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Ivo Leito - One of the best experts on this subject based on the ideXlab platform.
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on the Basicity of conjugated nitrogen heterocycles in different media
European Journal of Organic Chemistry, 2017Co-Authors: Mart Lokov, Sofja Tshepelevitsh, Agnes Heering, Paul G Plieger, Robert Vianello, Ivo LeitoAbstract:In this work we explored the relationship between the structure and solvent effects on the Basicity of a large selection of conjugated N-heterocyclic nitrogen bases in different media: the polar aprotic solvent acetonitrile, the polar protic solvent water and the gas phase. Altogether, 58 previously unpublished Basicity values in different media for 39 compounds are presented, including 30 experimentally determined pKa values in acetonitrile. We present the pKa and gas-phase Basicity values for quino[7,8-h]quinoline, which is one of the most basic conjugated nitrogen heterocyclic compounds without Basicity-enhancing substituents. The trends in Basicity are rationalized by comparing the Basicity data of related compounds in different solvents, as well as by using isodesmic reactions. The gas-phase Basicity is predominantly determined by the ability of a molecule to disperse the excess positive charge over a large number of atoms. In solution the situation is less clear and smaller systems with localized charge often lead to higher basicities because of solvent effects. In particular, it was found that the fusion of an additional benzene ring does not always lead to an increase in Basicity in solution: its effect can be either Basicity-increasing or -decreasing, depending on the ring size, number and position of nitrogen atoms and medium. A correlation between the measured pKa values in MeCN and in water suggests that these two different solvents exert a similar effect on the Basicity of the studied heterocycles.
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Experimental Basicities of Superbasic Phosphonium Ylides and Phosphazenes
The Journal of Organic Chemistry, 2016Co-Authors: Jaan Saame, Agnes Kutt, Ivari Kaljurand, Toomas Rodima, Ilmar A Koppel, Sofja Tshepelevitsh, Tõiv Haljasorg, Ivo LeitoAbstract:Experimental basicities of some of the strongest superbases ever measured (phosphonium ylides) are reported, and by employing these compounds, the experimental self-consistent Basicity scale of superbases in THF, reaching a pKα (estimate of pKa) of 35 and spanning more than 30 pKa units, has been compiled. Basicities of 47 compounds (around half of which are newly synthesized) are included. The solution Basicity of the well-known t-Bu-N═P4(dma)9 phosphazene superbase is now rigorously linked to the scale. The compiled scale is a useful tool for further Basicity studies in THF as well as in other solvents, in particular, in acetonitrile. A good correlation between basicities in THF and acetonitrile spanning 25 orders of magnitude gives access to experimentally supported very high (pKa > 40) basicities in acetonitrile, which cannot be directly measured. Analysis of structure–Basicity trends is presented.
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Experimental Basicities of Phosphazene, Guanidinophosphazene, and Proton Sponge Superbases in the Gas Phase and Solution
2016Co-Authors: Ivari Kaljurand, Jaan Saame, Toomas Rodima, Ivar Koppel, Ilmar A. Koppel, Julius F. Kögel, Jörg Sundermeyer, Uwe Köhn, Martyn P. Coles, Ivo LeitoAbstract:Experimental gas-phase superBasicity scale spanning 20 orders of magnitude and ranging from bicyclic guanidine 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene to triguanidinophosphazenes and P3 phosphazenes is presented together with solution Basicity data in acetonitrile and tetrahydrofuran. The most basic compound in the scaletriguanidinophosphazene Et–NP[NC(NMe2)2]3has the highest experimental gas-phase Basicity of an organic base ever reported: 273.9 kcal mol–1. The scale includes besides the higher homologues of classical superbasic phosphazenes and several guanidino-substituted phosphazenes also a number of recently introduced bisphosphazene and bis-guanidino proton sponges. This advancement was made possible by a newly designed Fourier transform ion cyclotron resonance (ICR) mass spectrometry 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. The obtained experimental gas-phase and solution Basicity data are analyzed in terms of structural and solvent effects and compared with data from theoretical calculations
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Basicity of phosphanes and diphosphanes in acetonitrile
European Journal of Organic Chemistry, 2012Co-Authors: Kristjan Haav, Agnes Kutt, Jaan Saame, Ivo LeitoAbstract:Phosphanes are widely used in organic chemistry. Their Basicity is important in determining their behavior in solutions of different acidity. We report a study of the basicities of various mono- and diphosphanes in acetonitrile, some of them of significant practical interest (BINAP, BIPHEP). The basicities of the studied phosphanes in acetonitrile are in the pKa range of 4–16. From the results, the relationship between the structure and Basicity of the phosphanes has been analyzed and compared with that of amines of similar structure. A remarkably stronger change in Basicity can be observed in the amines in comparison with the phosphanes when alkyl groups are replaced by aryl groups. This is mainly caused by resonance between the aryl group and the lone pair of the Basicity center, which is strong in the case of the nitrogen atom and weak in the case of the phosphorus atom. The results of the Basicity measurements of the diphosphanes in this work has led to two tentative conclusions: (1) there is no intramolecular hydrogen bond in protonated diphosphanes with an alkyl backbone, and (2) there may be a weak intramolecular hydrogen bond in protonated diphosphanes with an aromatic backbone.
