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

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The highlighted papers contain large amounts of pK_a 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	pK_aH and GB values	Acetonitrile, gas phase	UV-Vis spectrometry, Computations	Basicity (pK_aH 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.	pK_aH values of phosphanes in MeCN and GB values (PDF)
Eur. J. Org. Chem. 2023, 26, e202300453	pK_aH and GB values	Acetonitrile, THF, gas phase	UV-Vis spectrometry, Computations	Basicity values in MeCN and THF (pK_aH values) of a number of phosphane (posphine) bases containing the benziphenoneimine (bpi) moiety.	pK_aH values of phosphanes in MeCN and THF (PDF)
Bioorgan. Med. Chem. 2023, 81, 117203	pK_a values	MeCN and MeCN : water mixtures	UV-Vis spectrometry	pK_a and pK_aH 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.	pK_a and pK_aH values, of different drugs, bioactive and related compounds in acetonitrile-water mixtures and acetonitrile (PDF)
Chem. Eur. J. 2022, 29, e202202953	pK_a values	Acetonitrile	UV-Vis spectrometry, ³¹P NMR	pK_a 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 pK_a value.	pK_a values of Singly-linked and Macrocyclic Bisphosphoric Acid catalysts in MeCN (PDF)
Anal. Chem. 2022, 94, 4059-4064	Biphasic pK_a values (pK_a^ow values)	Octanol:Water	UV-Vis spectrometry, ¹H NMR, ¹³C NMR, ³¹P NMR	Biphasic pK_a values (pK_a^ow 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 pK_a value (pK_a^ow 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) pK_a^ow 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 pK_a values (pK_a^ow values ) of 35 acids and extrapolation plot (PDF)
Acc. Chem. Res. 2021, 54, 3108-3123	pK_a values (pK_aH 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 pK_a (pK_aH) 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.	pK_a (pK_aH) values in MeCN and THF, as well as gas-phase basicities of around 30 important superbases (PDF)
Eur. J. Org. Chem. 2021, 1407-1419	pK_a values	Acetonitrile	UV-Vis spectrometry	pK_a 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 pK_a values of 231 acids in acetonitrile (PDF)
J. Am. Chem. Soc. 2020, 142, 15252-15258	pK_a 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 pK_a values of the acids compared benzoic acids with similar substitution.	Acidities (pK_a in MeCN) of the enantioselective carboxylic acid catalysts (PDF)
Angew. Chem. Int. Edit. 2020, 59, 2028-2032	pK_a 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 (pK_a 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	pK_a values (pK_aH values)	Acetonitrile, DMSO, THF, Water	UV-Vis spectrophotometry	pK_a values (pK_aH 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 pK_aH in DMSO, THF or water on the basis of MeCN pK_aH 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 pK_a 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 pK_a values available. Earlier values (published in 2005) changed slightly (usually by 0.00 .. 0.04 pK_a units).	Basicity pK_a (pK_aH) values of 279 bases in acetonitrile (PDF) Basicity pK_a (pK_aH) values of selected bases in water, DMSO, MeCN, THF (PDF)
Int. J. Mass Spec. 2019, 435, 61–68	pK_a and GB values	Acetonitrile, gas phase	FT-ICR, UV-Vis spectrophotometry	Gas-phase basicities and MeCN pK_a 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	pK_a values	Water	¹⁹F NMR	Aqueous pK_a 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 pK_a range from 3.5 to 10 have been measured with ¹⁹F NMR. ¹⁹F NMR pK_a 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 pK_a values
Nature Chemistry 2018, 10, 888-894	pK_a 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	pK_a 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 pK_a data. Examples: How to estimate a pK_a 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 pK_a data of acids and bases in acetonitrile, DMSO, 1,2-DCE, H2O, Tetrahydrofuran, heptane and dimethoxyethane (PDF)
Green Chemistry 2018, 20, 2392-2394	pK_a values	Mixtures of water and methanol	Computations, correlations	pK_a 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	pK_a values, pH_abs 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 pK_a units in 1,2-dichloroethane (DCE) and linked to the unified acidity scale (pH_abs) 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 pK_a values of the acids in 1,2-dichloroethane as well as the pH_abs values of the respective buffer systems, directly comparable to the pH scale in water (PDF)
Angew. Chem. Int. Ed. 2017, 56, 1411–1415	pK_a 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 pK_a of TPP in MeCN is -2.8.
Eur. J. Org. Chem. 2017, 4475–4489	pK_a 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 pK_a values in acetonitrile, as well as a number of pK_a 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 pK_a values in MeCN and H₂O, as well as gas-phase basicity values (PDF)
