The toxicity of ammonia to fishes has been attributed to the un-ionized ammonia chemical species present in aqueous solution Because the percent of total ammonia present as un-ionized ammonia (NH3) is so dependent upon pH and temperature, an exact understanding of the aqueous ammonia equilibrium is important for toxicity studies A critical evaluation of the literature data on the ammonia–water equilibrium system has been carried out Results of calculations of values of pKa at different temperatures and of percent of NH3 in aqueous ammonia solutions of zero salinity as a function of pH and temperature are presented

Aqueous Ammonia Equilibrium Calculations: Effect of pH and Temperature

Calculation of the thermodynamic and transport properties of aqueous species at high pressures and temperatures: Standard partial molal properties of organic species

Basen sind nach Losungsmitteln wohl die wichtigste Klasse von Hilfsstoffen fur die organische Synthase. Ihre Funktion ist oft nicht auf die diffusions-kontrollierte Protonen-Aufnahme beschrankt; gerade bei Reaktionen mit starken Metallbasen spielen strukturbestimmende Faktoren, wie Koordinations-Verhalten des Metall-Ions oder Aggregations-Verhalten des metallierten Substrats, eine oft entscheidende, wenn auch ebenso oft unzureichend verstandene, haufig gar unerwunschte Rolle.

Starke ungeladene Stickstoffbasen

The dissociation constants of protonated 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-methyl-1-propanol, diethylmonoethanolamine, diisopropanolamine, dimethylmonoethanolamine, monoethanolamine, 1-amino-2-propanol, methylmonoethanolamine, triethanolamine, and the first and the second dissociation constants of piperazine and hydroxyethylpiperazine have been determined by electromotive force measurements from (293 to 353) K. The dissociation constants of protonated triethylamine have been determined with the same technique from (293 to 333) K. The experimental results and derived values of the standard state thermodynamic properties are reported and compared to available literature values.

Dissociation Constants and Thermodynamic Properties of Amines and Alkanolamines from (293 to 353) K

Publisher Summary This chapter focuses on entropies of activation and mechanisms of reactions in solution Entropy of activation is implied in the transition state theory An underlying principle of the theory is that there exists along the reaction path of any reaction a state of critical energy, the minimum energy of which must be supplied to the reactants in order to cause reaction to occur This state is termed the transition state or activated complex, and the basic Eyring proposal is that it can be treated as a normal molecule with respect to its thermodynamic properties Determination of both the energy (and enthalpy) of activation and the entropy of activation involves measurement of the temperature coefficient of the rate constant Although possessing certain inherent limitations, transition state theory seems adequate to permit the quantitative computation of kinetic parameters from first principles Practical application of the theory is impeded by incomplete information about the molecular properties of the activated complex and, for reactions in solution, the lack of a quantitative description of molecular interactions in condensed phases Because transition state theory is essentially an equilibrium theory, one basis for comparison is thermodynamic data for solution equilibria From the inception of transition state theory, entropies of activation are from the twin aspects of molecular structure and reaction mechanism in this chapter

Entropies of Activation and Mechanisms of Reactions in Solution

The thermodynamic acid dissociation constants of n-propylammonium, n-butylammonium, and triethylammonium ions in water have been measured by use of an e.m.f. technique over the temperature range 0–50°. The results have been used to calculate values of ΔG°, ΔH°, ΔS°, and ΔCp° for the equilibria: BH++ H2O B + H3O+. The values obtained, together with data on other ammonium ions, are discussed in relation to the structure of the neutral amine molecules, the structure of the ions, and the interaction of the solute species with the structure of liquid water.

The thermodynamics of the acid dissociation of some alkylammonium ions in water

A redetermination of the dissociation constant of the ammonium ion and the base strength of ammonia in water

The dissociation constants of the following fatty acids have been determined in water relative to acetic acid over the temperature range 0 to 60° C: propionic, n-valeric, n-hexoic, itfo-butyrie, iso-valeric, iso-hexoic, trimethylacetic, diethylacetic. Using Hamed’s data for acetic acid as standard, the individual dissociation constants have been evaluated. The available data for the fatty acids are analyzed to obtain the heats of ionization, and the entropy and heat capacity changes of ionization. These quantities are discussed in relation to the structure of the acid and the orientation of water molecules by the ions. It is conducted that the ions influence the water structure in a volume round the ionic charge of radius about 5 A, and that the effect of the ionic charge on the rigidity of the hydrocarbon chain and on the solvent structure both play an important part in determining the efatropy and heat capacity changes.

D. H. Everett

Papers

The thermodynamics of the acid dissociation of some alkylammonium ions in water

A redetermination of the dissociation constant of the ammonium ion and the base strength of ammonia in water

The thermodynamics of ionization of some fatty acids