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experimental gas phase Basicity scale of superbasic phosphazenes
Journal of Physical Chemistry A, 2007Co-Authors: Ivari Kaljurand, Agnes Kutt, Toomas Rodima, Ilmar A Koppel, Masaaki Mishima, Evaingrid Room, Ivar Koppel, Ivo LeitoAbstract:Seventeen superbasic phosphazenes and two Verkade's bases were used to supplement and extend the experimental gas-phase Basicity scale in the superbasic region. For 19 strong bases the gas-phase Basicity values (GB) were determined for the first time. Among them are such well-known bases as BEMP (1071.2 kJ/mol), Verkade's Me-substituted base (1083.8 kJ/mol), Et−NP(NMe2)2-NP(NMe2)3 (Et−P2 phosphazene, 1106.9 kJ/mol), and t-Bu−NP(NMe2)3 (t-Bu−P1 phosphazene, 1058.0 kJ/mol). For the first time experimental GB values were determined for P2 phosphazenes. Together with our previous results self-consistent experimental gas-phase Basicity scale between 1020 and 1107 kJ/mol is now established. This way an important region of the gas-phase Basicity scale, which was earlier dominated by metal hydroxide bases, is now covered also with organic bases making it more accessible for further studies. The GB values for several superbases were calculated using density functional theory at the B3LYP/6-311+G** level. For the p...
Pierrecharles Maria - One of the best experts on this subject based on the ideXlab platform.
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Push–Pull Effect on the Gas-Phase Basicity of Nitriles: Transmission of the Resonance Effects by Methylenecyclopropene and Cyclopropenimine π-Systems Substituted by Two Identical Strong Electron Donors
'MDPI AG', 2021Co-Authors: Ewa D Raczynska, Jeanfrancois Gal, Pierrecharles Maria, Hamid SaeidianAbstract:The gas-phase Basicity of nitriles can be enhanced by a push–pull effect. The role of the intercalated scaffold between the pushing group (electron-donor) and the pulling (electron-acceptor) nitrile group is crucial in the Basicity enhancement, simultaneously having a transmission function and an intrinsic contribution to the Basicity. In this study, we examine the methylenecyclopropene and the N-analog, cyclopropenimine, as the smallest cyclic π systems that can be considered for resonance propagation in a push–pull system, as well as their derivatives possessing two strong pushing groups (X) attached symmetrically to the cyclopropene scaffold. For Basicity and push–pull effect investigations, we apply theoretical methods (DFT and G2). The effects of geometrical and rotational isomerism on the Basicity are explored. We establish that the protonation of the cyano group is always favored. The push–pull effect of strong electron donor X substituents is very similar and the two π-systems appear to be good relays for this effect. The effects of groups in the two cyclopropene series are found to be proportional to the effects in the directly substituted nitrile series X–C≡N. In parallel to the Basicity, changes in electron delocalization caused by protonation are also assessed on the basis of aromaticity indices. The calculated proton affinities of the nitrile series reported in this study enrich the gas-phase Basicity scale of nitriles to around 1000 kJ mol−1
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enhanced Basicity of push pull nitrogen bases in the gas phase
Chemical Reviews, 2016Co-Authors: Ewa D Raczynska, Jeanfrancois Gal, Pierrecharles MariaAbstract:Nitrogen bases containing one or more pushing amino-group(s) directly linked to a pulling cyano, imino, or phosphoimino group, as well as those in which the pushing and pulling moieties are separated by a conjugated spacer (C═X)n, where X is CH or N, display an exceptionally strong Basicity. The n-π conjugation between the pushing and pulling groups in such systems lowers the Basicity of the pushing amino-group(s) and increases the Basicity of the pulling cyano, imino, or phosphoimino group. In the gas phase, most of the so-called push–pull nitrogen bases exhibit a very high Basicity. This paper presents an analysis of the exceptional gas-phase Basicity, mostly in terms of experimental data, in relation with structure and conjugation of various subfamilies of push–pull nitrogen bases: nitriles, azoles, azines, amidines, guanidines, vinamidines, biguanides, and phosphazenes. The strong Basicity of biomolecules containing a push–pull nitrogen substructure, such as bioamines, amino acids, and peptides contai...
