Acidity-Basicity Data (pKa Values) in Nonaqueous Solvents (and some in water as well)

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The highlighted papers contain large amounts of pKa data (or other information): acids – red, bases – blue, both acids and bases – purple.

Publication

Data

Medium

Method

Description

Available files

Dalton Trans. 2024, 53, 14226

pKaH and GB values

Acetonitrile, gas phase

UV-Vis spectrometry, Computations

Basicity (pKaH values in MeCN and GB values) of a number of phosphane (posphine) bases, including several seminal phosphanes, such as trimethylphosphane, triphenylphosphine, tripyrrolidinophosphane, tris-pentafluorophenylphosphane, etc.

pKaH values of phosphanes in MeCN and GB values (PDF)

Eur. J. Org. Chem. 2023, 26, e202300453

pKaH and GB values

Acetonitrile, THF, gas phase

UV-Vis spectrometry, Computations

Basicity values in MeCN and THF (pKaH values) of a number of phosphane (posphine) bases containing the benziphenoneimine (bpi) moiety.

pKaH values of phosphanes in MeCN and THF (PDF)

Bioorgan. Med. Chem. 2023, 81, 117203

pKa values

MeCN and MeCN : water mixtures

UV-Vis spectrometry

pKa and pKaH values, of different drugs, bioactive and related compounds in acetonitrile-water mixtures and acetonitrile: Hydrochlorthiazide, Ibuprofen, Valsartan, Atenolol, Lidocaine, Mepivacaine, Propranolol, Scopolamine, Nalidixic acid, 3-aminophenol, benzoic acid. The used water-acetonitrile mixtures were meant to be nonpolar media mimicking the cell membrane interior.

pKa and pKaH values, of different drugs, bioactive and related compounds in acetonitrile-water mixtures and acetonitrile (PDF)

Chem. Eur. J. 2022, 29, e202202953

pKa values

Acetonitrile

UV-Vis spectrometry, 31P NMR

pKa values of Singly-linked and Macrocyclic Bisphosphoric Acid catalysts for Asymmetric Phase-transfer and Brønsted-acid Catalysis. It turns out that the linker length has large influence on enantioselectivity but does not influence much the pKa value.

pKa values of Singly-linked and Macrocyclic Bisphosphoric Acid catalysts in MeCN (PDF)

Anal. Chem. 2022, 94, 4059-4064

Biphasic pKa values (pKaow values)

Octanol:Water

UV-Vis spectrometry, 1H NMR, 13C NMR, 31P NMR

Biphasic pKa values (pKaow values) of 35 acids of various structures and chemical properties (mostly lipophilic) – carboxylic acids (benzoic acid, sorbic acid, cinnamic acid, ibuprofen, stearic acid, etc), phenols (pentachlorophenol, pentabromophenol, etc), sulfonamides and sulfonimides, as well as different CH acids – were determined in the 1-octanol:water solvent system. Biphasic pKa value (pKaow value) is measured in biphasic systems of water in equilibrium with a non-miscible organic solvent, in such a way that a(H+) is measured in aqueous phase (where most of H+ ions reside) and the anion/neutral ratio in the organic phase (where most of the neutrals and anions reside, the latter as ion pairs). The directly obtained (apparent) pKaow values depend on concentration. Concentration-independent values were obtained by extrapolating the apparent values to zero concentration using a Debye–Hückel model.

Octanol:water biphasic pKa values (pKaow values ) of 35 acids and extrapolation plot (PDF)

Acc. Chem. Res. 2021, 54, 3108-3123

pKa values (pKaH values), gas-phase basicities

MeCN, THF, gas phase

UV-Vis spectrometry, NMR, Computations

An overview is given on design and synthesis of neutral (uncharged) superbasic molecules that besides high basicity have other desirable properties. Important structural features of superbases are discussed and pKa (pKaH) values in MeCN and THF, as well as gas-phase basicities of around 30 important superbases (amidines, guanidines, proton sponges, phosphazenes, phosphanes, phosphorus ylides, carbodiphosphoranes) are presented.

pKa (pKaH) values in MeCN and THF, as well as gas-phase basicities of around 30 important superbases (PDF)

Eur. J. Org. Chem. 2021, 1407-1419

pKa values

Acetonitrile

UV-Vis spectrometry

pKa values of 231 acids in acetonitrile, ranging from hydrogen iodide (2.8) and indole (32.57) and covering almost 30 orders of magnitude. This is the revised and significantly extended version of our pKa scale of acids in MeCN. The acids have wide structural variety, ranging from common families (phenols, carboxylic acids, sulfonic acids, hydrogen halides) to highly special molecules (chiral BINOL catalysts, bis(benzoxazole-2-yl)methanes, polyfluorinated compunds) and superacids.

