Anthraquinone from phthalic anhydride

For syntheses of anthraquinone from phthalic anhydride compare Chap. IX. 6, p. 352. As a dye alizarin is very important. This is due to its power of forming very stable beautifully coloured internally complex diphenoxides with the hydroxides of plurivalent metals (Cu, Sn, Cr, Fe, Al). The best known is the bright red aluminium lake Turkey red . 

The direct synthesis of anthraquinone from phthalic anhydride and benzene has been reported to proceed over zeolite Beta [50] in a shape selective manner. In a conventional anthraquinone synthesis, anthracene is used as a feedstock for oxidation. Once there is a shortage of it in the market, additional anthracene could be produced by isomerization of its isomer, viz. phenanthrene. This, however, is not possible by direct isomerization of the trinuclear aromatic system but involves the partially (symmetrically) hydrogenated species. Consequently, isomerization of symmetrical octahydrophenanthrene to symmetrical octahydro-anthracene was studied by Song and Moffatt [51]. As sketched in Figure 3, a high yield of symmetrical octahydroanthracene can be obtained over zeolite H-mordenite (ngj/nyy = 8) at 250 °C (liquid phase, decalin as solvent). These examples show that (shape selective) catalysis on zeolites is more and more expanding into the conversion of polycyclic aromatics, and we foresee continued interest and success in this field of zeolite catalysis. 

The formation of anthraquinone from phthalic anhydride and benzene by the Friedel and Crafts synthesis is conducted in the presence of aluminum chloride.58 Ortho-benzoyl benzoic acid is first formed and then... 

In the conversion of anthracene into anthraquinone, the para bond between the two carbon atoms involved in the oxidation is broken, but no change takes place in the benzene rings present in the compound. The synthesis of anthraquinone from phthalic anhydride confirms this view of its structure. When the anhydride is heated with benzene in the presence of a dehydrating agent, such as aluminium chloride, one molecule of water is lost and anthraquinone is formed —... 

Friedel-Crafts acylation is related to Friedel-Crafts alkylation, with an acylium cation acting as the electrophile. However, in industrial aromatic chemistry, because of the high consumption of catalyst, this reaction is of much less importance than Friedel-Crafts alkylation. Nonetheless, it has been used, for example, in the manufacture of anthraquinone from phthalic anhydride and benzene. 

Nair, M. G. Dhananjeyan, M. R. Kron, M. A. Milev, Y. Process for preparation of anthraquinones from phthalic anhydrides and hydroxyphenols in the... 

Dichloro-2,2 -dimethyl-1,1 -dianthraquinonyl can be synthesized by Friedel-Crafts reaction from phthalic anhydride and 2,6-dichlorotoluene. Subsequent cyclization of the resulting substituted benzoylbenzoic acid 102 in sulfuric acid affords the corresponding anthraquinone derivative 103, which is dimerized by Ullmann reaction ... 

Since, as the equation shows, this substance is converted by-concentrated sulphuric acid with loss of water into anthraquinone, a very important route to a much-studied group is opened up. Thus /S-methylanthraquinone, which serves as an intermediate for valuable vat dyes, is prepared technically in this way from phthalic anhydride and toluene. 

Exercise 22-19 Anthraquinone can be synthesized from phthalic anhydride and benzene in two steps. The first step is catalyzed by AICI3, the second by fuming sulfuric acid. Write mechanisms for both reactions and suggest why fuming sulfuric is required in the second step but not in the first. 

Methyl anthraquinone has been obtained by the oxidation of /3-methyl anthracene by several investigators 1 and material of the same origin, obtained by the benzene-extraction of crude commercial anthraquinone,2 has been fully described. As regards the synthesis from phthalic anhydride and toluene, both the preparation and properties of />-toluyl-o-benzoic acid 3 and the complete synthesis 4 have been the subject of several papers. This acid has also been prepared from o-carbomethoxy benzoyl chloride and toluene.5 The phthalic anhydride synthesis of anthraquinone derivatives in general has received considerable attention. An account of this work, together with extensive references, is given by Barnett.6... 

