Anthrones

It is prepared by acidifying an alkali solution of anthrone or by reduction of anthraquinone with aluminium powder and concentrated sulphuric acid. 

Anthranol is isomeric with anthrone, and behaves in its reactions as a typical hydroxylic compound. The equilibrium mixture between the two compounds consists mainly of the keto form anthranol is largely converted into anthrone on heating. 

Reduction of anthraquinone gives dianthryl, anthrone and finally anthracene. 

It is a valuable dyestuffs intermediate. When fused with KOH, two molecules of benz-anthrone combine at the positions marked above to give a dibenzanthrone which is in itself a vat dye. Also used as an intermediate for the preparation of the valuable Caledon Jade Green. 

Reduction of anthraquinone with tin and concentrated hydrochloric acid in the presence of boiling glacial eicetic acid gives anthrone this substance (keto form) under certain conditions passes into the enol form, anthranol ... 

Anthrone [90-44-8] M 194.2, m 155 , pK -5.5 (aq H2SO4). Crystd from a 3 1 mixture of benzene/pet ether (b 60-80 ) (10-12mL/g), or successively from benzene then EtOH. Dried under vacuum. 

Dipping solution For ketoses Dissolve 300 mg anthrone in 10 ml acetic acid and add in order 20 ml ethanol, 3 ml 85% phosphoric acid and 1 ml water [1]. 

Spray solution For glycolipids Carefully add 72 ml cone, sulfuric acid to 28 ml water with cooling. Dissolve 50 mg anthrone in the mixture with gentle warming [5]. 

Carbonyl derivatives react with anthrone in acidic medium to yield condensation products of types 1 (pentoses) or 2 (hexoses) [9] ... 

FIGURE 2.7 SEC elution profiles of dextran in clinical samples, serum ( ) and urine ( ). The first peak represent dextran and the second peak inulin (used as a reference for clearance). The content of carbohydrates was determined in collected fractions with the anthrone method. [Reproduced from Hagel ef of. (1993), with permission.]... 

First, try to draw resonance contributors for both ground state and triplet anthrone. Then display a spin density surface for the triplet state of anthrone. (Note that the spin density surface shows the location of both unpaired electrons, one of which may be in a 7t orbital and one of which may be in a o orbital.) Where are the two unpaired electrons Are they localized or delocalized Given that spin delocalization generally leads to stabilization, would you expect the triplet state of anthrone to be stable ... 

Compare the geometries of triplet and ground state singlet anthrone. Where do they differ the most Focus on the carbonyl group. Has the CO bond distance altered Does the molecule incorporate a fully-developed CO n bond (as in ground state singlet anthrone), or a single bond (as in phenol) Is the carbonyl carbon planar or puckered Rationalize your observations. 

Spin density surface for triplet anthrone locates the two unpaired electrons. 

The liquid is filtered with suction through a Gooch crucible with a fixed porous plate (Note 1), and 100 cc. of water is added. The anthrone crystallizes at about io°. After being dried on a porous plate, it melts at about 153° (corr.). The yield is 80 g. (82.5 per cent of the theoretical amount). On rccrystal-lization from a 3 1 mixture (Note 2) of benzene and petroleum ether about 60 g. of anthrone melting at 154-155° (corr.) is obtained (62 per cent of the theoretical amount). 

The proportions do not make much difference as far as the yield is concerned, but the substance is more soluble in mixtures rich in benzene. About 10-12 cc. of the 3 1 mixture is required for each gram of anthrone. The anthrone may be more readily dissolved if it is added to the estimated quantity of hot benzene on the steam bath, and the petroleum ether is then added. About two-thirds of the mother liquor may be distilled off through a condenser and used in later runs. The residual mother liquor deposits about 12 g. of rather impure anthrone. 

Anthrone has been prepared by the reduction of anthra-quinonc with tin and hydrochloric acid,1 and with aluminium bronze.2... 

In a i-l. beaker equipped with a separatory funnel, a mechanical stirrer, and a thermometer, 20 g. (0.1 mole) of anthrone (p. 8) is dissolved in 300 cc. of glacial acetic acid. While the mixture is kept at 6o and stirred, a solution of 7 cc. of fuming nitric acid (sp. gr. 1.5) in 50 cc. of glacial acetic acid is rim in during one hour. 

Nitroanthrone has been prepared by the nitration of anthracene in isobutyl alcohol,1 and by the nitration of anthrone.2... 

Quinone diazides can also be obtained by the diazo group transfer reaction of 4-tosyl azide. For example, 9-diazo-10-anthrone (2.55) is formed from anthrone (2.54) if the reaction is carried out in an ethanol-piperidine mixture. On the other hand, if ethanol is replaced by pyridine, dimerization with loss of molecular nitrogen takes place and the azine 2.56 is isolated (Scheme 2-32 Regitz, 1964 Cauquis et al., 1965). In the preceding discussion tosyl azide was shown to be an electrophilic reagent. It therefore seems likely that it is not the anthrone 2.54 but its conjugate base which reacts with tosyl azide. 

Bei inverser Zugabe von Natriumboranat erhalt man aus Anthron 91% d.Th. 9,10-Dihydro-anthracen. 

---