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(organic chemistry)
CO(CHCH)2CO Yellow crystalline compound with irritating aroma; melts at 116°C; soluble in alcohol, alkalies, and ether; used to make dyes and hydroquinone. Also known as benzoquinone; chinone.



any one of a class of cyclic diketones in which both carbonyl (C=O) groups are in a system of conjugated double bonds. Quinones are obtained in the form of colored crystals, which have a sharp odor. For example, para-benzoquinone (I), with a melting point of 116°C, and 1,4-naphthoquinone (II), with a melting point of 128.5°C, are yellow, while ortho-benzoquinone (III), with a melting point of 70°–80°C (with decomposition), and anthraquinone are red (seeANTHRAQUINONE).

Various pigments in nature are derivatives of quinones; for example, muscapharin, the dye substance of the fly agaric, is a derivative of para-benzoquinone. Quinones are readily reduced to yield diatomic phenols [for example, in industry, hydroquinone is obtained from (I) in this way]. They actively enter in diene synthesis,

as well as form molecular complexes with phenols. They are used in analytical chemistry.

Quinones are obtained by several methods, including the oxidation of the aromatic hydrocarbons or of their hydroxy or amino derivatives; for example, (I) is obtained by the oxidation of aniline, while (II) and anthraquinone are obtained by the oxidation of naphthalene and anthracene, respectively. Quinones and their derivatives are intermediate products in the production of dyes (seeANTHRAQUINONE DYES). They are also used as fungicides, insecticides, and tanning agents. 2-Methyl-1,4-naphthoquinone is a vitamin of the vitamin K group.

References in periodicals archive ?
From FTIR spectroscopes, HCl are reacted physically with PANI causing a shift in the quinoid ring and benzoid ring peaks and the increasing in applied voltage cause increasing in the intensity.
5 to 4 ppm are assigned to the protons of the methoxy groups on the quinoid ring.
In vitro formation of quinoid metabolites of the dietary supplement Cimicifuga racemosa (black cohosh).
1]) Functional groups PANI POA Benzoid and quinoid rings 1585 1586 C=C aromatic 1460 1460 Aromatic amine 1377 1377 C-O aromatic - 1257 C-O-C ether - 1118 C-N-C 1165 1123 C-H out of plane 829 850
Their quinoid transition states are shown as intermediate species for proton transfer but on [sup.
The electrochemical oxidation of the bis-aniline units to the quinoid state released protons to the electrolyte solution, while the reduction of the quinoid bridges resulted in the uptake of protons from the electrolyte.
Toxicity of hydroxylated and quinoid PCB metabolites: inhibition of gap junctional intercellular communication and activation of aryl hydrocarbon and estrogen receptors in hepatic and mammary cells.
1] is for the quinoid rings, while the lower frequency mode at 1500 [cm.
obliqua were investigated, either in terms of their biological activity or their phytochemical makeup, although one may assume that since quinoid compounds are such a notable constituent for other species in the genus (Hegnauer, 2001), they probably occur in S.
transition and the band in the visible region corresponds to the inter-ring charge transfer associated with excitation from benzenoid to quinoid moieties.
3] anion of CSA and the quinoid imine coexists in the PAni doped with CSA [14].