Thermodynamics of methanesulfonic acid revisited

2000 ◽  
Vol 78 (10) ◽  
pp. 1295-1298 ◽  
Author(s):  
J Peter Guthrie ◽  
Roger T Gallant
Keyword(s):  
Methanesulfonic Acid ◽  
Heat Of Formation ◽  
Methyl Methanesulfonate ◽  
Thermodynamic Quantities ◽  
Heat Of Reaction ◽  
Reaction Conditions ◽  
Free Energy Of Formation ◽  
Sulfite Ion ◽  
Energy Of Formation

Recently we reported a study of the thermodynamics of methanesulfonic acid and some of its derivatives. The foundation of these results was a measurement of the heat of reaction of S-methyl thioacetate with aq sodium hypochlorite, leading to methanesulfonic acid. We have reinvestigated this reaction and discovered that contrary to the initial stoichiometry experiments, the stoichiometry under the reaction conditions is not as was believed and that the heat of reaction observed was spuriously high. We have found a new reaction, that of sulfite ion with methyl methanesulfonate, which does allow a clean determination of the heat of formation of methanesulfonic acid. Revised thermodynamic quantities for methanesulfonic acid, methanesulfonyl chloride, and methyl methanesulfonate are reported here.Key words: sulfonic acid, heat of reaction, free energy of formation, SN2 reaction.

Thermodynamics of methanesulfonic acid, methanesulfonyl chloride, and methyl methanesulfonate

1998 ◽  
Vol 76 (6) ◽  
pp. 929-936 ◽  
Author(s):  
J Peter Guthrie ◽  
Allan R Stein ◽  
Anthony P Huntington
Keyword(s):  
Aqueous Solution ◽  
Methanesulfonic Acid ◽  
Heat Of Formation ◽  
Methyl Methanesulfonate ◽  
Molecular Orbital Calculations ◽  
Heat Of Reaction ◽  
Free Energies ◽  
Methanesulfonyl Chloride ◽  
Free Energy Of Formation ◽  
Energy Of Formation

The heat of formation of liquid methanesulfonic acid, -178.09 ± 1.48, was determined by measuring the heat of reaction of methyl thiolacetate with aqueous hypochlorite solution to give aqueous methanesulfonate and acetate. The heats of formation of liquid methanesulfonyl chloride, -126.91 ± 1.54, and methyl methanesulfonate, -164.34 ± 1.58, were determined by measuring the heats of reaction of methanesulfonyl chloride with water or methanol in the presence of a suitable basic catalyst. Heats of vaporization (based on vapor-pressure data), entropies (based on ab initio molecular orbital calculations), and free energies of transfer from gas phase to aqueous solution were calculated leading to values for the free energies of formation in aqueous solution. The free energies of formation so determined were methanesulfonic acid, -151.72 ± 2.68, methanesulfonyl chloride, -101.29 ± 1.96, and methyl methanesulfonate, -127.28 ± 2.08. From these values the free energies of hydrolysis (leading to unionized methanesulfonic acid) are methanesulfonyl chloride, -25.11 ± 3.04, and methyl methanesulfonate, -9.90 ± 2.48.Key words: sulfonic acids, heat of formation, free energy of formation, hydrolysis.

Heat Capacity, Entropy, and Free Energy of Rubber Hydrocarbon

1936 ◽  
Vol 9 (2) ◽  
pp. 264-274 ◽  
Author(s):  
Norman Bekkedahl ◽  
Harry Matheson
Keyword(s):  
Heat Capacity ◽  
Free Energy ◽  
Heat Of Formation ◽  
The Third ◽  
Free Energy Of Formation ◽  
Third Law Of Thermodynamics ◽  
Third Law ◽  
Lower Temperature ◽  
Energy Of Formation

