Photochemistry and radiation chemistry of anthraquinone-2-sodium-sulphonate in aqueous solution. Part 1.—Photochemical kinetics in aerobic solution

Abstract

When aqueous solutions of anthraquinone-2-sodium-sulphonate (D) are photolyzed the quinone becomes hydroxylated and (in the absence of oxygen) redud. On the basis of the kinetics of the photohydroxylation in air or oxygen saturated solutions (PH 2-14), two alternative mechanism are proposed, the 3D*/S (S = H 2 0 or OH-) and the 3D*/D. In the former, D attacks S to produce an adduct DOHwhich is converted by ground-state D to the radical DOH-. In the latter, 3D* attacks D to form a solvent caged radical pair (Do+ De-), the Do+ constituent then reacting with S to give OH. radicals which with D yield DOH-. This intermediate is converted by oxygen to hydroxy product. Neither continuous irradiation kinetics nor conventional p flash photolysis permits discrimination between these schemes. The thermodynamic feasibility of OH. production by the 3D*/D reaction is demonstrated.

Photoreduction of 9,10-Anthraquinone Derivatives: Transient Spectroscopy and Effects of Alcohols and Amines on Reactivity in Solution¶

“…The semiquinone radical is scavenged by oxygen. The photoconversion of AQ is suggested to yield QH 2 in all the cases examined (Tables 4 and 5), in full agreement with the reports in the literature for parent AQ (9–12,20,21). In contrast to the 9,10‐derivative, a cyclohexyl adduct with Φ d = 0.1 is formed for the 1,4‐derivative in cyclohexane, whereas the major product of 1,4‐anthraquinone in carbon tetrachloride is a photodimer (45).…”

“…The photochemistry of 1,4‐benzoquinone and derivatives have been investigated intensively over the years (2–8). Most frequently, the photoprocesses of 9,10‐anthraquinone (AQ, Q in the schemes) (8–19) and the 1‐ and 2‐sulfonated or 1,5‐ and 2,6‐disulfonated derivatives, AQS1, AQS2, AQS3 and AQS4, respectively, have been studied by various methods (20–32). Photoinduced electron transfer from a suitable donor to the triplet state of AQ involves the semiquinone radical · QH/Q ·− , and the main photoproduct is 9,10‐dihydroxyanthracene (hydroquinone: QH 2 ).…”

“…A complication arises because QH 2 , in contrast to other hydroquinones, is not stable in solution, and addition of oxygen to QH 2 causes a complete recovery into AQ (10,20). The triplet state behavior of sulfonated AQ in water is rather complex and may be influenced by π,π* and n,π* triplet levels (21–27). The triplet properties of AQ and the conditions of photoreduction still lack clarity.…”

Phototransformation of 4-phenoxyphenol sensitised by 4-carboxybenzophenone: Evidence of new photochemical pathways in the bulk aqueous phase and on the surface of aerosol deliquescent particles

“…Such a process would also involve reduction of CBP. Usually, the reduced radical species arising from such processes (formed by addition of an electron or a H atom) are recycled back to the starting compound (CBP in the present case) by reaction with molecular oxygen (Clark and Stonehill, 1972). In this scenario the presence of a substrate such as 4PP should inhibit the transformation of the sensitiser, by channelling tripletsensitizer reactions toward the regeneration of the starting compound (Maurino et al, 2008).…”

The radiation chemistry of aqueous solutions of sodium 9,10-anthraquinone-2-sulfonate

“…The most obvious explanation for these phenomena would be a base-induced change in the nature of the radical species involved. Clark and Stonehill (1,15) have proposed that the hydroxyl radical adducts undergo acid dissociation of the hydroxyl group and isomerization in the p H range 9-1 1. However, Hulnle el (11. reported there was no change in the absorption spectrum of the hydroxyl radical adduct in the p H range 3-12.…”