Acidity pKa values of 231 acids in acetonitrile (PDF)

J. Am. Chem. Soc. 2020, 142, 15252-15258

pKa values

Acetonitrile

UV-Vis spectrometry

Chiral benzoic acid catalysts are reported that efficiently catalyse enantioselective [4+2] cycloadditions of acetals. The peculiar structure of the acids features covalently linked thiourea sites that stabilize the carboxylate conjugate bases via intramolecular hydrogen bond to the anionic site. This leads to the low pKa values of the acids compared benzoic acids with similar substitution.

Acidities (pKa in MeCN) of the enantioselective carboxylic acid catalysts (PDF)

Angew. Chem. Int. Edit. 2020, 59, 2028-2032

pKa values

Acetonitrile

UV-Vis spectrometry

Chiral carboxylic acid catalysts are reported that provide access to highly enantioenriched dihydropyran products containing a tetrasubstituted stereogenic center. The high acidity of the carboxylic acid catalyst, which exceeds that of the well-known chiral phosphoric acid catalyst TRIP, is largely derived from stabilization of the carboxylate conjugate base through intramolecular anion-binding to a thiourea site.

Acidities (pKa in MeCN) of the enantioselective carboxylic acid catalysts (PDF)

Rapid Commun. Mass. Sp. 2020

Gas-phase acidity values

Gas phase

FT-ICR mass spectrometry

this study, a self-consistent gas-phase acidity scale consisting of 20 superacids was compiled. The scale ranges from 295.4 to 277.1 kcal mol-1 and extends the previously reported scale towards higher acidities. Gas-phase acidities for several important superacids (e.g. triflic acid) were significantly revised.

Gas-phase acidity scale of superacids (PDF)

Eur. J. Org. Chem. 2019, 6735-6748

pKa values (pKaH values)

Acetonitrile, DMSO, THF, Water

UV-Vis spectrophotometry

pKa values (pKaH values) in MeCN, DMSO, THF and water (altogether close to 400 values) for a large number of organic bases representing all main classes (amines, diamines, anilines, pyridines, imidazoles, amidines, phosphazenes, etc). Simple equations are presented for estimating pKaH in DMSO, THF or water on the basis of MeCN pKaH values.

 

This paper adds a large number of new bases (previously scattered among different papers) to the acetonitrile basicity scale, reaching 279 bases altogether and spanning from pKa 1.28 to 33.14. The whole scale was reevaluated taking all (close to 700) measurements into account. As a result, these values can be considered the most reliable MeCN pKa values available. Earlier values (published in 2005) changed slightly (usually by 0.00 .. 0.04 pKa units).

Basicity pKa (pKaH) values of 279 bases in acetonitrile (PDF)

 

Basicity pKa (pKaH) values of selected bases in water, DMSO, MeCN, THF (PDF)             

Int. J. Mass Spec. 2019, 435, 61–68

pKa and GB values

Acetonitrile, gas phase

FT-ICR, UV-Vis spectrophotometry

Gas-phase basicities and MeCN pKa values have been measured for a series of substituted biguanides (bases obtained by extending guanidines with another guanidine moiety). Most of them qualify as superbases. The structures of several biguanides enable formation of efficient intramolecular hydrogen bond (IMHB), which markedly enhances their basicity, especially in the gas phase

Gas-phase basicity and pKa (acetonitrile) Table (incl literature values)

J. Phys. Org. Chem. 2019, 32, e3940

pKa values

Water

19F NMR

Aqueous pKa values of 19 fluorocompounds (fluorinated sulfonamides, 3,5-Bis(trifluoromethyl)phenol, Pentafluorophenol, fluorinated benzoic acids, hexafluoroisopropanol (HFIP), Nonafluoro-tert-butyl alcohol (NFTB), perfluoropinacol, etc) in the pKa range from 3.5 to 10 have been measured with 19F NMR. 19F NMR pKa measurement has several advantages: accurate concentrations not needed, the method is very tolerant to impurities, several compounds can be measured simultaneously, several uncertainty sources cancel out.

Table of 19F NMR aqueous pKa values

Nature Chemistry 2018, 10, 888-894

pKa values

Acetonitrile

UV-Vis spectrophotometry

Extremely efficient strongly acidic organocatalysts for the Mukaiyama aldol reaction working at low ppm to sub-ppm level with excellent yields and enantiomeric selectivity and turnover numbers (TON numbers) of hundreds of thousands.

 

Tetrahedron Letters 2018, 59, 3738-3748

pKa values

MeCN, 1,2-Dichloroethane, DMSO, Water, THF, Heptane, DME

mainly UV-Vis spectrophotometry

This digest paper presents guidance of making maximum use of the available pKa data. Examples: How to estimate a pKa value in a solvent using correlation analysis and data from other solvents? When such correlation analysis is reliable and when not? In which cases acidity or basicity order is directly transferable between solvents?

