Color Rule Research Articles

Energie und Ladungsverteilung von elektronisch angeregten Zuständen mehrfach substituierter Benzole: Eine quantenchemische Deutung der WITT‐DILTHEY‐WIZINGER'schen Farbregeln

AbstractThe MO method «molecules in molecules» due to Longuet‐Higgins and Murrell has been applied to models of di‐, tri‐ and tetra‐substituted benzenes carrying electron donating and electron accepting substituents in various relationships. It is shown that their general behaviour is in semi‐quantitative agreement with the observed spectroscopic properties of corresponding molecules (colour rules).

The Colour of Organic Compounds IV—Indigo and Related Dyes*

It is shown that the application to the indigo molecule of known colour rules, particularly the general rule given by the author1, leads to the expectation of a deep colour. Various isomers, analogues, and derivatives of indigo and thioindigo are similarly examined, and their colour is explained on a qualitative basis.

Absorption Spectra of Some 2,4-Dinitrophenylhydrazones

It has been pointed out by Redemann that the crystalline 2,4-dinitrophenylhydrazones of α,β-unsaturated carbonyl compounds are usually bright red in contrast to the yellow colors of the corresponding saturated derivatives. In view of the widespread interest in the use of 2,4-dinitrophenylhydrazones as derivatives for the identification and characterization of carbonyl compounds, coupled with the fact that a number of exceptions are known to the above-mentioned color rule, we have undertaken a study of the absorption spectra of a number of dinitrophenylhydrazones in neutral and alkaline solutions to see if more reliable criteria for the structure and degree of unsaturation of the original compounds could be obtained.