- Settore: Chemistry
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The International Union of Pure and Applied Chemistry (IUPAC) serves to advance the worldwide aspects of the chemical sciences and to contribute to the application of chemistry in the service of people and the environment. As a scientific, international, non-governmental and objective body, IUPAC ...
The negative of the Gibbs energy (ΔG<sub>r</sub><sup>o</sup>) change for the reaction
<center>A-H → A<sup>-</sup> + H<sup>+</sup></center>
in the gas phase.
Industry:Chemistry
The negative of the Gibbs energy (ΔG<sub>r</sub><sup>o</sup>) change associated with the reaction
<center>B + H<sup>+</sup> → BH<sup>+</sup></center>
in the gas phase. Also called absolute or intrinsic basicity.
Industry:Chemistry
Pair of molecular entities in close proximity in solution within a solvent cage and resulting from reaction (e.g. bond scission, electron transfer, group transfer) of a precursor that constitutes a single kinetic entity.
Industry:Chemistry
The catalysis of a chemical reaction by a series of Brønsted acids (which may include the solvated hydrogen ion) so that the rate of the catalyzed part of the reaction is given by Σk<sub>HA</sub>(HA) multiplied by some function of substrate concentrations. (The acids HA are unchanged by the overall reaction.) General catalysis by acids can be experimentally distinguished from specific catalysis by hydrogen cations (hydrons) by observation of the rate of reaction as a function of buffer concentration.
Industry:Chemistry
The catalysis of a chemical reaction by a series of Brønsted bases (which may include the lyate ion) so that the rate of the catalyzed part of the reaction is given by Σk<sub>B</sub>(B) multiplied by some function of substrate concentration.
Industry:Chemistry
The standard Gibbs energy difference between the transition state of a reaction (either an elementary reaction or a stepwise reaction) and the ground state of the reactants. It is calculated from the experimental rate constant k via the conventional form of the absolute rate equation:
<center>Δ<sup>†</sup>G = RT (ln(k<sub>B</sub>/h) - ln(k/T))</center>
where k<sub>B</sub> is the Boltzmann constant and h the Planck constant (k<sub>B</sub>/h = 2.08358 x 10<sup>10</sup> K<sup>-1</sup> s<sup>-1</sup>). The values of the rate constants, and hence Gibbs energies of activation, depend upon the choice of concentration units (or of the thermodynamic standard state).
Industry:Chemistry
The standard Gibbs energy difference between the transition state of a reaction (either an elementary reaction or a stepwise reaction) and the ground state of the reactants. It is calculated from the experimental rate constant k via the conventional form of the absolute rate equation:
<center>Δ<sup>†</sup>G = RT (ln(k<sub>B</sub>/h) - ln(k/T))</center>
where k<sub>B</sub> is the Boltzmann constant and h the Planck constant (k<sub>B</sub>/h = 2.08358 x 10<sup>10</sup> K<sup>-1</sup> s<sup>-1</sup>). The values of the rate constants, and hence Gibbs energies of activation, depend upon the choice of concentration units (or of the thermodynamic standard state).
Industry:Chemistry
A defined linked collection of atoms or a single atom within a molecular entity. This use of the term in physical organic and general chemistry is less restrictive than the definition adopted for the purpose of nomenclature of organic compounds.
Industry:Chemistry
The linear free energy relation
<center>log(k<sub>s</sub>/k<sub>0</sub>) = mY</center>
expressing the dependence of the rate of solvolysis of a substrate on ionizing power of the solvent. The rate constant k0 applies to the reference solvent (ethanol-water, 80:20, v/v) and ks to the solvent s, both at 25 <sup>o</sup>C. The parameter m is characteristic of the substrate and is assigned the value unity for tert-butyl chloride. The value Y is intended to be a quantitative measure of the ionizing power of the solvent s. The equation was later extended by Winstein, Grunwald and Jones (1951) to the form
<center>log(k<sub>s</sub>/k<sub>0</sub>) = mY + lN</center>
where N is the nucleophilicity of the solvent and l its susceptibility parameter. The equation has also been applied to reactions other than solvolysis.
Industry:Chemistry