Table of pKa data of acids and bases in acetonitrile, DMSO, 1,2-DCE, H2O, Tetrahydrofuran, heptane and dimethoxyethane (PDF)

Green Chemistry 2018, 20, 2392-2394

pKa values

Mixtures of water and methanol

Computations, correlations

pKa values of H2O and methanol on mixtures of H2O and methanol are used for discussing the possible mechanisms of the Zemplén transesterification reaction.

 

Chem. Sci. 2017, 8, 6964-6973

pKa values, pHabs values

1,2-dichloroethane, acetonitrile

UV-Vis spectrophotometry

The most comprehensive solvent acidity scale including 87 acids (incl well-known mineral acids, such as HCl, HBr, HI, H2SO4, HNO3, HBF4, CF3SO3H, FSO3H, HClO4, (CF3SO2)2NH (Tf2NH, bis-triflimide) and (C2F5SO2)2NH) and spanning 28 pKa units in 1,2-dichloroethane (DCE) and linked to the unified acidity scale (pHabs) in an unprecedented and generalized approach only based on experimental values. This enables future measurements of acid strengths (especially of very strong acids) and acidity adjustments in low polarity solvents.

Table of pKa values of the acids in 1,2-dichloroethane as well as the pHabs values of the respective buffer systems, directly comparable to the pH scale in water (PDF)

Angew. Chem. Int. Ed. 2017, 56, 1411–1415

pKa values

(Acidity)

1,2-dichloroethane, acetonitrile

UV-Vis spectrophotometry

1,1,3,3-Tetratrifylpropene (TTP) is proposed as

a highly acidic, allylic C–H acid for Brønsted and Lewis acid catalysis. Its acidity was measured in 1,2-dichloroethane and was compared to that of 1,1,3,3-Tetratrifylpropane, Tf2NH and Tf3CH. On the basis of correlation analysis the estimate of pKa of TPP in MeCN is -2.8.

 

Eur. J. Org. Chem. 2017, 4475–4489

pKa values (basicity)

Acetonitrile, H2O

UV-Vis spectrophotometry

58 previously unpublished basicity values in different media for 39 basic heterocycles (pyridine, quinoline, isoquinoline, imidazole, benzimidazole, phenanthroline, etc) are presented, including 30 experimentally determined pKa values in acetonitrile, as well as a number of pKa values in water. The trends in basicity are rationalized

by comparing the basicity data of related compounds in different solvents, as well as by using isodesmic reactions.

Table of pKa values in MeCN and H2O, as well as gas-phase basicity values (PDF)

Tetrahedron Letters 2017, 58, 2098–2102

pKa values (basicity)

Acetonitrile, H2O

UV-Vis spectrophotometry

Twelve novel phosphazene bases

(X-C6H4-N=N-C6H4-N=PR3) with an unusual combination of properties – high lipophilicity of both neutral and charged forms, lack of localized charges in the cations, and strong spectral changes upon protonation/deprotonation – were synthesized and characterized by UV–Vis spectra, pKa values and lipophilicities (logP values).

Table of structures of the bases, basicities and lipophilicities (PDF)

J. Org. Chem. 2016, 81, 7349–7361

pKa values (basicity)

Tetrahydrofuran, acetonitrile

UV-Vis spectrophotometry

Experimental self-consistent basicity scale of superbases in THF, reaching pKa (estimate of pKa) 35 and spanning more than 30 pKa units, has been compiled, including phosphazenes up to P4, guanidinophosphazenes and phosphorus ylides. The results give access to experimentally supported very high (pKa  over 40) basicities in acetonitrile, which cannot be directly measured. The resuls are linked to the earlier published pKa values of the Schwesinger phosphazenes.

Table of pKa values of superbases in THF and acetonitrile (PDF)

J. Phys. Chem. A 2016, 120, 3663−3669

Gas phase acidities, pKa values

Gas phase, H2O, DMSO

Different methods, both experimental and computational

Careful analysis and comparison of the available pKa values of HCl, HBr, HI, HClO4 and CF3SO3H in water, DMSO and Ga values in the gas-phase has been carried out. As a result, recommended pKa values in water and DMSO are assigned to hydrochloric acid, hydrobromic acid, hydroiodic acid, perchloric acid and trifluoromethanesulfonic acid (triflic acid). In some cases the currently accepted pKa values were revised by more than 10 orders of magnitude

Table of pKa values in water and DMSO for HCl, HBr, HI, HClO4 and CF3SO3H, as well as GA values (PDF)

J. Phys. Chem. A 2016, 120, 2591–2604

GB values, pKa values

Gas phase, MeCN, THF

FT-ICR, UV-Vis spectrophotometry, Quantum chemistry (DFT BP TZVP, DFT B3LYP 6-311+G**)

Experimental gas-phase superbasicity scale spanning 20 orders of magnitude and ranging from bicyclic guanidine MTBD to guanidinophosphazenes and P3 phosphazenes is presented together with solution basicity data in acetonitrile and THF. The most basic compound in the scale – triguanidinophosphazene Et-N=P[N=C(NMe2)2]3 has the highest experimental gas-phase basicity of any organic base ever reported: 273.9 kcal mol-1. The scale includes higher homologues of superbasic phosphazenes, guanidino-substituted phosphazenes and a number of recently introduced bisphosphazene and bis-guanidino proton sponges.