Tetrahedron Letters 2017, 58, 2098–2102	pK_a 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	pK_a values (basicity)	Tetrahydrofuran, acetonitrile	UV-Vis spectrophotometry	Experimental self-consistent basicity scale of superbases in THF, reaching pK_a (estimate of pK_a) 35 and spanning more than 30 pK_a units, has been compiled, including phosphazenes up to P₄, guanidinophosphazenes and phosphorus ylides. The results give access to experimentally supported very high (pK_a over 40) basicities in acetonitrile, which cannot be directly measured. The resuls are linked to the earlier published pK_a values of the Schwesinger phosphazenes.	Table of pK_a values of superbases in THF and acetonitrile (PDF)
J. Phys. Chem. A 2016, 120, 3663−3669	Gas phase acidities, pK_a values	Gas phase, H₂O, DMSO	Different methods, both experimental and computational	Careful analysis and comparison of the available pK_a 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 pK_a 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 pK_a values were revised by more than 10 orders of magnitude	Table of pK_a 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, pK_a 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 pK_a values (PDF)
Angew. Chem. Int. Ed. 2015,* 54, 9262–9265.*	GB values, pK_a 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 pK_a 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 (pH_abs) 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 pH_abs 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 pH_abs values (referenced to the gas phase) or pH_abs^H2O values (referenced to the aqueous solution). pH_abs 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	pK_a values	H₂O	Different methods, both experimental and computational	Aqueous pK_a 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 pK_a values were used. The computational data were combined with experimental pK_a values in acetonitrile and water (if available), correlation analysis and common chemical knowledge. The recommended aqueous pK_a values are proposed for all investigated bases taking into account all available information. Several of the bases are true superbases with pK_a values in water around 20 and above.	pK_a 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	pK_a values	THF	UV-Vis Spectrophotometry	Synthesis and basicity of new organosuperbases, N,N’-bis(imidazolyl)guanidine bases (BIG bases), is reported. Their pK_a 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.	pK_a values in THF and some other properties of the BIG superbases (PDF) pK_a 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	pK_a values	Acetonitrile	UV-Vis Spectrophotometry	MeCN pK_a values of Chiral Brønsted Acid Catalysts (organocatalysts) of the following types: BINOL-phosphoric acids, NTPA (N-trifylphosphoramide) and sulfurylimides (JINGLE, BINOL-bis(sulfurylimide)).	pK_a values in acetonitrile of chiral Brønsted acid catalysts (BINOL, NTPA and JINGLE derivatives) (PDF)
Chem. Sci, 2013, 4, 2788-2796	pK_a values	Acetonitrile, 1,2-Dichloroethane	UV-Vis Spectrophotometry	Basicity (pK_a 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 (pK_a values) of phosphines catalysts in acetonitrile and 1,2-dichloroethane (PDF)
J. Phys. Org. Chem. 2013, 26, 162-170.	pK_a 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 (pK_a) 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.	pK_a values (scheme) in water, acetonitrile, dichloroethane and gas-phase acidities (PDF) Table of pK_a values in water, acetonitrile, 1,2-dichloroethane and gas phase (PDF) A more recent table with some new and some updated pK_a values in water, acetonitrile, 1,2-dichloroethane and gas phase (PDF)
Chem. Eur. J. 2012, 18, 3621 – 3630	pK_a 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 (pK_a values, gas-phase basicities) reaches higher than the common organosuperbases DBU, TMG or the Schwesinger P1 phosphazenes.	pK_a table of Superbases in acetonitrile (PDF)
Eur. J. Org. Chem. 2012, 2167-2172	pK_a values	Acetonitrile	UV-Vis Spectrophotometry	Basicity (pK_a 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 pK_a values in acetonitrile (PDF)
"Design and acidity measurements of superacidic molecules", presented at ESOR XIII Tartu, on 14.09.2011	pK_a 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	pK_a values	MeCN	COSMO-RS (and some experimental from different sources)	pK_a 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.	pK_a table in acetonitrile (PDF)
J. Org. Chem. 2011, 76, 391-395	pK_a 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 pK_a values of acid catalysts.	Table of pK_a values in 1,2-dichloroethane (with estimated values in MeCN) (PDF) Table of pK_a 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	pK_a values and Gas-phase acidity values	Acetonitrile, gas phase	Spectrophotometric, FT-ICR, G3(MP2), DFT B3LYP 6-311+G**	Gas-phase acidity and pK_a 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 pK_a values in acetonitrile (PDF)
J. Comp. Chem. 2009, 30, 799-810	pK_a values	Acetonitrile	Spectrophotometric	Experimental pK_a values of more than 200 neutral acids in acetonitrile (from our group and from other authors) ranging from pK_a 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 pK_a 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 pK_a values (PDF)
