- Settore: 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 term designates structures in which a hydrogen atom is bonded to both a carbon atom and a metal atom. The term is also used to characterize the interaction between a CH bond and an unsaturated metal center, and to describe similar bonding of a transition metal with Si-H compounds. The expression "μ-hydrido-bridged" is also used to describe the bridging hydrogen.
Industry:Chemistry
A substitution reaction occurring at position 1/ of an allylic system, the double bond being between positions 2/ and 3/. The incoming group may be attached to the same atom 1/ as the leaving group, or the incoming group becomes attached at the relative position 3/, with movement of the double bond from 2/3 to 1/2. For example:
<center>CH<sub>3</sub>CH=CHCH<sub>2</sub>Br → CH<sub>3</sub>CH=CHCH<sub>2</sub>OAc</center>
or
<center>CH<sub>3</sub>CH=CHCH<sub>2</sub>Br → CH<sub>3</sub>CH(OAc)CH=CH<sub>2</sub></center>
(written as a transformation).
Industry:Chemistry
A compound containing a large organic cation or anion which possesses a long unbranched hydrocarbon chain, e.g.
<blockquote>H<sub>3</sub>C(CH<sub>2</sub>)<sub>n</sub>CO<sub>2</sub><sup>-</sup>M<sup>+</sup><br> H<sub>3</sub>C(CH<sub>2</sub>)<sub>n</sub>SO<sub>3</sub><sup>-</sup>M<sup>+</sup><br> H<sub>3</sub>C(CH<sub>2</sub>)<sub>n</sub>N(CH<sub>3</sub>)<sub>3</sub><sup>+</sup>X<sup>-</sup><br> (n > 7).</blockquote>
The existence of distinct polar (hydrophilic) and non polar (hydrophobic) regions in the molecule promotes the formation of micelles in dilute aqueous solution.
Industry:Chemistry
Self-ionizing solvent possessing both characteristics of Brønsted acids and bases, for example H<sub>2</sub>O and CH<sub>3</sub>OH, in contrast to aprotic solvent.
Industry:Chemistry
A chemical species that behaves both as an acid and as a base is called amphoteric. This property depends upon the medium in which the species is investigated: H<sub>2</sub>SO<sub>4</sub> is an acid when studied in water, but becomes amphoteric in superacids.
Industry:Chemistry
A rearrangement in which the migrating group moves with its electron pair from one atom to another.
Industry:Chemistry
Alternative, but less desirable term for annulation. The term is widely used in German and French language.
Industry:Chemistry
A transformation involving fusion of a new ring to a molecule via two new bonds.
Some authors use the term "annelation" for the fusion of an additional ring to an already existing one, and "annulation" for the formation of a ring from one or several acyclic precursors, but this distinction is not made generally.
Industry:Chemistry
Mancude (i.e. having formally the maximum number of noncumulative double bonds) monocyclic hydrocarbon without side chains of the general formula C<sub>n</sub>H<sub>n</sub> (n is an even number) or C<sub>n</sub>H<sub>n+1</sub> (n is an odd number). Note that in systematic nomenclature an annulene with seven or more carbon atoms may be named (n)annulene, where n is the number of carbon atoms, e.g. (9)annulene for cyclonona-1,3,5,7-tetraene.
Industry:Chemistry
Non-protogenic (in a given situation). (With extremely strong Brønsted acids or bases, solvents that are normally aprotic may accept or lose a proton. For example, acetonitrile is in most instances an aprotic solvent, but it is protophilic in the presence of concentrated sulfuric acid and protogenic in the presence of potassium tert-butoxide. Similar considerations apply to benzene, trichloromethane, etc.)
Industry:Chemistry
