The enols of acetic acid and methyl acetate

1995 ◽  
Vol 73 (9) ◽  
pp. 1395-1398 ◽  
Author(s):  
J. Peter Guthrie ◽  
Zhi Liu
Keyword(s):  
Free Energy ◽  
Acetic Acid ◽  
Methyl Acetate ◽  
Heat Of Formation ◽  
Standard Entropy ◽  
Free Energies ◽  
Average Value ◽  
Boiling Points ◽  
Free Energy Of Formation ◽  
Energy Of Transfer

We have determined the heat of formation of 1,1-dimethoxyethene, ΔHf(l) = −75.56 ± 0.87 kcal mol−1, by measuring the heat of hydrolysis. The heat of vaporization, 8.47 ± 0.10 kcal mol−1, was estimated from the boiling points at various pressures. The standard entropy of gaseous 1,1-dimethoxyethene, 82.02 ± 2. cal deg−1 mol−1, was calculated using frequencies obtained by MO calculations at the 6-31G** level. The free energy of transfer, 1.02 ± 1, was estimated by additivity with allowance for a distant polar interaction. Thus the free energy of formation in aqueous solution, ΔGf(aq) = −37.07 ± 1.48 kcal mol−1, could be calculated. The free energies of hydrolysis for enol ethers appear to be insensitive to structure; we used an average value and so calculated the values of the free energies of formation of the enols of acetic acid and methyl acetate, −67.90 ± 1.67 and −52.48 ± 1.53 kcal mol−1, respectively. These values are in good agreement with other recent evaluations. This method should be applicable to related enols. Keywords: enols, thermodynamics, heat of formation, entropy, ketene acetal.

Thermodynamics of transfer of Ph4C; scaled-particle theory and the Ph4As+/Ph4B− assumption for single ions

1979 ◽  
Vol 57 (15) ◽  
pp. 2004-2009 ◽  
Author(s):  
Michael H. Abraham ◽  
Asadollah Nasehzadeh
Keyword(s):  
Free Energy ◽  
Total Free Energy ◽  
Scaled Particle Theory ◽  
Free Energies ◽  
Particle Theory ◽  
Free Energy Of Transfer ◽  
Enthalpy And Entropy ◽  
Interaction Term ◽  
Energy Of Transfer ◽  
Entropy Of Transfer

Free energies of transfer of Ph4C from acetonitrile to 20 other solvents have been calculated from literature data. The contribution of the cavity term to the total free energy has been obtained from scaled-particle theory and Sinanoglu–Reisse–Moura Ramos theory. It is shown that there is little connection between the cavity term and the total free energy of transfer, and that there must be, in general, a large interaction term. If the latter is important for transfer of Ph4C, we argue that it must also be important for transfer of the ions Ph4As+ and Ph4B−. Previous suggestions that the interaction term is zero for transfer of these two ions are thus seen to be unreasonable. We also show, for six solvents, that the interaction term for Ph4C is very large in terms of enthalpy and entropy, and that scaled-particle theory seems not to apply to transfers of Ph4C between pure organic solvents.The free energy, enthalpy, and entropy of transfer of Ph4As+ = Ph4B− have been calculated by dividing the total transfer values into neutral and electrostatic contributions; reasonable agreement is obtained between calculated and observed values.

Energetics of acetic acid enol in aqueous solution. A new method for thermodynamic estimation

1993 ◽  
Vol 71 (12) ◽  
pp. 2123-2128 ◽  
Author(s):  
J. Peter Guthrie
Keyword(s):  
Aqueous Solution ◽  
Free Energy ◽  
Acetic Acid ◽  
Satisfactory Agreement ◽  
Marcus Theory ◽  
New Method ◽  
Free Energy Of Formation ◽  
Independent Estimate ◽  
Energy Of Formation

A new disproportionation calculation allows the estimation of the free energy of formation of the enol of acetic acid as 65 ± 2 kcal/mol. The value of pKE derived from this free energy, pKE = 21 ± 2, is in satisfactory agreement with information from the literature about rates of exchange. Analysis of the data on rates of exchange of the C-H protons of acetic acid using Marcus theory allows an independent estimate of the enol content. Exchange in acid and in base lead to internally consistent estimates, pKE = 19.3 ± 2.2, which are within the combined uncertainties of the values from the thermodynamic estimate.