J. Org. Chem. 2008, 73, 2607-2620	pK_a values and Gas-phase acidity values	Acetonitrile, DMSO, Water, gas phase	Spectrophotometric, FT-ICR, DFT B3LYP 6-311+G**	Gas-phase acidity and pK_a values for a number of poly-CF₃-substituted aromatic compounds. Included are (CF₃)₅Phenol, (CF₃)₅Aniline, (CF₃)₅Toluene and (CF₃)₅Phenylmalononitrile.	Table of experimental pK_a values and Gas-phase acidities (PDF)
Chem. Eur. J. 2007, 13, 7631-7643	pK_a values and Gas-phase basicity values	Acetonitrile, Tetrahydrofuran, gas phase	Spectrophotometric, FT-ICR, DFT B3LYP 6-311+G**	Gas-phase basicity and pK_a 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 pK_a 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	pK_a 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 pK_a values in nonaqueous media (solvents) using two different approaches.	Table of pK_a values, experimental measurement results and uncertainty values (PDF)
J. Org. Chem. 2006, 71, 2829-2838	pK_a values of acids	Acetonitrile	Spectrophotometric	pK_a values of 93 neutral acids in acetonitrile ranging from pK_a 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 pK_a values and experimental measurement results (PDF)
J. Org. Chem. 2006, 71, 7155-7164	pK_a values	Acetonitrile	Spectrophotometric	Acetonitrile pK_a values of 10 substituted bispidine bases.	Table of bispidine structures and table of pK_a measurement results (PDF)
J. Am. Chem. Soc. 2005, 127, 17656-17666	pK_a values GPB, PA	Tetrahydrofuran Calculation	Spectrophotometric DFT B3LYP 6-311+G**	pK_a values of a number of organosuperbases – phosphazene bases, guanidinophosphazenes and related bases – have been determined.	Table of pK_a values of te superbases and experimental measurement results and table of results of basicity calculations (PDF)
J. Org. Chem. 2005, 70, 1019-1028	pK_a values of bases	Acetonitrile	Spectrophotometric	pK_a values of 89 neutral bases in acetonitrile ranging from 4-Cl-2-NO₂-Aniline (pK_a = 3.80) to 4-MeO-C₆H₄-N=P(N=P(Nme₂)₃)(Nme₂) (pK_a = 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 pK_a 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	pK_ip, pK_a values GPB	Tetrahydrofuran	Spectrophotometric FT-ICR spectrometric	pK_a and pK_ip values of 31 bases in tetrahydrofuran ranging from 4‑CF₃-C₆H₄-P₁(pyrr) (pK_a = 14,6) to 2‑Cl‑C₆H₄‑P₄(pyrr) (pK_a = 26,6). Gas-Phase basicities of 10 bases.	Tables of pK_ip, pK_a and GBP values and experimental measurements results (PDF)
J. Org. Chem. 2003, 68, 7795-7799	pK_ip values	Heptane	Spectrophotometric	Relative pK_ip values of 21 weak acids in heptane.	Table of pK_ip values and experimental measurements results (PDF)
J. Chem. Soc., Perkin Trans. 2. 2002, 1950-1955	pK_a values	Acetonitrile	Spectrophotometric	Acetonitrile pK_a values of some amides and imidines of benzoic acid. The acidifying effect of the substituent =NSO₂CF₃.	pK_a table and experimental measurements results (PDF)
Inorg. Chim. Acta. 2002, 340, 87-96.	pK_a table	Acetonitrile	Spectrophotometric	pK_a values for neutral and cationic bases in MeCN. Used a different calculation method to get also pK_a values of cationic bases.	pK_a table and experimental measurements results (PDF)
J. Org. Chem. 2002, 67, 1873-1881	pK_ip, pK_a values	Tetrahydrofuran	Spectrophotometric	pK_a and pK_ip values of 45 bases in tetrahydrofuran ranging from 2-MeO-Pyridine (pK_a = 2,6) to EtP₁(pyrr) (pK_a = 21,5). Among the bases are: various phosphazene superbases (incl. several Schwesinger's phosphazenes), DBU, TBD, TMG, pyridine, aniline, etc.	Table of pK_ip and pK_a values, experimental measurements results and Table with AN pK_a and literature values (PDF)
J. Chem. Soc., Perkin Trans. 2. 2001, 229-232	pK_a 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 pK_a values of toluene-p-sulfonamide (PDF)
J. Org. Chem. 2000, 65, 6202-6208	pK_a table	MeCN	Spectrophotometric	pK_a values of 29 bases in acetonitrile ranging from Pyridine (pK_a = 12,33) to DBU (pK_a = 24,13)	Table of pK_a values and experimental measurement results (PDF)
J. Chem. Soc., Perkin Trans. 2. 2000, 1125-1133	pK_a 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 pK_a values) in dimethyl sulfoxide and GPB (PDF)
J. Org. Chem. 1998, 63, 7868-7874	pK_a table	Acetonitrile	Spectrophotometric	pK_a 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 (pK_a values) in acetonitrile and experimental measurement results (PDF)
J. Org. Chem. 1997, 62, 8479-8483	pK_ip values	Heptane	Spectrophotometric	Relative pK_ip (acidity constants) values of 6 weak acids in heptane.	Table of pK_ip values and experimental measurements results (PDF)

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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 pK_a measurement are also most welcome!

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University of Tartu 2013-2024

Last edited: 09.09.2024

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

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