Posts Tagged ‘Equilibrium chemistry’
Sunday, January 13th, 2019
Linear free energy relationships (LFER) are associated with the dawn of physical organic chemistry in the late 1930s and its objectives in understanding chemical reactivity as measured by reaction rates and equilibria.
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Tags:Benzoic acid, Chemical IT, Chemical kinetics, chemical reaction, chemical reactivity, chemist, Chemistry, Electrophilic aromatic substitution, energy point, Equations, Equilibrium chemistry, Equilibrium constant, free energy overall route, Hammett equation, Interesting chemistry, Linear free energy relationships, Natural sciences, Organic chemistry, Physical organic chemistry, Physical sciences, Reactivity
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Sunday, April 24th, 2016
The autoionization of water involves two molecules transfering a proton to give hydronium hydroxide, a process for which the free energy of reaction is well known. Here I ask what might happen with the next element along in the periodic table, F.
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Tags:dielectric, energy, Equilibrium chemistry, Fluorides, free energy, free energy barrier, Hydrogen bond, Hydronium, Inorganic solvents, Interesting chemistry, Lithium fluoride, low energy final geometry corresponds, Oxides, PH, Properties of water, Self-ionization of water, Water, Water model
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Thursday, April 14th, 2016
Ammonium hydroxide (NH4+…OH–) can be characterised quantum mechanically when stabilised by water bridges connecting the ion-pairs. It is a small step from there to hydronium hydroxide, or H3O+…OH–. The measured concentrations [H3O+] ≡ [OH–] give rise of course to the well-known pH 7 of pure water, and converting this ionization constant to a free energy indicates that the solvated ion-pair must be some ~19.1 kcal/mol higher in free energy than water itself.♣ So can a quantum calculation reproduce pH7 for water?
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Tags:Acid dissociation constant, Acids, Cations, chemical bonding, energy, Equilibrium chemistry, free energy, General, Hydride, Hydrogen bond, Hydronium, Hydroxide, Interesting chemistry, Physical chemistry, Properties of water, self-ionization energy, Self-ionization of water
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Thursday, January 7th, 2016
This is the third and final study deriving from my Ph.D.[1]. The first two topics dealt with the mechanism of heteroaromatic electrophilic attack using either a diazonium cation or a proton as electrophile, followed by either proton abstraction or carbon dioxide loss from the resulting Wheland intermediate. This final study inverts this sequence by starting with the proton abstraction from an indolinone by a base to create/aromatize to a indole-2-enolate intermediate, which only then is followed by electrophilic attack (by iodine). Here I explore what light quantum chemical modelling might cast on the mechanism.
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References
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B.C. Challis, and H.S. Rzepa, "Heteroaromatic hydrogen exchange reactions. Part VIII. The ionisation of 1,3-dimethylindolin-2-one", Journal of the Chemical Society, Perkin Transactions 2, pp. 1822, 1975. http://dx.doi.org/10.1039/P29750001822
Tags:Arenium ion, Bases, diazo, Diazonium compound, Electrophile, Electrophilic aromatic substitution, Equilibrium chemistry, Fortran, Historical, Indole, light quantum chemical modelling, Metal ions in aqueous solution, Nuclear physics, Simple aromatic rings, Solutions
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