Standard thermodynamic transfer functions from water to water + acetone mixtures for a n-nonylcarbon chain attached to different ionic groups

1978 ◽  
Vol 56 (23) ◽  
pp. 2940-2946 ◽  
Author(s):  
Raymond Bury ◽  
Claude Treiner
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Standard Enthalpy ◽  
Transfer Functions ◽  
Mixed Solvents ◽  
Standard Entropy ◽  
Standard Gibbs Free Energy ◽  
Ionic Groups ◽  
Solvent Molecules ◽  
Energy Of Transfer

The standard enthalpy of transfer of trimethyldecylammonium bromide, tetramethylammonium bromide, methyl and decylsodium sulfate have been determined from water to water + acetone mixtures from calorimetric measurements at 298.15 K. The standard entropy function has been calculated using standard Gibbs free energy of transfer data for the same compounds. It is shown that the standard enthalpy and entropy of transfer of a n-nonylhydrocarbon chain attached to the sulfate or to the trimethylammonium groups are quite different whereas the standard Gibbs free energy functions are practically equal in the mixed solvents. It is concluded that the sign of the charge on the ionic groups is responsible for this behaviour and that the influence of this effect extends to a large number of solvent molecules. It is suggested that a similar effect may contribute to the standard enthalpy of so called reference ions: e.g. tetraphenylboron ion casting some doubt on the reliability of these extrathermodynamic approaches at least in mixed solvents, as far as the standard enthalpy function is concerned.

scholarly journals THE FREE ENERGY OF NITROGEN FIXATION BY LIVING FORMS

1927 ◽  
Vol 10 (4) ◽  
pp. 559-573 ◽  
Author(s):  
Dean Burk
Keyword(s):  
Free Energy ◽  
Nitrogen Fixation ◽  
Evolutionary Process ◽  
Hydrogen Gas ◽  
Free Energies ◽  
Free Energy Of Formation ◽  
General Metabolism ◽  
Other Substances ◽  
Nitrogen Ratio ◽  
Oxygen Gas

Fixation of nitrogen even with liberation of energy or free energy, will take place if either oxygen gas or hydrogen gas, or other substances, especially gases, whose standard free energies are close to zero, are involved to form either nitrates, ammonia, or cyanide, not to speak of still other compounds. It has been pointed out that there are two and only two general conditions where nitrogen fixation can require energy. These are, first, if nitrogen reacts with some compound like water with an already high negative free energy of formation and where negligible oxidation of nitrogen would occur; second, if the plant does not take advantage of working at concentrations where the process would yield free energy. If nitrogen fixation is exothermic and free energy-yielding, how is the carbohydrate requirement of nitrogen-fixing organisms to be interpreted? Are the experimental determinations of the carbon to nitrogen ratio purely circumstantial? Is further hope given to those who may experimentally try to narrow this ratio to where the carbon used is only for the carbon requirements of general metabolism, exclusive of fixation? Do not hypotheses concerning the fixation of nitrogen in the evolutionary process, which are based on the conception that energy is required, lose some of their significance? Does it not suggest that perhaps fixation is far more universal than is supposed among living forms, particularly among the higher green plants, and thereby give encouragement to those who may wish to demonstrate this experimentally? Does it not indicate that perhaps the function of fixation is often to obtain energy for use in general metabolism? Is the general carbohydrate metabolism of the fixation forms to be regarded as being merely extremely inefficient? Or most suggestive of all, is the carbohydrate serving some unobserved function?