This advancement was made possible by a novel FT-ICR-MS setup with the unique ability to generate and control in the ICR cell sufficient vapor pressures of two delicate compounds having low volatility, which enables determining their basicity difference.

Table of gas-phase basicities and pKa values (PDF)

Angew. Chem. Int. Ed. 2015, 54, 9262–9265.

GB values, pKa values

Gas phase, MeCN, THF

Quantum chemistry (DFT BP TZVP, DFT B3LYP 6-311+G**)

The limits of superbasicity achievable with different families of neutral bases via expanding the molecular framework are explored using DFT computations and a simple model describing the dependence of basicity on the extent of the molecular framework. A number of different core structures of non-ionic organosuperbases are considered (phosphazenes, guanidinophosphazenes, guanidino phosphorus ylides, carbenes etc). Some of the considered bases (guanidino phosphorus carbenes) are expected to reach gas-phase basicity around 370 kcal mol-1, thus being the most basic neutral bases ever reported. The classical substituted alkylphosphazenes were predicted to reach pKa values of 50 in acetonitrile.

Scheme of basicity trends within superbase families, table of basicities achievable by different base families (PDF)

Anal. Chem. 2015, 87, 2623−2630

Absolute acidity values

H2O : MeCN
H2O : Methanol

Differential potentiometry

This work introduces a conceptually new approach of measuring pH of mixed-solvent liquid chromatography (LC) and liquid chromatography mass spectrometry (LC-MS) mobile phases. The new approach is based on the recently introduced unified pH (pHabs) scale, which enables direct comparison of acidities of solutions made in different solvents, based on chemical potential of the proton in the solutions. This work represents the first experimental realization of the pHabs concept using differential potentiometric measurement for comparison of the chemical potentials of the proton in different solutions (connected by a salt bridge), together with earlier published reference points for obtaining the pHabs values (referenced to the gas phase) or pHabsH2O values (referenced to the aqueous solution). pHabs values for a number of common LC and LC-MS mobile phases have been determined.

Tables of unified pH values (acidities) of common LC and LC-MS mobile phases (PDF)

J. Phys. Chem. A 2015, 119, 735−743

Gas-phase acidities

Gas phase

DFT B3LYP 6-311+G**

The structures and intrinsic gas-phase acidities (GA) of some dodecaborane acids, the derivatives of YB12H11H (Y = PF3, NH3, NF3, NMe3), B12H12H2, and B12H12H (HA, H2A, and HA, respectively) have been computationally explored as new possible directions of creating superstrong Brønsted acids. In general, the GA values of the neutral systems varied according to the substituents in the following order: CF3 < F < Cl and in case of anionic acids: CF3 < Cl < F. The acid B12(CF3)12H2, emerges as the strongest among the considered acids and is expected to be in the gas phase at least as strong as CB11(CF3)11H1H.

The scale of gas-phase acidities of dodecaborane superacids accompanied with some other acids (PDF)

Croat. Chem. Acta 2014, 87, 385–395

pKa values

H2O

Different methods, both experimental and computational

Aqueous pKa values of strong organic bases – DBU, TBD, MTBD, different phosphazene bases (e.g. t-BuP4, EtP2, t-BuP1, t-BuP1(pyrr)), etc – were computed with CPCM, SMD and COSMO-RS approaches. Direct computations and computations with reference pKa values were used. The computational data were combined with experimental pKa values in acetonitrile and water (if available), correlation analysis and common chemical knowledge. The recommended aqueous pKa values are proposed for all investigated bases taking into account all available information. Several of the bases are true superbases with pKa values in water around 20 and above.

pKa values strong bases – DBU, TBD, MTBD, different phosphazene bases (e.g. t-BuP4, EtP2, t-BuP1, t-BuP1(pyrr)), etc – in water (PDF)

