- 行业: 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 ...
A quantitative measure of Lewis basicity devised by Gutmann (1976).
Industry:Chemistry
The decrease in Gibbs energy on going from the reactants to the products of a chemical reaction (-ΔG).
Industry:Chemistry
The decrease in Gibbs energy on going from the reactants to the products of a chemical reaction (-ΔG).
Industry:Chemistry
In a general sense, this is any equation which expresses substituent effects in terms of two parameters. However, in practice the term is used more specifically for an equation for summarizing the effects of meta- or para-substituents (i = m or p) X on chemical reactivity, spectroscopic properties, etc. of a probe site Y in benzene or other aromatic system.
<center>P<sup>i</sup> = ρ<sub>I</sub><sup>i</sup>σ<sub>I</sub> + ρ<sub>R</sub><sup>i</sup>σR</center>
P is the magnitude of the property Y for substituent X, expressed relative to the property for X=H; σ<sub>I</sub> and σ<sub>R</sub> are inductive or polar and resonance substituent constants, respectively, there being various scales for σ<sub>R</sub>; ρ<sub>I</sub> and ρ<sub>R</sub> are the corresponding regression coefficients.
Industry:Chemistry
Change in effective charge is a quantity obtained by comparison of the polar effect of substituents on the free energies of rate or equilibrium processes with that on a standard ionization equilibrium. Provided the effective charge on the states in the standard equilibrium are defined, then it is possible to measure effective charges for states in the reaction or equilibrium under consideration.
Industry:Chemistry
The ratio of the first-order rate constant of an intramolecular reaction involving two functional groups within the same molecular entity to the second-order rate constant of an analogous intermolecular elementary reaction. This ratio has the dimension of concentration. The term can also apply to an equilibrium constant.
Industry:Chemistry
The ratio of the first-order rate constant of an intramolecular reaction involving two functional groups within the same molecular entity to the second-order rate constant of an analogous intermolecular elementary reaction. This ratio has the dimension of concentration. The term can also apply to an equilibrium constant.
Industry:Chemistry
An electron-counting rule to which an overwhelming majority of stable diamagnetic transition metal complexes adhere. The number of nonbonded electrons at the metal plus the number of electrons in the metal-ligand bonds should be 18. The 18 electron rule in transition metal chemistry is a full analogue of the "Lewis octet rule".
Industry:Chemistry
A leaving group that does not carry away the bonding electron pair. For example, in the nitration of benzene by NO<sub>2</sub><sup>+</sup>, H<sup>+</sup> is the electrofuge. The adjective of electrofuge is electrofugal.
Industry:Chemistry
(1) A substance to which an electron may be transferred; for example 1,4-dinitrobenzene or the dication 1,1'-dimethyl-4,4'-bipyridyldiium .
+ (2) A Lewis acid. This usage is discouraged.
Industry:Chemistry
