Alizarin Nitro

Nitroalizarin (l,2-dihydroxy-3-nitro-9,10-anthraquinone. Alizarin Orange) [568-93-4] M 285.2, m 244" (dec), pKEst(i) 4.6, pKEst(2) 9.6. Crystd from acetic acid. 

Nitro-1,2-dihydroxy- or 3-Nitra-alizarin, long orn-yel ndls (from benz) or yel pits (from glac acet ac, ale or chlf), mp 244°... 

Sometimes the amine can be dispensed with, and the corresponding nitro-body used alone. It is reduced by the hydrogen arising in the reaction. Of technical interest is the fact that /J-nitro-alizarin on heating with glycerol and sulphuric acid yields a blue dye—Alizarin Blue. (B., 16, 445 29, 708 A., 201, 333.)... 

The main body of the solution of the nitro compound is then neutralized with soda ash to the point giving a permanent red coloration, and heated to 60-65°C. The calculated amount of concentrated hydrosulfide solution is added slowly with stirring, and the mixture is held at 60-65° for 3 hours. Enough salt is then added to make the solution 10 per cent with respect to salt, and the solution is cooled with stirring. The precipitated dye is filtered off, washed with 15 per cent salt solution until the washings are colorless, pressed out, and dried at 90°. The yield of alizarin saphirol B is about 105 grams. 

Nitro, amino and sulphonic acid derivatives of alizarin are also dyes of various colors and are known as alizarin orange, alizarin maroon, alizarin red, etc. Also there is present in the madder root another dye compound known as puipurin which is 1-2-4-tri-hydroxy anthraqui-none. Isomeric tri-hydroxy anthraquinones are dyes also but it is interesting that in all of these poly-hydroxy anthraquinones which are dyes two of the hydroxyls are always in the 1-2 positions. 

Other processes have been proposed for the manufacture of alizarin, for instance by melting dichloranthraquinone or nitro-anthraquinone [16] with caustic potash, but these processes have never attained commercial importance. 

Only the /8-nitro-compound (of the constitution OH OH NO3) possesses technical interest. It may be obtained by treating alizarin, suspended in toluene or nitrobenzene, with nitrous acid, or by cautious nitration of alizarin dissolved in glacial acetic acid with nitric acid. 

From alizarin there can be prepared, further, by nitration, the a- or /J-nitro-alizarin, and from this, by reduction, the corresponding amido-alizarin. From (i-nitro- and amido-alizariu, by heating with glycerol and sulphuric acid, the important Alizarin Blue is obtained. Further, by the action of fuming sulphuric add on alizarin there is obtained a tetraoxyanthraquinone (Bordeaux), etc. 

Alizarine Blue. 5 Dihydroxynaphtho[2,2 /]quin-oiine-7,l2 dione 7.8-dihydroxy-5,6-phthaly[quinoline Alizarin Blue R C.I. 67410- C 7H9N04 mol wt 291-25. C 70,10%, H 3.12%, N 4.81%, O 21,97%. Prepn from 3-nitro-alizarin, glycerol, and coned sulfuric acid Auerbach, J. 

A study of the products which result from the nitration of ahzarin, shows that formula (I) is correct. In the two mononitro derivatives formed, the nitro group is in combination with the ring to which the hydroxyl groups are joined, since the two derivatives yield phthalic acid on oxidation. As a compound of the structure represented by formula (II) could not yield two such mononitro derivatives, the conclusion is drawn that the structure of alizarin is that indicated by formula (I). 

Br , I , phosphate, and sulfate as TBA salts (100 equivalents) from left to right and (b) color changes of 4-nitro-l,2-phenylenediamine 20, alizarin 21, and 2,2 -bis(3-hydroxy-l,4-naphthoquinone) 22 in CH2CI2 (1 x lO M) by treatment with 100 equivalents of anions in the form of their TBA salts. (Redrawn from Ref. 54. Wiley-VCH, 2001.)... 

Dihydroxy-3-nitro-9,10-anthracenedione Alizarin Orange C,4H7N0e 568-93-4 285.209 oran nd or pi (HOAc) 244 dec sub sl HjO s EtOH, bz, chi, suit, HOAc... 

Nitrophenols and nitro-acids, (yellow to orange) salicyl-aldehyde (yellow) derivatives of alizarin JV-bromosucdn-imide phthaleins. 

Except for artificial alizarin, made from coal tar anthracene, practically all the early synthetic dyes were derived from, coal tar benzene and toluene. From the mid-1870s, however, interest turned to amino and nitro derivatives of the more abundant coal tar hydrocarbon naphthalene. These endeavours were assisted by the large body of theoretical, synthetic and analytical knowledge about aromatic chemistry that had become available during the decade following the announcement of Kekule s benzene ring theory (1865). Roussin s azo dyes were naphthalene derivatives. 

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