Comparison of the free energy of transfer of electrolytes, measured with cells without transference, with the sum of the free energies of the corresponding cations and anions with the Owen-cell on standard conditions

1983 ◽  
Vol 36 (10) ◽  
pp. 1997 ◽  
Author(s):  
K Schwabe ◽  
W Hoffmann ◽  
C Queck
Keyword(s):  
Free Energy ◽  
Free Energies ◽  
Liquid Junction Potential ◽  
Liquid Junction ◽  
Ph Values ◽  
Liquid Junction Potentials ◽  
Free Energy Of Transfer ◽  
Energy Of Transfer ◽  
Very High ◽  
Junction Potential

The comparison of S2ΔS1G°tr(E1) with the sum of the values for the corresponding cation and anion S2ΔS1G°tr(Ct+)~S2ΔS1G°tr(X-) (measured) with Owen cells, gained by double extrapolation and by the assumption that the liquid junction potential at 1→0 may be neglected) gives values which differ by not more than ±5%. Most of the investigated acids allow the conclusion that the pH values, measured in cells with transference, and having the same electrodes, give good information on the acidity of the organic solvent and its water mixtures, referred to the standard state in water. That means that the pH, changed to the same H+ concentration in the solvent compared with that in water, is essentially an effect of the free energy of transfer of the hydrogen ion and not of very high liquid junction potentials.

The tetrahedral intermediate from the hydration of N-methylformanilide

1993 ◽  
Vol 71 (12) ◽  
pp. 2109-2122 ◽  
Author(s):  
J. Peter Guthrie ◽  
Jonathan Barker ◽  
Patricia A. Cullimore ◽  
Jinqiao Lu ◽  
David C. Pike
Keyword(s):  
Aqueous Solution ◽  
Free Energy ◽  
Dimethyl Acetal ◽  
Heat Of Formation ◽  
Basic Solution ◽  
Tetrahedral Intermediate ◽  
Rate Determining Step ◽  
Free Energy Of Formation ◽  
Hydrolysis Of ◽  
Energy Of Formation

Heats of hydrolysis of N-methylformanilide dimethyl acetal have been measured in basic solution. The heat of formation of N-methylformanilide was obtained by determining the equilibrium constant in aqueous solution for its formation from formic acid and N-methylaniline as a function of temperature:[Formula: see text]. These data permit the calculation of the heat of formation of N-methylformanilide dimethyl acetal, [Formula: see text]. The free energy of formation of the tetrahedral intermediate in the hydrolysis of N-methylformanilide was calculated by methods we have previously reported. Consideration of the energetics of the intermediates and the known rates of reaction leads to the conclusion that the rate-determining step for alkaline hydrolysis is cleavage of the C—N bond.

The Free Energies of Hydration of Gaseous Ions

1948 ◽  
Vol 1 (4) ◽  
pp. 480 ◽  
Author(s):  
NS Hush
Keyword(s):  
Free Energy ◽  
Water Molecule ◽  
Pure Water ◽  
Free Energies ◽  
The Real ◽  
Free Energy Of Formation ◽  
Energy Of Hydration ◽  
Free Energy Of Hydration ◽  
Molecule Interaction ◽  
Energy Of Formation

Values of hydration energies of individual ions have usually been obtained by division of sums of energies of hydration of pairs of ions, and those calculated by different authors are usually mutually inconsistent. " Experimental " figures, whenever these are quoted, have always been obtained by assuming the truth of theoretical equations whose accuracy has not been independently checked. The distinction between free energy of ion/water-molecule interaction and the real free energy of hydration of a gaseous ion is pointed out, and the importance of Klein and Lange's measurement of the Volta-potential Hg/Hg+ (soln.), which makes possible the direct calculation of real free energies of hydration of individual ions, thus providing a check on theoretical values, is emphasized. Utilizing this value, the equation - ΔFh� = - ΔFf� + ΔFi� + ΔFs�- 103.92 z kcal. (where ΔFs� is the free energy of formation of the gaseous monatomic element, ΔFi� is the free energy of ionization, ΔFf�is the free energy of formation of the aqueous ion, and ΔFh� is the real free energy of hydration of the ion, of valency z, at 298.2� K.) is derived from fundamental considerations. By means of this equation, the real free energies of hydration of 49 ions are calculated, using the most reliable data. It is proposed that these be provisionally accepted as standard values. Several subsidiary values for important ions are calculated indirectly. The difference between ΔFh� and the free energy of ion/water-molecule interaction is discussed in relation to the surface structure of water : a value of -0.30 v. is derived for the X-potential at the surface of pure water, and it is concluded that at the water/gas interface the positive poles of the surface layer are oriented towards the gas phase. The applicability of a modified Born equation in the calculation of free energies of hydration is discussed, and a modified equation is proposed which yields values of ΔFh� for gaseous ions with noble gas structure in excellent agreement with those calculated independently by the method described above.