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Enhanced Basicity of Push–Pull Nitrogen Bases in the Gas Phase
2016Co-Authors: Ewa D. Raczyńska, Jean-françois Gal, Pierrecharles MariaAbstract:Nitrogen bases containing one or more pushing amino-group(s) directly linked to a pulling cyano, imino, or phosphoimino group, as well as those in which the pushing and pulling moieties are separated by a conjugated spacer (CX)n, where X is CH or N, display an exceptionally strong Basicity. The n-π conjugation between the pushing and pulling groups in such systems lowers the Basicity of the pushing amino-group(s) and increases the Basicity of the pulling cyano, imino, or phosphoimino group. In the gas phase, most of the so-called push–pull nitrogen bases exhibit a very high Basicity. This paper presents an analysis of the exceptional gas-phase Basicity, mostly in terms of experimental data, in relation with structure and conjugation of various subfamilies of push–pull nitrogen bases: nitriles, azoles, azines, amidines, guanidines, vinamidines, biguanides, and phosphazenes. The strong Basicity of biomolecules containing a push–pull nitrogen substructure, such as bioamines, amino acids, and peptides containing push–pull side chains, nucleobases, and their nucleosides and nucleotides, is also analyzed. Progress and perspectives of experimental determinations of GBs and PAs of highly basic compounds, termed as “superbases”, are presented and benchmarked on the basis of theoretical calculations on existing or hypothetical molecules
Seshadri Seetharaman - One of the best experts on this subject based on the ideXlab platform.
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effect of al2o3 addition on the precipitated phase transformation in ti bearing blast furnace slags
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2016Co-Authors: Yongqi Sun, Seshadri Seetharaman, Lili Liu, Xidong Wang, Zuotai ZhangAbstract:The present paper aims to provide a fundamental understanding on phase change of Ti-enriched crystalline phase induced by Al2O3 addition in Ti-bearing blast furnace slags with different basicities using Single Hot Thermocouple Technique and X-ray Diffraction. The results showed that an increase in the Al2O3 content led to phase change from rutile or perovskite to Mg3Al4Ti8O25 and prompted crystallization of the slags with Basicity of 0.60 and 0.75, whereas only CaTiO3 was precipitated at a Basicity of 0.95. Both thermodynamic and kinetic analyses were conducted to study the slag crystallization, which would throw light on phase change and enhanced crystallization. To further reveal the relationship with Al2O3 addition on slag structure and crystallization, Fourier transform infrared spectroscopy and magic angle spinning-nuclear magnetic resonance were adopted, with AlO4 tetrahedra and AlO6 octahedra observed in the slag. For slags with the Basicity of 0.60 and 0.75, AlO6 octahedron, which was suggested to induce the phase change from TiO2 or CaTiO3 to Mg3Al4Ti8O25, was detected at high Al2O3 content. On the other hand, in slags with the Basicity of 0.95, abundant Ca2+ may be connected to TiO6 octahedra, resulting in CaTiO3 formation.
