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Colour and Constitution
Author(s) -
HODGSON H. H.
Publication year - 1948
Publication title -
journal of the society of dyers and colourists
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.297
H-Index - 49
eISSN - 1478-4408
pISSN - 0037-9859
DOI - 10.1111/j.1478-4408.1948.tb02508.x
Subject(s) - hypsochromic shift , bathochromic shift , chemistry , steric effects , intramolecular force , hyperconjugation , molecule , resonance (particle physics) , computational chemistry , stereochemistry , crystallography , organic chemistry , physics , quantum mechanics , fluorescence
The novel kind of intramolecular reaction assumed by Ufhtzev to explain the appearance of colour in colourless compounds of the type C 6 H 5 ·NH·CH 2 ·C 6 H 4 ·NO 2 or C 6 H 5 ·NH·CO·C 6 H 4 ·NO 2 when the phenyl is replaced by the acenaphthenyl or fluorenyl group is shown t o be unnecessary, since the ordinary classical theory will suffice if the Baker‐Nathan effect (hyperconjugation) be operative. Steric hindrance of resonance and consequent lack of coplanarity in molecules can explain absence or only partial development of substantivity of dyes and also hypsochromic effects, while the same hypothesis is shown to throw considerable doubt on the validity of the alleged structure of cis ‐azobensene, which is bathochromic compared with tram‐azobenzene, contrary to the reasonable view that the more strained structure, i.e. the cis , should be hypsochromic. The coplanar hypothesis is shown to provide an explanation of the substantivity of the dyes from the non‐coplanar 4:4′‐diamino‐o‐terphenyl. An explanation is also included for a previous over‐statement by the author for the substantivity of Naphtol AS‐G, and brief reference is given to the recent confirmation by absorption spectra of the ionic quinonoid structures assumed by the present author for the coloured diazophenols and diazonaphthols.