Impact of salts on the phase separation and thermodynamic properties of mixed nonionic surfactants in absence/attendance of polyvinyl alcohol

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Md Ackas Ali ◽  
Md. Ruhul Amin ◽  
Shamim Mahbub ◽  
Md. Delwar Hossen ◽  
Md. Anamul Hoque ◽  
...  
Keyword(s):  
Free Energy ◽  
Polyvinyl Alcohol ◽  
Aqueous Medium ◽  
Standard Free Energy ◽  
Tween 80 ◽  
Aqueous System ◽  
Standard Entropy ◽  
Thermodynamic Variables ◽  
Delta G ◽  
Energy Of Transfer

Abstract Mixed surfactant systems are used in different applied fields like pharmaceutical formulation rather than single surfactant. Therefore, the determination of the clouding nature of the triton X-100 (TX-100) + Tween 80 (TW-80) mixture was carried out in H2O and polyvinyl alcohol (PVA). In the occurrence of PVA, the cloud point (CP) values of TX-100 initially enhance with enhancing the concentration of PVA and tend to decrease after a certain concentration. For different ratios of TX-100 and TW-80 mixture having the same concentration of both solutions, CP values increase through the decreasing ratios of TX-100 with/without PVA. In the presence of polymer, at higher ratios of TX-100 than TW-80, the CP values are higher in magnitudes in comparison to the aqueous medium but at lower ratios of TX-100, the value of CP are lower in magnitudes in comparison to the aqueous system. The CP values of the TX-100 + TW-80 mixture in the salt system are lower in magnitudes than the aqueous medium in both the absence/presence of PVA. However, a reduction of CP values was obtained to a large extent for Na2SO4 over NaCl in the case of lower volume ratios of TX-100. Various thermodynamic variables (standard free energy ( Δ G c o ${\Delta}{G}_{c}^{o}$ ), standard enthalpy ( Δ H c o ${\Delta}{H}_{c}^{o}$ ), standard entropy ( Δ S c o ${\Delta}{S}_{c}^{o}$ ) change, thermodynamic parameters of transfer (free energy of transfer ( Δ G c , t o ${\Delta}{G}_{c,t}^{o}$ ), and transfer of enthalpies ( Δ H c , t o ${\Delta}{H}_{c,t}^{o}$ )) of phase transition) were also determined.

THERMODYNAMIC PROPERTIES OF SYNTHETIC BASIC ALUMINITE [Al4(OH)10SO4∙5H2O] FROM SOLUBILITY DATA

1980 ◽  
Vol 60 (2) ◽  
pp. 381-384 ◽  
Author(s):  
S. SHAH SINGH
Keyword(s):  
Free Energy ◽  
Standard Free Energy ◽  
Entropy Change ◽  
Heat Of Formation ◽  
Standard Free Energy Change ◽  
Kcal Mole ◽  
Free Energy Of Formation ◽  
Equilibrium Data ◽  
Solubility Equilibrium ◽  
Energy Of Formation

From the solubility equilibrium data of basic aluminite at three temperatures, the standard free energy change (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) were determined as 160.02 kcal∙mole−1, 65.48 kcal∙mole−1 and 317.1 cal∙deg−1]mole−1, respectively. From these values the free energy of formation (ΔGf°) and the heat of formation (ΔHf°) of basic aluminite was also computed and was 1465.25 kcal∙mole−1 and 1682.08 kcal∙mole−1, respectively.

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