The trifluoroacetic acid solvent system. Part V. Cryoscopic measurements

Measurement of freezing point depressions for the non-electrolytes, CCl4. CH3SO2F, and (CF3CO)2O permit calculation of the cryoscopic constant for trifluoroacetic acid, HOTFA. Water is shown to give freezing point depressions lower than those for non-electrolytes and this is attributed to association. Freezing point depressions for NaOTFA, KOTFA, and CsOTFA have been measured and accounted for in terms of ion-pair dissociation constants previously determined from electrical conductivity measurements. The results cast doubt on the existence of triple ions in this solvent.

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The Trifluoroacetic Acid Solvent System. Part IV. Triple Ions

Canadian Journal of Chemistry ◽

10.1139/v72-599 ◽

1972 ◽

Vol 50 (23) ◽

pp. 3789-3798 ◽

Cited By ~ 3

Author(s):

M. G. Harriss ◽

J. B. Milne

Keyword(s):

Trifluoroacetic Acid ◽

Dissociation Constants ◽

Solvent System ◽

Solute Concentration ◽

Ion Pair ◽

Ionic Charge ◽

System Part ◽

Triple Ions ◽

Ion Size ◽

Triple Ion

Electrolytes studied in 100% trifluoroacetic acid exhibit a minimum in equivalent conductivity with increasing solute concentration. This behavior is accounted for by the formation of triple-ions at higher concentrations. Triple-ion dissociation constants, k, have been evaluated and, in general, they show the opposite trend with changing ion size to that of the ion-pair dissociation constants; that is the triple-ions of smaller ions are more dissociated. The experimentally observed trend is accounted for by using a partial ionic charge instead of unit charge for the ion-pair charges in the theoretical Fuoss expression for k.The excellent extrapolation of the triple-ion data to give a value of Λ0Kd for the ion-pair, which agrees well with that determined from a Fuoss plot, permits an estimate of Λ0 for LiO2CCF3 from the triple-ion data.

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The trifluoroacetic acid solvent system. Part VI. Density measurements

Canadian Journal of Chemistry ◽

10.1139/v80-045 ◽

1980 ◽

Vol 58 (3) ◽

pp. 283-286 ◽

Cited By ~ 2

Author(s):

John B. Milne

Keyword(s):

Trifluoroacetic Acid ◽

Dissociation Constants ◽

Ion Pairs ◽

Solvent System ◽

Apparent Molar Volumes ◽

Equivalent Conductivity ◽

Molar Volumes ◽

Density Measurements ◽

System Part ◽

Triple Ions

The densities of solutions of several 1:1 trifluoroacetate electrolytes have been measured in 100% trifluoroacetic acid (HOTFA) and apparent molar volumes for their ion pairs have been determined. The density measurements coupled with limiting equivalent conductivities and dissociation constants, calculated by means of the Fuoss–Hsia equation, permit a more precise treatment of the conductivities of solutions at concentrations where the equivalent conductivity minimum occurs. The existence of triple ions in this solvent is not required to account for the conductivity minimum.

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THE SULPHURIC ACID SOLVENT SYSTEM: PART I. ACID-BASE REACTIONS

Canadian Journal of Chemistry ◽

10.1139/v60-190 ◽

1960 ◽

Vol 38 (8) ◽

pp. 1363-1370 ◽

Cited By ~ 20

Author(s):

R. H. Flowers ◽

R. J. Gillespie ◽

E. A. Robinson

Keyword(s):

Electrical Conductivity ◽

Sulphuric Acid ◽

Dissociation Constants ◽

Solvent System ◽

Conductivity Measurements ◽

Acid Base ◽

Acid And Base ◽

System Part ◽

Acids And Bases ◽

Good Agreement

Acid–base reactions in the solvent sulphuric acid are discussed. Such reactions are conveniently studied by electrical conductivity measurements. A relation between the composition at which the conductivity has a minimum value and the strengths of the acid and base is derived. Values of the dissociation constants of acids and bases obtained in this way are shown to be in good agreement with values obtained by other methods.

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THE SULPHURIC ACID SOLVENT SYSTEM: PART II. CONDUCTIVITY MEASUREMENTS ON SOLUTIONS OF SOME ACIDS

Canadian Journal of Chemistry ◽

10.1139/v61-160 ◽

1961 ◽

Vol 39 (6) ◽

pp. 1266-1273 ◽

Cited By ~ 31

Author(s):

J. Barr ◽

R. J. Gillespie ◽

E. A. Robinson

Keyword(s):

Dissociation Constant ◽

Sulphuric Acid ◽

Dissociation Constants ◽

Solvent System ◽

Acid Dissociation ◽

Acid System ◽

Conductivity Measurements ◽

Acid Dissociation Constants ◽

Strong Base ◽

System Part

Conductivity measurements have been made on solutions of the following substances in sulphuric acid: HClO4, HSO3F, HSO3Cl, HPO2F2, HAs(HSO4)4, CH3SO3H, and CF3CO2H. Of these substances HSO3F, HSO3Cl, HAs(HSO4)4, and probably HClO4, behave as acids, CF3CO2H is a non-electrolyte, and HPO2F2, and probably CH3SO3H, are bases of the sulphuric acid system. Acid dissociation constants for HSO3F, HSO3Cl, and HAs(HSO4)4 have been determined by comparing the conductivities of their solutions with those of H2S2O7, whose dissociation constant is known from other measurements, and also by conductimetric titration with a strong base, e.g. KHSO4. These acids of the sulphuric acid system decrease in strength in the order HSO3F > HAs(HSO4)4 > HSO3Cl > HClO4.