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estimation of viscosity for blast furnace type slags
Ironmaking & Steelmaking, 2007Co-Authors: Amitabh Shankar, Marten Gornerup, A K Lahiri, Seshadri SeetharamanAbstract:A viscosity model based on a new definition of Basicity has been proposed for blast furnace type slags. Conceptually, this definition of Basicity is close to Bell's definition of Basicity as used for modelling of sulphide capacity of blast furnace type slags. The model developed in the present work is applicable for wide range of alumina, magnesia and titania containing blast furnace slags, while most of the models available in the literature are mainly applicable for a limited range of slag composition. Viscosity estimation by this model is close to the experimental value for all types of blast furnace slags. This model is based on the chemical composition of slag and is applicable for slags above liquidus temperature.
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experimental investigation of the viscosities in cao sio2 mgo al2o3 and cao sio2 mgo al2o3 tio2 slags
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2007Co-Authors: Amitabh Shankar, Marten Gornerup, A K Lahiri, Seshadri SeetharamanAbstract:The viscosities of high alumina blast furnace slags were experimentally determined by the rotating cylinder method using the Brookfield digital viscometer model LVDV-II+ pro. Two different slag systems were considered for the current study, the CaO-SiO2-MgO-Al2O3 quaternary and the CaO-SiO2-MgO-Al2O3-TiO2 quinary system. Experiments were conducted in the temperature range of 1650 to 1873 K. The effects of temperature, Basicity, TiO2, and silica activity of slags on viscosity were studied. The viscosity decreases with Basicity for high alumina blast furnace slags with Basicity in the range of 0.46 to 0.8. At high Basicity (∼0.8), slag viscosity decreases even with a small amount of TiO2 (∼2 pct) addition in the slag. With an increase in silica activity in the range of 0.1 to 0.4, the slag viscosity increases, the increases being steeper below the liquidus temperature.
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Phosphorus Partition between Liquid Steel and CaO-SiO2-FeOx-P2O5-MgO Slag Containing 15 to 25 Pct FeO
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2007Co-Authors: Somnath Basu, Ashok Kumar Lahiri, Seshadri SeetharamanAbstract:CaO-SiO2-FeOx-P2O5-MgO bearing slags are typically used in the basic oxygen steelmaking (BOS) process. The partition ratio of phosphorus between slag and steel is an index of the phosphorus holding capacity of the slag, which determines the phosphorus content achievable in the finished steel. The influence of factors such as FeO content and Basicity on the phosphorus partition ratio was investigated at two different temperatures. The partition ratio initially increased with Basicity but remained constant beyond a Basicity of 2.5 to 2.6. An increase in the FeO content up to 18 to 20 mass pct was beneficial for the phosphorus partition at a Basicity level of 2 to 3, but a higher concentration of FeO resulted in a decrease in the phosphorus partition ratio; the FeO concentration corresponding to this transition varied with Basicity and temperature. At even lower basicities, however, the equilibrium phosphorus partition showed either no change, or a marginally decreasing trend, with an increase in the FeO content.
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Phosphorus partition between liquid steel and CaO-SiO2-P2O5-MgO slag containing low FeO
Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science, 2007Co-Authors: Somnath Basu, Ashok Kumar Lahiri, Seshadri SeetharamanAbstract:CaO-SiO2-FeOx-P2O5-MgO bearing slags are typical in the basic oxygen steelmaking (BOS) process. The partition ratio of phosphorus between slag and steel is an index of the phosphorus holding capacity of the slag, which determines the phosphorus content achievable in the finished steel. The influences of FeO concentration and Basicity on the equilibrium phosphorus partition ratios were experimentally determined at temperatures of 1873 and 1923 K, for conditions of MgO saturation. The partition ratio initially increased with Basicity but attained a constant value beyond Basicity of 2.5. An increase in FeO concentration up to approximately 13 to 14 mass pct was beneficial for phosphorus partition.
Suojiag Zhang - One of the best experts on this subject based on the ideXlab platform.
