Anthracene, reactivity

Dyes, Dye Intermediates, and Naphthalene. Several thousand different synthetic dyes are known, having a total worldwide consumption of 298 million kg/yr (see Dyes AND dye intermediates). Many dyes contain some form of sulfonate as —SO H, —SO Na, or —SO2NH2. Acid dyes, solvent dyes, basic dyes, disperse dyes, fiber-reactive dyes, and vat dyes can have one or more sulfonic acid groups incorporated into their molecular stmcture. The raw materials used for the manufacture of dyes are mainly aromatic hydrocarbons (67—74) and include ben2ene, toluene, naphthalene, anthracene, pyrene, phenol (qv), pyridine, and carba2ole. Anthraquinone sulfonic acid is an important dye intermediate and is prepared by sulfonation of anthraquinone using sulfur trioxide and sulfuric acid. 

The polycyclic aromatic hydrocarbons such as naphthalene, anthracene, and phenan-threne undergo electrophilic aromatic substitution and are generally more reactive than benzene. One reason is that the activation energy for formation of the c-complex is lower than for benzene because more of the initial resonance stabilization is retained in intermediates that have a fused benzene ring. 

Bis(trifluoromethyl)-l,l-dicyanoethylene is a very reactive dienophile. It undergoes facile and high-yield [2+4] cycloadditions with 1,3-dienes, cyclopen-tadiene, and anthracene [707] (equation 86). It is reactive enough in a Diels-Alder reaction with styrene [702] (equation 86). 

In the presence of certain ethers such as Me20, Me0CH2CH20Me or tetrahydrofuran, Na forms deep-green highly reactive paramagnetic adducts with polynuclear aromatic hydrocarbons such as naphthalene, phenanthrene, anthracene, etc. ... 

It is notable that pyridine is activated relative to benzene and quinoline is activated relative to naphthalene, but that the reactivities of anthracene, acridine, and phenazine decrease in that order. A small activation of pyridine and quinoline is reasonable on the basis of quantum-mechanical predictions of atom localization encrgies, " whereas the unexpected decrease in reactivity from anthracene to phenazine can be best interpreted on the basis of a model for the transition state of methylation suggested by Szwarc and Binks." The coulombic repulsion between the ir-electrons of the aromatic nucleus and the p-electron of the radical should be smaller if the radical approaches the aromatic system along the nodal plane rather than perpendicular to it. This approach to a nitrogen center would be very unfavorable, however, since the lone pair of electrons of the nitrogen lies in the nodal plane and since the methyl radical is... 

The chloromethylation can be generally employed in aromatic chemistry benzene, naphthaline, anthracene, phenanthrene, biphenyls and many derivatives thereof are appropriate substrates. The benzylic chlorides thus obtained can be further transformed, for example to aromatic aldehydes. Ketones like benzophe-none are not reactive enough. In contrast phenols are so reactive that polymeric products are obtained. ... 

Because of their strong aromatic character, benzene and naphthalene are very unreactive as dienes however anthracene 19 reacts with highly reactive dienophiles, such as dehydrobenzene (benzyne) 20 ... 

Os04 will add to C=C bonds but will only attack the most reactive aromatic bonds thus benzene is inert, but it will attack the 9,10 bond in phenanthrene and will convert anthracene to 1,2,3,4-tetrahydroxytetra-hydroanthracene. It can be used catalytically in the presence of oxidizing agents such as NaC103 or H2O2 [53],... 

A small isotope effect has been observed in nitration of benzene by nitronium borofluoride in tetramethylene sulphone at 30 °C (kH/kD = 0.86) and this has been attributed to a secondary effect of the change in hybridisation from sp2 to sp3 of the ring carbon during the course of the reaction109. However, naphthalene gives an isotope effect of 1.15 under the same conditions, and anthracene a value of 2.6115. It does not seem at all clear why these relatively unhindered and normally more reactive molecules should give rise to an isotope effect when benzene does not. 

The first quantitative study of the reaction was carried out with anthracene-9-carboxylic acid (which possesses the necessary steric requirement by virtue of the peri-hydrogen atoms, and is very reactive at the 9 position towards electrophilic substitution). Schenkel632 found that the decarboxylation rate was increased in the presence of acid, and the first-order rate coefficients (believed to be in sec-1) are given in Table 205. It was subsequently concluded that in the absence of acid,... 

With this hypothesis, the calculated stability of the 9,10 addition compound of anthracene provides an explanation of the ease of attack of the 9,10 positions for addition. A similar calculation for phenanthrene shows that for this molecule too the 9,10 positions should be most reactive. 

The discovery that Lewis acids can promote Diels-Alder reactions has become a powerful tool in synthetic organic chemistry. Yates and Eaton [4] first reported the remarkable acceleration of the reactions of anthracene with maleic anhydride, 1,4-benzoquinone and dimethyl fumarate catalyzed by aluminum chloride. The presence of the Lewis-acid catalyst allows the cycloadditions to be carried out under mild conditions, reactions with low reactive dienes and dienophiles are made possible, and the stereoselectivity, regioselectivity and site selectivity of the cycloaddition reaction can be modified [5]. Consequently, increasing attention has been given to these catalysts in order to develop new regio- and stereoselective synthetic routes based on the Diels-Alder reaction. 

