Paradigms and paradoxes: Energetics of the oxidative cleavage of indigo and of other olefins

Abstract

Indigo is a unique organic compound in terms of its blue color and its multiple conjugated functional groups contained therein. We ask whether the enthalpy of its cleavage reaction into two isatin molecules reflects the novelty of either this color and/or the conjugated functionalities contained therein.Indigo, species 1, is quite unique among organic compounds. It has a unique "eponymic" blue color and extensive historic provenance and importance in numerous cultures in both the Western and Eastern hemispheres (cf. the derivation of the word "indigo" from "India"). Both of these aspects, the color and the importance, have shown fading-there are now other dyes of diverse and popular hues that fill the rainbow-rich human-derived landscape of fabrics and other materials. The blue color slowly fades in objects of art and commerce colored by indigo as the central C=C bond is cleaved by air and other ubiquitous oxidants.

A photochemical study on the blue dye indigo: from solution to ancient Andean textiles

“…In conclusion, even if, the major photodegradation product, isatin, is thermodynamically more stable than indigo, 33 we have confirmed that protected from light and in a dry environment, indigo is very stable. The central double bond may be the key for the extraordinary, and unexpected, stability of this organic molecule; it enables a very fast non-radiative deactivation process, from the excited to the fundamental state, locking the molecule and protecting it from photodegradation.…”

Interplay of thermochemistry and Structural Chemistry, the journal (volume 21, 2010) and the discipline

“…As such, the enthalpy of formation of thioindirubin is thus asked for, noting that the enthalpy of formation of indigo has been measured [248], albeit some 120 years ago. We note that the latter quantity was discussed in a recent study of the energetics of C=C bond cleavage for a variety of olefins [249] and so redetermination of this value is welcomed as well.…”

Paradigms and paradoxes: energetics of the oxidative cleavage of azo compounds (diazenes)

“…In this case, it is suggestive that O 2 should also be this state, even though that was not assumed in Ref. [1], and hence it will not be assumed here either.…”

“…Recently [1] we discussed the energetics of the oxidative cleavage of symmetric olefins, i.e. the enthalpy of the formal reaction…”