Angew. Chem. Int. Ed. 2014, 53, 1435-1438

pKa values

THF

UV-Vis Spectrophotometry

Synthesis and basicity of new organosuperbases, N,N’-bis(imidazolyl)guanidine bases (BIG bases), is reported. Their pKa values, determined as 26.1–29.3 in tetrahydrofuran, reach higher than any of the following superbases: DBU, TBD, TMG (tetramethylguanidine), Verkade’s base, Schwesinger’s P1-phosphazenes (t-BuP1, EtP1, MeP1, …), or even the guanidino-phosphazenes. They are probably the strongest known phosphorous-free neutral organic bases both in solution and in the gas phase.

pKa values in THF and some other properties of the BIG superbases (PDF)

pKa values in THF of some common superbases: TMG, tBuP1(pyrr), TBD, Verkade’s base, guanidino-phosphazene HP1(tmg) (PDF)

J. Phys. Org. Chem. 2014, 27, 676–679

gas-phase acidity (GA) values

gas phase

FT-ICR, quantum chemistry (DFT B3LYP 6-311+G**)

The gas-phase acidity (GA) values were determined (using the FT-ICR equilibrium method) for a number of perfluoroalkyl-substituted sulfonylimides, e.g. Tf2NH (bis-trifyl-imide, bis-triflimide), (C2F5SO2)2NH, (C4F9SO2)2NH and others. The GA scale below (CF3SO2)2NH  (bis-trifylimide, GA = 286.5 kcal mol-1) was extended and partially revised. The GA value of (C4F9SO2)2NH, which is currently the strongest acid was revised from 284.1 to 278.6 kcal mol-1.

Gas-phase acidities of of perfluoroalkyl-substituted sulfonylimides (PDF)

Angew. Chem. Int. Ed. 2013, 52, 11569-11572

pKa values

Acetonitrile

UV-Vis Spectrophotometry

MeCN pKa values of Chiral Brønsted Acid Catalysts (organocatalysts) of the following types: BINOL-phosphoric acids, NTPA (N-trifylphosphoramide) and sulfurylimides (JINGLE, BINOL-bis(sulfurylimide)).

pKa values in acetonitrile of chiral Brønsted acid catalysts (BINOL, NTPA and JINGLE derivatives) (PDF)

Chem. Sci, 2013, 4, 2788-2796

pKa values

Acetonitrile, 1,2-Dichloroethane

UV-Vis Spectrophotometry

Basicity (pKa values) of a number of triaryl phosphines (phosphanes) (metal-free hydrogen activation catalysts), most of them derivatives of triphenylphosphine (triphenylphosphine). The rate of hydrogenation is strongly dependent on the electronic nature of the phosphine and of the acidity of the corresponding phosphonium cation. A careful balance of these two factors provides highly efficient metal-free hydrogenation catalysts.

Basicity constants (pKa values) of phosphines catalysts in acetonitrile and 1,2-dichloroethane (PDF)

J. Phys. Org. Chem. 2013, 26, 162-170.

pKa values, gas-phase acidity values

Acetonitrile, Water, 1,2-Dichloroethane, Gas phase

UV-Vis Spectrophotometry, FT-ICR, quantum chemistry (DFT B3LYP 6-311+G**), COSMO-RS, SMD

Acidities (pKa) of a number of different acids including the well-known superacids trifluoromethanesulfonic (triflic) acid, HBr, HI, bis-trifylimide (Tf2NH, bistriflimide), etc as well as weaker acids (HCl, acetic acid, phenol) etc are presented in media of different physical and chemical nature: water, acetonitrile (AN, MeCN), 1,2-dichloroethane (DCE) and the gas phase, with special emphasis on strong acids. Dependence of the acidity trends on moving from water to the gas phase on the nature of the acidity centre and the molecular structure are analyzed. The acidity orders are different in water, AN, DCE and the gas phase. It is demonstrated that the decisive factor for behavior of the acids when transferring between different media is the extent of charge delocalization in the anion and that the recently introduced WAPS parameter in spite of its simplicity enables interpretation of the trends in the majority of cases.

pKa values (scheme) in water, acetonitrile, dichloroethane and gas-phase acidities (PDF)

 

Table of pKa values in water, acetonitrile, 1,2-dichloroethane and gas phase (PDF)

 

A more recent table with some new and some updated pKa values in water, acetonitrile, 1,2-dichloroethane and gas phase (PDF)

Chem. Eur. J. 2012, 18, 3621 – 3630

pKa values, gas-phase basicities

MeCN, gas phase

UV-Vis Spectrophotometry

A New Class of Organosuperbases – N-Alkyl-1,3-dialkyl-4,5-dimethylimidazol-2-ylidene Amines (imidazolidine ylidene amines) – is presented that by the base strength (pKa values, gas-phase basicities) reaches higher than the common organosuperbases DBU, TMG or the Schwesinger P1 phosphazenes.

pKa table of Superbases in acetonitrile (PDF)

Eur. J. Org. Chem. 2012, 2167-2172

pKa values

Acetonitrile

UV-Vis Spectrophotometry

Basicity (pKa values) of a number of phosphanes (phosphines) – both monophosphanes (monophosphines) and diphosphanes (diphosphines, common ligands in catalysts) – and amines in MeCN. Compounds: triphenylphosphine, trimethylphosphine, bis-diphenylphosphinoethane, bis-diphenylphosphinopropane, BINAP, BIPHEP, etc. The possibility of intramolecular hydrogen bond formation in protonated diphosphines is assessed.