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relationship of Basicity and hydrogen bond properties of ionic liquids with its catalytic performance application to synthesis of propylene glycol methyl ether
Catalysis Communications, 2017Co-Authors: Shengxin Chen, Yajing Li, Ruirui Zhang, Cong Zhao, Hongguo Tang, Congzhen Qiao, Suojiag ZhangAbstract:The relationship of Basicity and hydrogen bond with catalytic performance was investigated in synthesis of propylene glycol methyl ether (PGME) catalyzed by various ILs ([Emim][OAC], [Bmim][OAC], [N2222][OAC], [EtOHN111][OAC], [N4444]Br, [Bmim][N(CN)2], [Bmim]Br, [Bmim][PF6]). The Basicity and Kamlet-Taft parameters of each catalyst were evaluated by UV–visible spectroscopy. It was found the catalytic performance is the synergistic effect of Basicity and hydrogen bond donating ability in the synthesis of PGME from PO and CH3OH, which is quite different from the conventional basic catalytic mechanism.
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relationship of Basicity and hydrogen bond properties of ionic liquids with its catalytic performance application to synthesis of propylene glycol methyl ether
Catalysis Communications, 2017Co-Authors: Shengxin Chen, Ruirui Zhang, Cong Zhao, Hongguo Tang, Congzhen Qiao, Ruixia Liu, Suojiag ZhangAbstract:The relationship of Basicity and hydrogen bond with catalytic performance was investigated in synthesis of propylene glycol methyl ether (PGME) catalyzed by various ILs ([Emim][OAC], [Bmim][OAC], [N2222][OAC], [EtOHN111][OAC], [N4444]Br, [Bmim][N(CN)2], [Bmim]Br, [Bmim][PF6]). The Basicity and Kamlet-Taft parameters of each catalyst were evaluated by UV–visible spectroscopy. It was found the catalytic performance is the synergistic effect of Basicity and hydrogen bond donating ability in the synthesis of PGME from PO and CH3OH, which is quite different from the conventional basic catalytic mechanism.
Ivari Kaljurand - One of the best experts on this subject based on the ideXlab platform.
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Experimental Basicities of Superbasic Phosphonium Ylides and Phosphazenes
The Journal of Organic Chemistry, 2016Co-Authors: Jaan Saame, Agnes Kutt, Ivari Kaljurand, Toomas Rodima, Ilmar A Koppel, Sofja Tshepelevitsh, Tõiv Haljasorg, Ivo LeitoAbstract:Experimental basicities of some of the strongest superbases ever measured (phosphonium ylides) are reported, and by employing these compounds, the experimental self-consistent Basicity scale of superbases in THF, reaching a pKα (estimate of pKa) of 35 and spanning more than 30 pKa units, has been compiled. Basicities of 47 compounds (around half of which are newly synthesized) are included. The solution Basicity of the well-known t-Bu-N═P4(dma)9 phosphazene superbase is now rigorously linked to the scale. The compiled scale is a useful tool for further Basicity studies in THF as well as in other solvents, in particular, in acetonitrile. A good correlation between basicities in THF and acetonitrile spanning 25 orders of magnitude gives access to experimentally supported very high (pKa > 40) basicities in acetonitrile, which cannot be directly measured. Analysis of structure–Basicity trends is presented.
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Experimental Basicities of Phosphazene, Guanidinophosphazene, and Proton Sponge Superbases in the Gas Phase and Solution
2016Co-Authors: Ivari Kaljurand, Jaan Saame, Toomas Rodima, Ivar Koppel, Ilmar A. Koppel, Julius F. Kögel, Jörg Sundermeyer, Uwe Köhn, Martyn P. Coles, Ivo LeitoAbstract:Experimental gas-phase superBasicity scale spanning 20 orders of magnitude and ranging from bicyclic guanidine 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene to triguanidinophosphazenes and P3 phosphazenes is presented together with solution Basicity data in acetonitrile and tetrahydrofuran. The most basic compound in the scaletriguanidinophosphazene Et–NP[NC(NMe2)2]3has the highest experimental gas-phase Basicity of an organic base ever reported: 273.9 kcal mol–1. The scale includes besides the higher homologues of classical superbasic phosphazenes and several guanidino-substituted phosphazenes also a number of recently introduced bisphosphazene and bis-guanidino proton sponges. This advancement was made possible by a newly designed Fourier transform ion cyclotron resonance (ICR) mass spectrometry 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. The obtained experimental gas-phase and solution Basicity data are analyzed in terms of structural and solvent effects and compared with data from theoretical calculations
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experimental gas phase Basicity scale of superbasic phosphazenes
Journal of Physical Chemistry A, 2007Co-Authors: Ivari Kaljurand, Agnes Kutt, Toomas Rodima, Ilmar A Koppel, Masaaki Mishima, Evaingrid Room, Ivar Koppel, Ivo LeitoAbstract:Seventeen superbasic phosphazenes and two Verkade's bases were used to supplement and extend the experimental gas-phase Basicity scale in the superbasic region. For 19 strong bases the gas-phase Basicity values (GB) were determined for the first time. Among them are such well-known bases as BEMP (1071.2 kJ/mol), Verkade's Me-substituted base (1083.8 kJ/mol), Et−NP(NMe2)2-NP(NMe2)3 (Et−P2 phosphazene, 1106.9 kJ/mol), and t-Bu−NP(NMe2)3 (t-Bu−P1 phosphazene, 1058.0 kJ/mol). For the first time experimental GB values were determined for P2 phosphazenes. Together with our previous results self-consistent experimental gas-phase Basicity scale between 1020 and 1107 kJ/mol is now established. This way an important region of the gas-phase Basicity scale, which was earlier dominated by metal hydroxide bases, is now covered also with organic bases making it more accessible for further studies. The GB values for several superbases were calculated using density functional theory at the B3LYP/6-311+G** level. For the p...
