journal, the issue of these two different pairs of pK a values was first raised in 1986 by Starkey et al, 3 who cited a seminal 1960 paper in J. Am.…”

Section: Two Different Pk a Values For Watermentioning

confidence: 75%

“…Brønsted himself was inconsistent in his use of the rational versus conventional p K a values. He stated clearly that, for solute acids, the “conventional” K a with its water activity of 1 was preferred . However, for the solvent water, Brønsted usually defaulted to the “rational” K a ′ values for H 2 O and H 3 O + . , …”

Section: Discussionmentioning

confidence: 99%

“…In his 1928 discussion of the p K a of H 2 O, Brønsted distinguished 15.74, the “rational” value, from 14.00, the “conventional” value. , Similarly, he cited both “rational” and “conventional” p K a ’s for aqueous H + (−1.74 and 0.00, respectively). In this Journal , the issue of these two different pairs of p K a values was first raised in 1986 by Starkey et al, who cited a seminal 1960 paper in J. Am.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

pK_a Values in the Undergraduate Curriculum: What Is the Real pK_a of Water?

Silverstein

Heller

2017

J. Chem. Educ.

View full text Add to dashboard Cite

Since at least the 1960s, organic chemistry textbooks have featured pK a tables for organic acids that include values for H2O and H3O+ (15.74 and −1.74, respectively) that are thermodynamically and chemically indefensible. Here we trace this error back to Brønsted’s early contributions in the 1920s to the Brønsted–Lowry Theory of acids and bases. Organic chemists generally defend the use of these values by citing measurements of the equilibrium constant for the water + methoxide acid–base reaction that suggested that methanol (pK a = 15.54) is a stronger acid than water; from this, organic chemists have concluded that pK a of water must be 15.74 rather than 14.00. Here we discuss the problems that invalidate this conclusion, the most important being that it is based on the use of the pure liquid standard state (mole fraction = 1) that is quite different from the standard state for acidities determined in dilute solution (molality = 1). Using the latter standard state, the equilibrium constant for the water/methoxide reaction ranges from 4 to 70, showing water to be a stronger acid than methanol, and justifying the use of the thermodynamically correct value, pK a(H2O) = 14.00.

show abstract

Section: Two Different Pk a Values For Watermentioning

confidence: 75%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

pK_a Values in the Undergraduate Curriculum: What Is the Real pK_a of Water?

Silverstein

Heller

2017

J. Chem. Educ.

View full text Add to dashboard Cite

show abstract

“…The difference between the effects of H 2 O and toluene originate from the bond structure of these two molecules: the H 2 O molecule has O−H bond that can release and accept H atom as a proton, whereas the toluene has a covalent C−H bond that does not easily release H atoms. The pK a of H 2 O is 15.7, 30 whereas that of toluene is 41.0, 31 which shows the significant difference between these two solvent molecules. Moreover, the TS with toluene should be located in the organic phase, which should strongly destabilize the hydrophilic hydroxyl group, providing extremely high activation barrier for this case.…”

Section: Resultsmentioning

confidence: 94%

Spectroscopic and Computational Analyses of Liquid–Liquid Interfacial Reaction Mechanism of Boric Acid Esterification with 2,2,4-Trimethyl-1,3-pentanediol in Boron Extraction Processes

Kunimoto

Bothe

Tamura³

et al. 2018

J. Phys. Chem. C

View full text Add to dashboard Cite

Purification of silica solution to chemically remove impurities is a novel approach for preparing solar-grade Si. Complete elimination of boron is necessary, as it significantly affects the semiconductor properties of Si if included. To build an efficient reactor for boron extraction, the mechanism of extraction reaction based on molecular behavior should be well understood. Here, we investigated the liquid−liquid extraction of boron (boric-acid) using 2,2,4-trimethyl-1,3-pentanediol as an extractant, which takes place at the liquid−liquid interface experimentally and theoretically. Raman spectroscopy for the microflow reactor provided the concentration of boric acid after extraction, whereas density functional theory calculation showed the reaction energy profiles of the underlying chemical reactions. Calculation results suggested that H 2 O molecules from the aqueous phase promote extraction by enabling the formation of [BOH-HOH-HOC], a sufficiently stable, nonsteric structure, which stabilizes the transition state and facilitates boric acid esterification. Otherwise, this reaction cannot take place in standard conditions. Raman spectroscopy applied to the extraction process in a microflow reactor supported this conclusion experimentally. These results suggest that the extraction reaction at the liquid−liquid interface is mass transfer-limited. This can help the design of effective reactors to eliminate boron impurity from silica solution.