Abstract The best method for obtaining the free energy of formation of rubber is by making use of the third law of thermodynamics. This makes necessary the determination of heat-capacity values of rubber from room temperature down to temperatures sufficiently low to apply an empirical formula for obtaining the values below this lower temperature. From these heat-capacity values the entropy may be obtained. Then from this latter value, along with the entropy values of carbon (graphite) and gaseous hydrogen and the heat of formation of rubber, a reliable value for the free energy of formation of rubber may be calculated. Several investigators have previously determined the heat capacities of rubber, but their observations were not made at temperatures sufficiently low to permit accurate extrapolation to the absolute zero in order to apply the third law. Furthermore, in the previous work the possibility that rubber at low temperatures might exist either as a metastable amorphous form or as a crystalline form was not clearly recognized. In the present investigation the aim was not only to extend the temperature range but also to obtain data of a higher order of accuracy than that previously reported.

High Temperature Electrochemical Determination of the Thermodynamic Stability of the Iron-Rich, Iron-Niobium Intermetallic Phase

1969 ◽  
Vol 24 (10) ◽  
pp. 1580-1585 ◽  
Author(s):  
Giovanni B. Barbi
Keyword(s):  
Free Energy ◽  
Intermetallic Phase ◽  
Standard Free Energy ◽  
Chemical Oxidation ◽  
Electrochemical Determination ◽  
Electrolytic Cell ◽  
Galvanic Cells ◽  
Free Energy Of Formation ◽  
Energy Of Formation

Abstract A non-stationary technique of e.m.f. measurements after polarization of solid galvanic cells, previously applied to the determination of the standard free energy of formation of metal oxides, has been extended to intermetallic phases. The chief condition of applicability of this technique to intermetallic compounds is that the rates of recombination of the cathodic reduction products to yield the stable intermetallic phase be high as compared with that of chemical oxidation at the interface with the solid intermediate electrolyte, due to oxygen impurities in the gas phase. In particular, the solid electrolytic cell:(y values expressing the ε-phase iron-rich boundary compositions according to different authors investigations) was examined.Values of the standard free energy of formation of Fe7-yNb2 from the elements, ranging between-3.77+0.72-10-3 T and -5.66+1.09 · 10-3 T kcal/atom were found.

Tautomeric equilibria and pKa values for 'sulfurous acid' in aqueous solution: a thermodynamic analysis

1979 ◽  
Vol 57 (4) ◽  
pp. 454-457 ◽  
Author(s):  
J. Peter Guthrie
Keyword(s):  
Aqueous Solution ◽  
Free Energy ◽  
Aqueous Solutions ◽  
Equilibrium Constants ◽  
Acid Solutions ◽  
Sulfurous Acid ◽  
Free Energy Of Formation ◽  
Dilute Aqueous Solutions ◽  
Sulfite Ion ◽  
Energy Of Formation

The free energy of formation of dimethyl sulfite in aqueous solution can be calculated as −91.45 ± 0.79 kcal/mol; this calculation required measurement of the solubility of dimethyl sulfite. From this value and the pKa of SO(OH)2, using previously reported methods, the free energy of formation of SO(OH)2 can be calculated to be −129.26 ± 0.89 kcal/mol. Comparison of this value with the value obtained from the free energy of formation of 'sulfurous acid' solutions, calculated from the free energy of formation of sulfite ion and the apparent pKa, values, permits evaluation of the free energy of covalent hydration of SO2 as 1.6 + 1.0 kcal/mol, in agreement with earlier qualitative spectroscopic observations. From the apparent pKa and the anticipated pKa values for the tautomers (SO(OH)2, pK1 = 2.3; HSO2(OH), pK1 = −2.6) it is possible to calculate the free energy change for tautomerization of SO(OH)2 to H—SO2(OH) as +4.5 ± 1.2 kcal/mol. All equilibrium constants required for Scheme 1, describing the species present in dilute aqueous solutions of SO2, have been calculated. In agreement with previous Raman studies the major tautomer of 'bisulfite ion' is calculated to be H—SO3−.

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