The oriAo-benzoyl-benzoic acids readily yield anthraquinone and its derivatives (see p. 82). It may be noted that o-benzoyl-benzoic acid itself, with benzene and aluminium chloride, yields phthalophenone the same compound is made directly from phthalic anhydride by increasing the amount of the latter or by adding acetic anhydride. The same holds for p-toluoylbenzoic acid and ditoluoylphthalide. (Am. Soc., 43, 1965 J. C. S., 122, 539.) (For the use of carbomethoxylbenzoyl chlorides and of homophthalic anhydrides in these reactions, see Am. Soc., 43, 1950.)... 

The production of anthraquinone dyes generally proceeds from a few key products generated by electrophilic substitution of unsubstituted anthraquinone or by synthesis of the nucleus. The major methods employed to prepare anthraquinone derivatives substituted in the a-position are sulfonation and nitration. Preparation of b-substituted anthraquinones and of quinizarin (1,4-dihydroxyan-thraquinone) generally is accomplished by synthesis of the nucleus starting from phthalic anhydride and a benzene derivative. 

The condensation of toluene with phthalic anhydride takes place in the presence f aluminum chloride even at room temperature and is complete after about 12 to 15 hours of stirring. The ring closure can be effected with 5 per cent oleum (10 parts for 1 part of toluylbenzoic acid) by heating on a water bath for 2 hours. Usually, however, the preparation is done exactly as described for the preparation of anthra-quinone from phthalic anhydride and benzene. The yield of 2-methyl-anthraquinone, melting at 170-174°C., is about 85 to 88 per cent of the theoretical amount calculated on the phthalic anhydride. 

Figure 5-5. Typical chromatogram of a reaction mixture collected during the course of reaction of phthalic anhydride with benzene in the presence of AICI3, as catalyst. Peaks 1, benzene 2, anthraquinone 3, phthalic anhydride 4, maleic anhydride 5, unknown. Chromatographic conditions Column Spherisob silica, 250 x 4.6mm, 10pm mobile phase, -heptane-ethanol-chloroform-acetic acid (89 5 5 1, v/v/v/v) flow rate, 1 mL/ min detection, UV at 254 nm temperature, 27°C. (Reprinted from reference 29, with permission.)...

It is questionable, however, whether this process can be economically applied on a commercial scale at the present time in competition with cheap anthraquinone produced from phthalic anhydride. 

Anthraquinone (A/Q). This product is mainly used for dyes, the classical route being the oxidation of anthracene (Figure 2.11) or the Friedel-Crafts route from phthalic anhydride (Figure 2.12). Alternative routes from benzene and ethylene and from naphthalene and butadiene have been studied on economic grounds. 

An important improvement with regard to both substrate tolerance and enantioselectivity of the AD was the introduction of the anthraquinone-bridged ligands (DHQ)2AQN and (DHQD)2 AQN [2]. These ligands are easily accessible from phthalic anhydride and 1,4-difluoro benzene, and in many aspects their catalytic behavior reflects that of the standard bis-cinchona alkaloids described in Section 6D.1. 

Anthraquinone is widely use in the manufacture of a range of dyes. Two possible routes for manufacturing anthraquinone are (1) from the reaction of 1,4-naphthoquinone with butadiene and (2) reaction of benzene with phthalic anhydride. Describe mechanisms for both these reactions and identify likely reaction conditions and any other reagents required. Compare the atom economy of the two routes. Identify three factors for each route that may influence the commercial viability. 

Anthraquinone itself is traditionally available from the anthracene of coal tar by oxidation, often with chromic acid or nitric acid a more modern alternative method is that of air oxidation using vanadium(V) oxide as catalyst. Anthraquinone is also produced in the reaction of benzene with benzene-1,2-dicarboxylic anhydride (6.4 phthalic anhydride) using a Lewis acid catalyst, typically aluminium chloride. This Friedel-Crafts acylation gives o-benzoylbenzoic acid (6.5) which undergoes cyclodehydration when heated in concentrated sulphuric acid (Scheme 6.2). Phthalic anhydride is readily available from naphthalene or from 1,2-dimethylbenzene (o-xylene) by catalytic air oxidation. 