show abstract

“…However, this does not preclude water itself from serving as the (de)protonating medium. The pKa of bulk water is 15.7 which is more than basic enough to deprotonate a zinc bound water (pKa 7.5), whereas the resulting hydronium ion is definitely acidic enough (pKa -1.7) [40] to protonate adjacent waters. Moreover, studies of similar dimetalloproteins and dimetallic enzyme analogs suggest that the pKa of a water molecule bridging zinc ions is lowered to no more than about 5.8 - still two orders of magnitude higher than D108’s acid dissociation constant [41,42].…”

Section: Resultsmentioning

confidence: 99%

New Insights into the Binding and Catalytic Mechanisms of Bacillus thuringiensis Lactonase: Insights into B. thuringiensis AiiA Mechanism

2013

View full text Add to dashboard Cite

The lactonase enzyme (AiiA) produced by Bacillus thuringiensis serves to degrade autoinducer-1 (AI-1) signaling molecules in what is an evolved mechanism by which to compete with other bacteria. Bioassays have been previously performed to determine whether the AI-1 aliphatic tail lengths have any effect on AiiA’s bioactivity, however, data to date are conflicting. Additionally, specific residue contributions to the catalytic activity of AiiA provide for some interesting questions. For example, it has been proposed that Y194 serves to provide an oxyanion hole to AI-1 which is curious given the fact the substrate spans two Zn(2+) ions. These ions might conceivably provide enough charge to promote both ligand stability and the carbonyl activation necessary to drive a nucleophilic attack. To investigate these questions, multiple molecular dynamics simulations were performed across a family of seven acylated homoserine lactones (AHL) along with their associated intermediate and product states. Distance analyses and interaction energy analyses were performed to investigate current bioassay data. Our simulations are consistent with experimental studies showing that AiiA degrades AHLs in a tail length independent manner. However, the presence of the tail is required for activity. Also, the putative oxyanion hole function of Y194 toward the substrate is not observed in any of the reactant or product state simulation trajectories, but does seem to show efficacy in stabilizing the intermediate state. Last, we argue through ionization state analyses, that the proton shuttling necessary for catalytic activity might be mediated by both water and substrate-based intra-molecular proton transfer. Based on this argument, an alternate catalytic mechanism is proposed.

show abstract

Who knows the Ka values of water and the hydronium ion?

Cited by 18 publications

References 0 publications

pK_a Values in the Undergraduate Curriculum: What Is the Real pK_a of Water?

pK_a Values in the Undergraduate Curriculum: What Is the Real pK_a of Water?

Spectroscopic and Computational Analyses of Liquid–Liquid Interfacial Reaction Mechanism of Boric Acid Esterification with 2,2,4-Trimethyl-1,3-pentanediol in Boron Extraction Processes

New Insights into the Binding and Catalytic Mechanisms of Bacillus thuringiensis Lactonase: Insights into B. thuringiensis AiiA Mechanism

Contact Info

Product

Resources

About

Who knows the Ka values of water and the hydronium ion?

Cited by 18 publications

References 0 publications

pKa Values in the Undergraduate Curriculum: What Is the Real pKa of Water?

pKa Values in the Undergraduate Curriculum: What Is the Real pKa of Water?

Spectroscopic and Computational Analyses of Liquid–Liquid Interfacial Reaction Mechanism of Boric Acid Esterification with 2,2,4-Trimethyl-1,3-pentanediol in Boron Extraction Processes

New Insights into the Binding and Catalytic Mechanisms of Bacillus thuringiensis Lactonase: Insights into B. thuringiensis AiiA Mechanism

Contact Info

Product

Resources

About

pK_a Values in the Undergraduate Curriculum: What Is the Real pK_a of Water?

pK_a Values in the Undergraduate Curriculum: What Is the Real pK_a of Water?