Table of pKa values in acetonitrile (PDF)

"Design and acidity measurements of superacidic molecules", presented at ESOR XIII Tartu, on 14.09.2011

pKa values, gas-phase acidity values

MeCN, 1,2-dichloroethane, gas phase

Spectrophotometry, FT-ICR, quantum chemistry (DFT B3LYP 6-311+G**)

An overview was given about the principles of design and acidity measurement of superacids (superacidic molecules), illustrated by numerous acidity data.

Full talk (PDF)

Chem. Eng. J. 2011, 171, 794-800

pKa values

MeCN

COSMO-RS (and some experimental from different sources)

pKa values of different CO2-binding organic liquids (CO2BOLs) have been calculated (using COSMO-RS) or collected from the literature and related to the performance of the CO2BOLs in CO2 capture.

pKa table in acetonitrile (PDF)

J. Org. Chem. 2011, 76, 391-395

pKa values

1,2-dichloroethane (also acetonitrile)

Spectrophotometric

Relative acidities of 64 strong acids (some of them superacids) in 1,2-dichloroethane and 54 strong acids in acetonitrile. Included are numerous sulfonimides, cyanocarbon acids and well-known mineral acids, such as HCl, HBr, HI, H2SO4, HNO3, HBF4, CF3SO3H, FSO3H, HClO4, (CF3SO2)2NH (Tf2NH, bis-triflimide) and (C2F5SO2)2NH. Contains some pKa values of acid catalysts.

Table of pKa values in 1,2-dichloroethane (with estimated values in MeCN) (PDF)

 

Table of pKa values in MeCN (PDF)

J. Phys. Chem. A 2010, 114, 10694-10699

Gas-phase basicity values

Gas phase

FT-ICR, quantum chemistry (W1, G2)

Gas-phase basicity values for weak bases: CS2, water, FCN, C2H4, CF3CN, (CF3)2CHOH, F2NH, CF3CHO, C6F6, CH3Cl, (CF3)3COH, CF3COCl, (CN)2, FSO2Cl, SO2, (CF3)2CO, COS, F2CO, CF3CCH, (CF3)2O and SO2F2. The assigned values have been obtained by combining and critically evaluating data from multiple experimental and theoretical sources and are thus expected to be highly reliable.

Table of gas-phase basicity (GB) values, ladder of GB measurements, correlations between GB values from different sources (PDF)

Angew. Chem. Int. Ed. 2010, 49, 6885-6888.

Absolute acidity values

Acetonitrile, DMSO, water, benzene, etc.

Computations using the rCCC model

On the basis of the absolute chemical potential of the proton, a unified absolute pH scale is introduced that is universally applicable in the gas phase, in solution, and in the solid state. With this scale it is possible to directly compare acidities in different media and to give a thermodynamically meaningful definition of superacidity.

Table of available acidity ranges in selected solvents (PDF)

J. Phys. Chem. A 2009, 113, 8421-8424

pKa values and Gas-phase acidity values

Acetonitrile, gas phase

Spectrophotometric, FT-ICR, G3(MP2), DFT B3LYP 6-311+G**

Gas-phase acidity and pKa values in MeCN for a number of aromatic sulfonimides, fluorinated aliphatic sulfonimides, including Tf2NH and (C2F5SO2)2NH, and some other acids. The work presents revision of the gas-phase acidity (GA) scale from (CF3CO)2NH to (C2F5SO2)2NH, i.e. about a 24 kcal mol-1 range of gas phase acidities and ends the controversy between experiment and computations in this acidity range.

Table of experimental and computational gas-phase acidities and pKa values in acetonitrile (PDF)

J. Comp. Chem. 2009, 30, 799-810

pKa values

Acetonitrile

Spectrophotometric

Experimental pKa values of more than 200 neutral acids in acetonitrile (from our group and from other authors) ranging from pKa 3.6 to 29.

Acids: alcohols, carboxylic acids (acetic acid, trifluoroacetic acid, benzoic acid, different diacids, e.g. phthalic acid, oxalic acid, succinic acid), phenols (nitrophenols, chlorophenols, 2,4-dinitrophenol, 2,4,6-Trinitrophenol (picric acid), etc), sulfonic acids (para-toluene sulfonic acid, substituted benzenesulfonic acids), anilines, sulfonamides, phenylmalononitriles, diphenylacetonitriles, strong acids (perchloric acid, fluorosulfuric acid, methanesulfonic acid, 4-toluenesulfonic acid) acid catalysts, etc.