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Basicity of some p1 phosphazenes in water and in aqueous surfactant solution
Organic and Biomolecular Chemistry, 2006Co-Authors: Lilli Soovali, Agnes Kutt, Ivari Kaljurand, Toomas Rodima, Ilmar A Koppel, Ivo LeitoAbstract:The pKa values in water and in dilute surfactant solution for 15 ring-substituted phenyl P1 pyrrolidino phosphazenes PhNP(NC4H8)3 and the phenyl P1 dimethylamino phosphazene PhNP(NMe2)3 previously studied in acetonitrile (AN) and tetrahydrofuran (THF) are reported. The nonionic surfactant Tween 20 was used for the Basicity measurements of some compounds to overcome the solubility problems. Measurements with a control group of phosphazenes in both media were used to validate the use of the obtained pKa values as estimates of aqueous values. The pKa values of the studied phosphazenes in aqueous medium vary from 6.82 (2,6-dinitro-) to 12.00 (4-dimethylamino-). The Basicity span is 5.18 pKa units. The aqueous pKa values of the P1 phosphazenes were correlated with the respective Basicity data in AN and THF and from these correlations the pKa values in water for the parent compounds HNP(NC4H8)3 and HNP(NMe2)3 were estimated as 13.9 and 13.3. Also a comparison of the Basicity of phosphazenes and some guanidines, amines and pyridines was made. In water the parent phosphazenes and guanidines are the strongest of all the groups of bases studied. In AN and THF the parent phosphazenes are clearly the strongest bases followed by guanidines, amines and pyridines which are bracketed between the basicities of phenyl phosphazenes. In the gas phase the phosphazenes for which data are available are clearly more basic than the other compounds referred to here. Comparison of the Basicity data of P1 phosphazenes and some guanidines confirms earlier conclusions about the partly ylidic character of the NP double bond.
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acid base equilibria in nonpolar media 4 extension of the self consistent Basicity scale in thf medium gas phase basicities of phosphazenes
Journal of Organic Chemistry, 2003Co-Authors: Ivari Kaljurand, Ivo Leito, Toomas Rodima, Aino Pihl, Vahur Maemets, Ilmar A Koppel, Masaaki MishimaAbstract:Eleven new phenyl-substituted phosphazenes (P1-, P3-, and P4-bases) have been synthesized by the Staudinger or the Kirsanov reactions. The UV−vis spectrophotometric titration method was used to establish the relative Basicity of them, and to extend the ion-pair Basicity scale for THF medium. These measurements together with our previous work give a continuous Basicity scale in THF ranging from 2.6 (2-MeO-pyridine) to 26.6 (2-Cl-C6H4P4(pyrr) phosphazene) in pKα units: that is for 24 orders of magnitude and containing 58 compounds (pyridines, anilines, amines, guanidines, amidines, phosphazenes). Ion-pair formation was taken into account by using the Fuoss equation. ΔpKip values of some phosphazene indicators estimated earlier by the 13C NMR method were revised. For some of the phosphazenes gas-phase basicities were measured.
