quinoidadj.n.

1894 G. M'Gowan tr. A. Bernthsen Text-bk. Org. Chem. (ed. 2) xxix. 490 In the dyes there is therefore present a peculiar nitrogen-carbon linking..which is reminiscent of the older quinone formula (‘quinoid linking’).

1938 G. H. Richter Textbk. Org. Chem. xxx. 627 The ortho and para quinoid structures show strong chromophoric properties.

1949 English & Cassidy Princ. Org. Chem. xx. 396 It is thought that some metabolic processes involve a reduction-oxidation system involving quinoid and hydroquinoid molecules.

1992 Chem. in Brit. (BNC) 28 150 The interatomic distances show that both quinoid and zwitterionic canonical forms contribute to the overall structure.

1907 Chem. Abstr. 1 300 (heading) Oxidation of benzidine. (VIII Communication on quinoids.)

1975 Lewis & Peters Facts & Theories Aromaticity v. 76 The quinones and quinoids generally are usually thought to be non-aromatic yet they apparently contain the magic 6π-electrons in a ring,..often regarded as characteristic of aromaticity.

1993 New Scientist 16 Jan. 16/1 Quinoids, such as quinic acid and benzoquinone, are important building blocks in the synthesis of many chemicals, from agrochemicals to pharmaceuticals.

1905 W. Autenrieth Detection of Poisons ii. 60 Very likely there is a shifting of the bond between oxygen and nitrogen which would give indophenol, the ‘quinoidal form’.

1994 Science 28 Jan. 513/3 The julolidinyl rings exhibit significant quinoidal character, as evidenced by the unequal C–C bond lengths in the rings.