The work aims at computational (COSMO-RS) estimation of MeCN pKa values and the experimental values of our group are used as fit data set and values from other authors as test data set.

Tables of pKa values (PDF)

J. Org. Chem. 2008, 73, 2607-2620

pKa values and Gas-phase acidity values

Acetonitrile, DMSO, Water, gas phase

Spectrophotometric, FT-ICR, DFT B3LYP 6-311+G**

Gas-phase acidity and pKa values for a number of poly-CF3-substituted aromatic compounds. Included are (CF3)5Phenol, (CF3)5Aniline, (CF3)5Toluene and (CF3)5Phenylmalononitrile.

Table of experimental pKa values and Gas-phase acidities (PDF)

Chem. Eur. J. 2007, 13, 7631-7643

pKa values and Gas-phase basicity values

Acetonitrile, Tetrahydrofuran, gas phase

Spectrophotometric, FT-ICR, DFT B3LYP 6-311+G**

Gas-phase basicity and pKa values for a number of diamines and related monoamines.

Included are different substituted diamines: 1,3-propanediamine (1,3-diaminopropane) and its derivatives, tetramethylated 1,2-ethanediamine (1,2-diaminoethane) and 1,4-butanediamine (1,4-diaminobutane), piperidine, piperazine, bispidine, dimethylbispidine.

Schemes of base structures, table of pKa and gas-phase basicity values (PDF)

"Brønsted Acidity of Neutral and Cationic Acids in Nonaqueous Solvents: Recent Developments", (INOR 1036) presented at the ACS Spring meeting Mar 27, 2007, Chicago

pKa values

Acetonitrile, Heptane, 1,2-Dichloroethane, THF, gas phase

spectrophotometric, FT-ICR

This is a poster summarizing the Brønsted acidity and basicity data gathered by our group during the recent years.

Full poster (PDF)

J. Phys. Chem. A 2007, 111, 1245-1250

Gas-phase basicity values

gas phase

FT-ICR, spectrophotometric

Gas-phase basicity for 30 superbases: phosphazene superbases: P2-phosphazenes (EtP2, PhP2, …), P1-phosphazenes (t-BuP1, EtP1, MeP1, …), BEMP superbase; MTBD, ETBD, ITBD, Verkade's superbases

Scheme of base structures, table gas-phase basicity values (PDF)

Anal. Chim. Acta. 2006, 566, 290-303

Uncertainty

MeCN

 

Spectrophotometric

 

Uncertainty estimation in measurement of pKa values in nonaqueous media (solvents) using two different approaches.

Table of pKa values, experimental measurement results and uncertainty values (PDF)

J. Org. Chem. 2006, 71, 2829-2838

pKa values
of acids

 

Acetonitrile

 

Spectrophotometric

 

pKa values of 93 neutral acids in acetonitrile ranging from pKa 3.7 to 28.1.

Acids: alcohols, carboxylic acids (acetic acid, benzoic acid), phenols (2,4-dinitrophenol, picric acid, etc), sulfonic acids (para-toluene sulfonic acid, substituted benzenesulfonic acids), anilines, sulfonamides, phenylmalononitriles, diphenylacetonitriles, etc.

Titrants: trifluoromethanesulfonic acid (triflic acid) and phosphazenes t-BuP1(pyrr) and EtP2(dma)

Table of pKa values and experimental measurement results (PDF)

J. Org. Chem. 2006, 71, 7155-7164

pKa values

 

Acetonitrile

 

Spectrophotometric

 

Acetonitrile pKa values of 10 substituted bispidine bases.

Table of bispidine structures and table of pKa measurement results (PDF)

J. Am. Chem. Soc. 2005, 127, 17656-17666

pKa values

 

GPB, PA

Tetrahydrofuran

 

Calculation

Spectrophotometric

 

DFT B3LYP

6-311+G**

pKa values of a number of organosuperbases – phosphazene bases, guanidinophosphazenes and related bases – have been determined.

Table of pKa values of te superbases and experimental measurement results and table of results of basicity calculations (PDF)

J. Org. Chem. 2005, 70, 1019-1028

pKa values
of bases

Acetonitrile

Spectrophotometric

pKa values of 89 neutral bases in acetonitrile ranging from 4-Cl-2-NO2-Aniline (pKa = 3.80) to 4-MeO-C6H4-N=P(N=P(Nme2)3)(Nme2) (pKa = 31.99).

Among the bases are: phosphazene superbases, DBU, TBD, MTBD superbase, proton sponge, triethylamine, pyrrolidine (and other substituted amines) pyridine and substituted pyridines (DMAP, etc), aniline and substituted anilines.

