Double Indigo

Double Indigo, the god of the liver, who is none other than Lord Lao himself, is invoked for the same purpose ... 

Flesh Child (Rouzi), Double Indigo (Lanlan) Be my friend, stay here and be my envoy I want to obtain the Divine Elixir of the Great One and ingest it Let me live a long life Do not leave my body Constantly reside within the Palace of the Purple Chamber, joined with the Dao (Laozi zhongjing, sec. 28)... 

It yields a characteristic reaction with bromine. If a few drops are, dissolved in 3 c.c. of glacial acetic acid and a little bromine vapour allowed to pass down the tube, a fine crimson colour forms which rapidly extends to the whole of the liquid and soon changes to violet and then to indigo blue with phosphoric acid, the acetic acid solution gives a rose madder colour at the junction of the liquids, and when the liquids are mixed, the colour changes to crimson and then slowly to violet. Baker and Smith consider that the sesquiterpene contains one double linkage. Semmler considers that it is a mixture of at least two bodies, one a bicyclic and the other a tricyclic sesquiterpene. 

The best known oxidative transformation of indigo is that into isatin. This is a normal oxidation at a double bond ... 

Chlorine is one of those allotropic bodies with a double form of existence—active and passive. As commonly prepared it is in its passive state but on exposure to the indigo rays, or other causes, it changes and assumes an aotive form. In this latter state, its affinity for hydrogen becomes so great that it decomposes water without difficulty. 

The concentration of aqueous ozone can be determined by the decolorization of indigo trisulfate (X = 600 nm). The method is stoichiometric and extremely fast. The indigo molecule contains only one C = C double bond which can be expected to react with ozone directly and with a very high reaction rate (see Figure 2-7). 

Indigo (24) can be pyrolysed in good yield, with double ring expansion, to form tetracycle (25) (Scheme 17) <95AG(34)67>. 

Ferric carbonyl ferrocyanide, Fe[Fe(CN)5CO], is prepared by double decomposition of an excess of ferric chloride solution and the potassium salt.1 It resembles indigo in appearance, and contains about 4 per cent, of combined water.2 Dried at a moderate temperature, it yields a friable resinous mass with a brilliant conchoidal fracture.1... 

However, there are also molecules in which the steric strain can be relieved only by twisting formal double bonds. In this case then, the destabilization of the ground state is larger than that of the excited state, where the double-bond character of the bond to be twisted usually is weaker. This effect, which can be used to explain the longer-wavelength absorption of N,N-dimethylindigo (44, = 670 nm) compared to indigo = 610... 

Only a very few 4,4 -bis(2-pyrazolin-5-ones) linked by a double bond have been prepared. The parent compound of this series, 4-(3-methyl -1 -phenyl - 5 - oxo - 2 - pyrazolin - 4-ylidene)-3-methyl-l-phenyl-2-pyrazolin-5-one (XXII-D), is known as pyrazole blue.323,807,809,816, 1090,1091 was so nameci by Knorr because of its great resemblance to indigo blue. All these compounds are strongly colored. The usual synthesis is by ferric chloride oxidation of monomeric 2-pyrazolin-5-ones (eq. 61)296,809 or by oxidation of the corresponding bis compounds... 

Figure 1.2.11 The color of indigo is caused by a double-crossed conjugation system of two NH electron donors and two CO electron acceptors. The benzene rings contribute very little.

The bicychc C14 aromatic hydrocarbon chamazulene with antiphlogistic properties is a characteristic compound present in German chamomile and some Achillea millefolium, agg chemot3tpes. Due to its system of conjugated double bonds, it confers a deep blue color to the essential oil. A blue azulene derivative is also present in the mushroom Lactarius indigo. 

---