An example of a /zctcro-Diels-Alder reaction in SC-CO2 is the cycloaddition of anthracene with 4-phenyl-1,2,4-triazoline-3,5-dione, carried out at 40 °C and at a pressures between 75 and 216 bar [86]. The rate constant increases with decreasing pressure and the highest reactivity was observed at the critical pressure. The value of the rate constant at the critical pressure was higher than that observed in liquid CHCI3 and MeCN at the same temperature. At higher pressures, the rate is slower than that in the polar solvents, which reflects the apolar nature of SC-CO2 as a solvent. 

In fused ring systems, the positions are not equivalent and there is usually a preferred orientation even in the unsubstituted hydrocarbon. The preferred positions may often by predicted as for benzene rings. Thus it is possible to draw more canonical forms for the arenium ion when naphthalene is attacked at the a position than when it is attacked at the p position, and the a position is the preferred site of attack,though, as previously mentioned (p. 682), the isomer formed by substitution at the p position is thermodynamically more stable and is the product if the reaction is reversible and equilibrium is reached. Because of the more extensive delocalization of charges in the corresponding arenium ions, naphthalene is more reactive than benzene and substitution is faster at both positions. Similarly, anthracene, phenanthrene, and other fused polycyclic aromatic hydrocarbons are also substituted faster than benzene. 

This is consistent with the observed products of oxidation, i.e. benzyl alcohol, benzaldehyde and benzoic acid and with the observed oxidation of cyclohexane. Radical-cations are, however, probably formed in oxidation of napthalene and anthracene. The increase of oxidation rate with acetonitrile concentration was intepreted in terms of a more reactive complex between Co(III) and CH3CN. The production of substituted benzophenones at high CH3CN concentration indicates the participation of a second route of oxidation. 

In all of the cases in which dimerization has been observed, the yield of dimer formed, ranging from 40 to 70% under similar conditions, is less than that observed for anthracene. It should be recalled, however, from Chapter 1 that the yield is not a direct measure of the reactivity since it is dependent upon all other competing processes. 

For example, Beynon and Cwm coals when digested in anthracene oil give extraction yields of 68% and 47% respectively. This variation can be explained by reference to the maceral composition of the coals. Beynon coal contains a lower concentration of inertinite than the Cwm coal (Table V). In experiments where relatively pure samples of petrographic species were digested in anthracene oil, exinite and vitrinite were shown to be highly soluble, whilst in comparison the inertinite was almost completely insoluble. Similar variations in reactivity of macerals have been reported from studies of solubility in pure organic solvents (1(3). 

A system based upon the reactivity of coals during extraction with anthracene oil and phenanthrene has been developed. A convenient graphical method of expressing the data on Seyler s chart has been adopted. This method has limitations when dealing with prime coking coals, which show wide variations in extraction yield. The differences in extraction yield relate to the concentration of inertinite which is virtually insoluble in anthracene oil. 

A system of classifying coals for solvent extraction, based upon the extent of extraction when using anthracene oil and phenanthrene as solvents has been developed. The reactivity of the coals can be conveniently presented by superimposing the results on Seyler s coal chart. The effects of variations in maceral composition are also discussed. 

Solvent additives to the melt (Table 3) fall into two categories extractive and reactive. The extractive solvents (decane, perchloroethane, o-dichlorobenzene, and pyrrolidine) had negligible effect on solubility, possibly due to the preferential wetting of the coal by the solvent and exclusion of the ZnCl2 melt. Reactive solvents (anthracene oil, indoline, cyclohexanol, and tetralin) all incorporated strongly. Donor solvents, tetralin and indoline, increase the "corrected solubility, whereas anthracene oil and cyclohexanol have negligible effect. 

Another recent application to the activation of transition metals was reported (247) by Bonnemann, Bogdavovic, and co-workers, in which an extremely reactive Mg species was used to reduce metal salts in the presence of cyclopentadiene, 1,5-cyclo-octadiene, and other ligands to form their metal complexes. The reactive Mg species, characterized as Mg(THF)3 (anthracene), was produced from Mg powder in THF solutions containing a catalytic amount of anthracene by use of an ultrasonic cleaning bath. A plausible scheme for this reaction has been suggested ... 

Cyclopentadiene (6) reacted with 105 at 0°C to give 108 (entry 1). At 100°C, butadiene (12) afforded 109 (entry 2). No [2 + 2] cycloadduct was formed in either reaction. Perfluoromethylenecyclopropane (105) failed to react with cis,cis- or cis,trans-2,4-hexadiene at 100 °C, although 110 was readily formed from trans,frans-2,4-hexadiene (106) under these conditions [29] (entry 3). Anthracene (107) added to 105 at 100 °C. The dienophilicity of 105 is exceptional when compared with the reactivity of simple fluoroolefins, such as perfluoro-isobutylene, which require 150 and 200 °C to undergo cycloaddition to cyclopentadiene [30] and anthracene, respectively. 

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