- 行业: Chemistry
- Number of terms: 1965
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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 incorporation of one or more integral molecules of water into another species with or without displacement of one or more other atoms or groups. For example the incorporation of water into the inner ligand sphere of an inorganic complex is an aquation reaction.
Industry:Chemistry
(1) In the traditional sense, "having a chemistry typified by benzene".
(2) The terms aromatic and antiaromatic have been extended to describe the stabilization or destabilization of transition states of pericyclic reactions. The hypothetical reference structure is here less clearly defined, and use of the term is based on application of the Huckel (4n + 2) rule and on consideration of the topology of orbital overlap in the transition state. Reactions of molecules in the ground state involving antiaromatic transition states proceed, if at all, much less easily than those involving aromatic transition states.
Industry:Chemistry
A cyclically conjugated molecular entity with a stability (due to delocalization) significantly greater than that of a hypothetical localized structure (e.g. Kekulé structure) is said to possess aromatic character. If the structure is of higher energy (less stable) than such a hypothetical classical structure, the molecular entity is "antiaromatic".
The most widely used method for determining aromaticity is the observation of diatropicity in the <sup>1</sup>H NMR spectrum.
Industry:Chemistry
The assembling of separate molecular entities into any aggregate, especially of oppositely charged free ions into ion pairs or larger and not necessarily well-defined clusters of ions held together by electrostatic attraction. The term signifies the reverse of dissociation, but is not commonly used for the formation of definite adducts by colligation or coordination.
Industry:Chemistry
The traditional term describing the preferential formation in a chemical reaction of one enantiomer or diastereoisomer over the other as a result of the influence of a chiral feature in the substrate, reagent, catalyst or environment. The term also refers to the formation of a new chiral feature preferentially in one configuration under such influence.
Industry:Chemistry
A one-electron wavefunction describing an electron in the effective field provided by a nucleus and the other electrons present.
Industry:Chemistry
A chemical reaction in which a product (or a reaction intermediate) also functions as catalyst. In such a reaction the observed rate of reaction is often found to increase with time from its initial value.
Industry:Chemistry
A proton (hydron) transfer reaction between two identical molecules (usually a solvent), one acting as a Brønsted acid and the other as a Brønsted base. For example:
<center>2 H<sub>2</sub>O → <sup> </sup>H<sub>3</sub>O<sup>+</sup> + OH<sup>-</sup></center>
Industry:Chemistry
The product of the activities (or, more approximately, concentrations) of the species produced as the result of autoprotolysis. For solvents in which no other ionization processes are significant the term is synonymous with "ionic product". The autoprotolysis constant for water, K<sub>w</sub>, is equal to the product of activities
<center>a(H<sub>3</sub>O<sup>+</sup>)a(OH<sup>-</sup>) = 1.0 x 10<sup>-14</sup> at 25 <sup>o</sup>C.</center>
Industry:Chemistry