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The Trifluoroacetic Acid Solvent System. Part III. The Acid, HB(OOCCF3)4, and the Solvent Autoprotolysis Constant

Canadian Journal of Chemistry ◽

10.1139/v71-604 ◽

1971 ◽

Vol 49 (22) ◽

pp. 3612-3616 ◽

Cited By ~ 8

Author(s):

M. G. Harriss ◽

J. B. Milne

Keyword(s):

Trifluoroacetic Acid ◽

Solvent System ◽

System Part

The limiting equivalent conductivities, Λ0, of the acids, HB(OOCCF3)4 and HSbF5(OOCCF3), and the salt, CsB(OOCCF3)4, have been measured and found to be 22.34, 18.77, and 48.56 ohm−1 cm2 equiv−1, respectively. Calculation of the solvent autoprotolysis constant gives the value: 4 × 10−14 mol2 l−2. The salt, CsB(OOCCF3)4 is readily prepared but the parent acid, B(OOCCF3)3 could not be isolated.

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The Trifluoroacetic Acid Solvent System. Part II. Acids

Canadian Journal of Chemistry ◽

10.1139/v71-491 ◽

1971 ◽

Vol 49 (18) ◽

pp. 2937-2942 ◽

Cited By ~ 7

Author(s):

M. G. Harriss ◽

J.B Milne

Keyword(s):

Nuclear Magnetic Resonance ◽

Magnetic Resonance ◽

Trifluoroacetic Acid ◽

Solvent System ◽

Fluoroacetic Acid ◽

Mixed Anhydrides ◽

System Part ◽

Nuclear Magnetic

19F nuclear magnetic resonance (n.m.r.) studies show that SbF5 forms HSbF5(OOCCF3) in tri-fluoroacetic acid. This complex acid does not react with (CF3CO)2O which must be added to carry out conductimetric studies in anhydrous HOOCCF3. However, HClO4, HSO3F, and HNO3 all react with (CF3CO)2O to yield mixed anhydrides CF3COClO4, CF3COSO3F, and NO2OOCCF3. HBF4 reacts with the anhydride to give CF3COF while H2SO4 appears to be simply dehydrated to polysulfuric acids.

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The chlorosulfuric acid solvent system. Part II. The solutes SeCl4 and TeCl4; evidence for the formation of the SeCl3+ and TeCl3+ ions

Canadian Journal of Chemistry ◽

10.1139/v68-530 ◽

1968 ◽

Vol 46 (20) ◽

pp. 3197-3200 ◽

Cited By ~ 6

Author(s):

E. A. Robinson ◽

J. A. Ciruna

Keyword(s):

Electrical Conductivity ◽

Raman Spectra ◽

Vibrational Spectra ◽

Strong Acid ◽

Ionic Species ◽

Solvent System ◽

Acid Solutions ◽

Conductivity Measurements ◽

System Part

From the results of electrical conductivity measurements on solutions in chlorosulfuric acid and the Raman spectra of solutions in chlorosulfuric acid (and fluorosulfuric acid) it is shown that SeCl4 and TeCl4 ionize quantitatively in these strong acid solutions to give the SeCl3+ and TeCl3+ cations.By comparison of the spectra with the vibrational spectra of solid SeCl4 and solid TeCl4, reported by other workers, it is suggested that the solids contain covalent MCl4 molecules rather than the ionic species MCl3+•Cl−, suggested previously.

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The Trifluoroacetic Acid Solvent System. Part I. Bases

Canadian Journal of Chemistry ◽

10.1139/v71-307 ◽

1971 ◽

Vol 49 (11) ◽

pp. 1888-1894 ◽

Cited By ~ 8

Author(s):

M. G. Harriss ◽

J. B. Milne

Keyword(s):

Electrical Conductivity ◽

Alkali Metal ◽

Proton Transfer ◽

Trifluoroacetic Acid ◽

Ionic Mobility ◽

Solvent System ◽

Association Constants ◽

Metal Trifluoroacetates ◽

Cation Radius ◽

System Part

Electrical conductivity has been used to study the ionic behavior of several simple solutes in 100% trifluoroacetic acid. Fuoss extrapolations have been used to evaluate the limiting equivalent conductivities and association constants of the ammonium and alkali metal trifluoroacetates. The dependence of ionic mobility upon cation radius is different from that in water and other solvents and suggests that solvation is much less important in 100% trifluoroacetic acid. On the basis of these results, a proton transfer mechanism of conductance for the trifluoroacetate ion appears unlikely.

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