Anthraquinone, hydrogenation

The above method has now been largely replaced by a newer process, in which the substance 2-ethylanthraquinone is reduced by hydrogen in presence of a catalyst to 2-ethylanthraquinol when this substance is oxidised by air, hydrogen peroxide is formed and the original anthraquinone is recovered ... 

Although considered an active participant in the process cycle, the tetrahydroaLkylanthraquinone (10) may not be a significant part of the catalytic hydrogenation because, dependent on the concentration in the working solution, these could all be converted to the hydroquinone by the labile shift per equation 17 and not be available to participate. None of the other first- or second-generation anthraquinone derivatives produce hydrogen peroxide, but most are susceptible to further reaction by oxidative or reductive mechanisms. 

The chemical yield of hydrogen peroxide and the anthraquinone per process cycle is very high, but other secondary reactions necessitate regeneration of the working solution and hydrogenation catalyst, and the removal of organic material from the extracted hydrogen peroxide. 

Working Solution Composition. The working solution in an anthraquinone process is composed of the anthraquinones, the by-products from the hydrogenation and oxidation steps, and solvents. The solvent fraction usually is a blend of polar and aromatic solvents which together provide the needed solubiUties and physical properties. Once the solution has been defined, its composition and physical properties must be maintained within prescribed limits for achieving optimum operation. 

Interest has continued in on-site manufacture of hydrogen peroxide from the elements, particularly for remote sites located considerable distances from wodd-scale anthraquinone processes. However, no commercial-scale direct combination plants have been constmcted as of this writing. 

High pressure Hquid chromatography (qv) (138) and coulometry can be used to detect and quantify anthraquinones and thek derivatives in a hydrogen peroxide process working solution. 

Diels-Alder Reaction. In 1928, Diels and Alder discovered that 1,3-unsaturated organic compounds reacted with quinoid systems to give partially hydrogenated, cycHc compounds. In the course of their work, they found that 1 mol of 1,4-naphthoquinone [130-15-4] reacted readily with 1 mol of 1,3-butadiene [106-99-0] to give a partially hydrogenated anthraquinone (11) l,4,4a,9a-tetrahydro-9,10-anthracenedione [56136-14-2] which, on oxidation with chromic oxide, produced anthraquinone (43) ... 

Indanthrones. Indanthrone blue (Cl Vat Blue 4) [81-77-6] (6) (Cl 69800) is the first invented anthraquinone vat dye, and has been extensively used as the most important vat dye for many decades because of its bright color as well as excellent affinity and fastness. These advantages are considered to be due to the stable stmcture attained by the intramolecular hydrogen bonding (145). 

Instead of using thermal energy to trigger the hydrogen abstraction mechanism, photo-induced reactions can be also be used to successfully crosslink acrylic PSAs [74-76], In this case, photoactive compounds, such as for example those containing benzophenone, anthraquinone or triazine nuclei are compounded with the polymer or copolymerized as one of the monomers. After drying, the adhesive... 

Lemus, R. H. Skibo, E. B. Design of pyritnido[4.5-s quinazoline-based anthraquinone mimics, structure-activity relationship for quinone methide formation and the influence of internal hydrogen bonds on quinone methide fate. J. Org. Chem. 1992, 57, 5649-5660. 

---