Please use the slightly revised values from Eur. J. Org. Chem. 2019.

Table of pKa values and experimental measurement results (PDF) (Please use the slightly revised values from this paper: Eur. J. Org. Chem. 2019)

J. Org. Chem. 2003, 68, 9988-9993

pKip, pKa values

 

GPB

Tetrahydrofuran

Spectrophotometric

 

FT-ICR spectrometric

pKa and pKip values of 31 bases in tetrahydrofuran ranging from 4‑CF3-C6H4-P1(pyrr) (pKa = 14,6) to 2‑Cl‑C6H4‑P4(pyrr) (pKa = 26,6). Gas-Phase basicities of 10 bases.

Tables of pKip, pKa and GBP values and experimental measurements results (PDF)

J. Org. Chem. 2003, 68, 7795-7799

pKip values

Heptane

Spectrophotometric

Relative pKip values of 21 weak acids in heptane.

Table of pKip values and experimental measurements results (PDF)

J. Chem. Soc., Perkin Trans. 2. 2002, 1950-1955

pKa values

Acetonitrile

Spectrophotometric

Acetonitrile pKa values of some amides and imidines of benzoic acid. The acidifying effect of the substituent =NSO2CF3.

pKa table and experimental measurements results (PDF)

Inorg. Chim. Acta. 2002, 340, 87-96.

pKa table

Acetonitrile

Spectrophotometric

pKa values for neutral and cationic bases in MeCN. Used a different calculation method to get also pKa values of cationic bases.

pKa table and experimental measurements results (PDF)

J. Org. Chem. 2002, 67, 1873-1881

pKip, pKa values

Tetrahydrofuran

Spectrophotometric

pKa and pKip values of 45 bases in tetrahydrofuran ranging from 2-MeO-Pyridine (pKa = 2,6) to EtP1(pyrr) (pKa = 21,5).

Among the bases are: various phosphazene superbases (incl. several Schwesinger's phosphazenes), DBU, TBD, TMG, pyridine, aniline, etc.

Table of pKip and pKa values, experimental measurements results and Table with AN pKa and literature values (PDF)

J. Chem. Soc., Perkin Trans. 2. 2001, 229-232

pKa values

 

GPA

Dimethyl

sulfoxide

Potentiometric

 

FT-ICR spectrometric

The acidifying effect of the substituent =NSO2CF3 on the acidity of derivatives of benzenesulfonamide and toluene-p-sulfonamide in the gas phase and in dimethyl sulfoxide (DMSO)

The GPB and DMSO pKa values of toluene-p-sulfonamide (PDF)

J. Org. Chem. 2000, 65, 6202-6208

pKa table

MeCN

Spectrophotometric

pKa values of 29 bases in acetonitrile ranging from Pyridine (pKa = 12,33) to DBU (pKa = 24,13)

Table of pKa values and experimental measurement results (PDF)

J. Chem. Soc., Perkin Trans. 2. 2000, 1125-1133

pKa values

 

GPA-s

Dimethyl

sulfoxide

Potentiometric

 

FT-ICR spectrometric

Comparison of Brønsted acidities of neutral CH-acids in gas phase and dimethyl sulfoxide. A voluminous acidity table in DMSO and gas phase (Fluorene, indene, cyclopentadiene, fluoradene, …).

Acidity table (table of pKa values) in dimethyl sulfoxide and GPB (PDF)

J. Org. Chem. 1998, 63, 7868-7874

pKa table

Acetonitrile

Spectrophotometric

pKa values (dissociation constants) of 36 acids in acetonitrile ranging from 4-Cl-C6H4-SO(=NTf)-NH-SO2-C6H4-4-NO2 (pK = 3.75) to 2,4-dinitrophenol (pK = 16.66)

Table of dissociation constants (pKa values) in acetonitrile and experimental measurement results (PDF)

J. Org. Chem. 1997, 62, 8479-8483

pKip values

Heptane

Spectrophotometric

Relative pKip (acidity constants) values of 6 weak acids in heptane.

Table of pKip values and experimental measurements results (PDF)

 

Comments

Should you have any questions regarding the data, the used experimental, data treatment or computational methods, etc, please do not hesitate to contact Ivo Leito (e-mail: ivo.leito[at]ut.ee)! Proposals for collaboration in pKa measurement are also most welcome!

All material has been posted on this website in accordance with the copyright rules of the publishers of the articles. That is, no full texts can be posted. To institutional electronic subscribers the full texts of the articles are available from the links in the column "Publication".  Those who do not have online access to the full texts are welcome to e-mail Ivo Leito (ivo.leito[at]@ut.ee) to obtain reprints.

See also the main website of the University of Tartu, Chair of Analytical chemistry

  

University of Tartu 2013-2024

 

Last edited: 09.09.2024