The aroylation of an aromatic system by reaction with phthalic anhydride under Friedel-Crafts conditions is described in Section 6.11.1, p. 1006. The cyclisation of the derived o-aroylbenzoic acid with polyphosphoric acid is a convenient route to substituted anthraquinones. The reaction is illustrated by the formation of 2-methylanthraquinone from o-(p-toluoyl)benzoic acid (Expt 6.132). 

Air, often in the presence of a catalyst. Examples of this method are the preparation of phthalic anhydride from naphthalene by air and vanadium oxide (Wohl s method, page 171), and the analogous oxidation of anthracene to anthraquinone. In the latter case, anthracene which is not entirely pure can be used. 

The development of a normal-phase HPLC method was warranted due to the presence of phthalic anhydride, which is unstable in water. Analysis in organo-aqueous solvent systems that are used in RPLC would lead to an on-column reaction forming the respective carboxylic acid degradation product. Figure 5-5 shows the chromatogram obtained for the separation of 9,10-anthraquinone from the reactants and impurities on a silica column. The method was successfully applied to monitor the reaction conversion and also to determine the stability of 9,10-anthraquinone at the specified storage conditions. 

Fischer from tetrahydroindcne [253). In a similar manner, we obtained ferrocene analogs of anthronc and anthraquinone from ferrocene and phthalic anhydride. 

This synthesis is of the same general character as that of anthracene from phenyl ortho to y ketone (p. 794). In effect it is the condensation, by the elimination of water, of phthalic anhydride and benzene with the formation of anthraquinone which we may represent as... 

The common carrier gases are air or nitrogen or steam. Condensate from a carrier usually is finely divided, snowlike in character, which is sometimes undesirable. Substances which are subhmed in the presence of a carrier gas include anthracene, anthraquinone, benzoic acid, phthalic anhydride, and the formerly mentioned sah-cylic acid. 

The hydrogen atom in the ortho position to the carbonyl group unites with the hydroxyl group of the carboxyl to effect the ring closure. The preparation of o-benzoylbenzoic acid from benzene and phthalic anhydride (Experiment 63) and the dehydration of this keto acid to anthraquinone considered in the present experiment illustrate the building up of polynuclear compounds from simpler benzene derivatives. 

Synthetic anthraquinone. The advent of cheap phthalic anhydride in a very pure form and the production of pure aluminum chloride 5T in large quantities at low cost have made it possible for American manufacturers to synthesize the anthraquinone necessary for the manufacture of dyes in competition with those from anthraquinone obtained by the oxidation of anthracene as practiced in England and Germany. Today, synthetic anthraquinone and anthraquinone derivatives furnishes a large outlet for phthalic anhydride. 

The o-benzoyl benzoic acid is prepared by mixing phthalic anhydride with an excess of benzene and adding to an amount of aluminum chloride equimolar to the anhydride used. This mixture is maintained at a temperature of 35° C. in a lead lined kettle, jacketed for steam heating, for about half an hour. The temperature is then slowly raised to the boiling point of benzene and maintained until hydrochloric arid is no longer evolved. Benzene is removed by distillation with steam, the o-benzoyl benzoic arid dried and converted to anthraquinone by treatment with 95 to 98 per cent sulfuric acid at a temperature of from 110° to 150° C. for three-quarters to one hour. The anthraquinone thus fomied is recovered from the concentrated sulfuric acid by careful dilution of the acid with water or treatment with steam to obtain large crystals to facilitate filtration, removal of acid, and washing. 

When mixtures of anthracene and phenanthrene, such as are obtained by removing carbazole from anthracene press cake by caustic fusion, arc oxidized, mixtures of phthalic anhydride and anthraquinone result. A separation of these valuable products is effected by washing out the acids with an alkali solution and recovering as sodium salts or as acids by addification subsequent to removal of anthraquinone by filtration. The products may be distilled or sublimed to separate from any unoxidized material that may be present. Maleic acid may also be present in the products to a small extent and is recovered with the phthalic anhydride from which it must be removed as an impurity.88... 

---