Intermolecular Photochemical Reduction of Aromatic Nitro-compounds

Frolov, A. N.; Kuznetsova, N. A.; El'tsov, A. V.

doi:10.1070/rc1976v045n11abeh002755

Cited by 21 publications

(9 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Below pH 3 they suffer acid-catalyzed hydrolysis, to give m-nitrobenzaldehyde, the corresponding alcohol fragment, and hydrogen peroxide (eq. [4]). Hydrogen peroxide was detected after complete hydrolysis, by its characteristic reaction with KI (to give 12).…”

Section: Product Studiesmentioning

confidence: 99%

“…[4] slow and an overall dehydration pathway takes over, which gives the corresponding esters 14-16 as the product. Pseudo first-order rate constants of acid-catalyzed hydrolysis were measured as a function of pH for 11-13 via uv spectrophotometry, by monitoring for the formation of m-nitrobenzaldehyde.…”

mentioning

confidence: 99%

“…Trace 1 was taken immediately after photolysis at 254 nm (Rayonet reactor). Traces [2][3][4][5][6][7][8][9] were recorded initially about every 10 min after the addition of several drops of 30% &So4 to the cuvette solution, later increasing to every 20 min. a,&-Dideutero-m-and p-nitrobenzyl alcohols (a,a-d-1 and a,a-d-7, respectively) were readily available from a previous study (6,7).…”

mentioning

confidence: 99%

See 2 more Smart Citations

Photooxygenation of nitrobenzyl derivatives. Mechanisms of photogeneration and hydrolysis of α-hydroperoxy nitrobenzyl ethers

Wan¹,

Muralidharan²,

McAuley³

et al. 1987

Can. J. Chem.

View full text Add to dashboard Cite

Can. J. Chem. 65, 1775 (1987. ' The photooxygenation of nitrobenzyl derivatives 1-10 has been studied in aqueous solution as a function of pH. For m-nitrobenzyl ethers 2-4 and 9, stable a-hydroperoxy ethers (11)(12)(13) are the primary photochemical products. Acid hydrolysis of 11-13 gives m-nitrobenzaldehyde and hydrogen peroxide. Quantum yields for photooxygenation are reported for a number of derivatives as a function of pH. Acid and base catalyses of photooxygenation are observed for several compounds. A mechanism involving photogenerated nitrobenzyl carbanion intermediates is proposed.PETER WAN, S . MURALIDHARAN, IAIN MCAULEY et CHRISTOPHER A. BABBAGE. Can. J. Chem. 65, 1775 (1987. Operant en solutions aqueuses, on a CtudiC la photo-oxydation des dCrivCs nitrobenzyliques (1-10) en fonction du pH. Dans les cas des Cthers m-nitrobenzyliques (2-4 et 9), les produits photochimiques primaires sont les Cthers a-hydroperoxylCs stables (11-13). L'hydrolyse acide des composCs 11-13 conduit au m-nitrobenzaldkhyde et au peroxyde d'hydroghe. Dans les cas d'un certain nombre de derives, on rapporte les rendements quantiques pour la photo-oxygenation en fonction du pH.Dans les cas de plusieurs composCs, on a observe que la photo-oxygenation est soumise i une catalyse acidelbase. On propose un mCcanisme impliquant, comme intermkdiaires, des carbanions nitrobenzyliques gCnCrCs photochimiquement.[Traduit par la revue]The photochemistry of aliphatic and aromatic nitro compounds has received considerable attention and several reviews (1-4) have been published. Recently, we (5-7) and others (8, 9) have noted that some m-and p-nitro-substituted benzenes display unexpected reactivity when irradiated in aqueous solution, especially in the presence of hydronium and hydroxide ions as catalysts for the transformations (5-8). Whereas it is well known (1-4) that o-nitrobenzyl systems are photolabile due to the proximity to the substituent of the reacting nitro chromophore, resulting in initial intramolecular hydrogen abstraction via the n, T" triplet excited state, it had been assumed for many years that the corresponding meta and para derivatives should not be photolabile, except for simple photoreduction. However, in aqueous solution, a number of m-and p-nitro-substituted derivatives have been found to react via new photochemical processes (5-9). In a preliminary report (10) we had demonstrated that molecular oxygen can react with photoexcited nitrobenzyl derivatives, which represent an additional example of the rich and sometimes unpredictable photochemistry of m-and p-substituted nitroaromatic compounds. In this work, we report the generality and proposed mechanisms for the photooxygenation reaction of a variety of m-and p-nitro-substituted derivatives. In addition, the thermal aqueous chemistry of several photogenerated a-hydroperoxy m-nitrobenzyl ethers isolated in these studies will be presented. Results Product studiesThe compounds chosen for the study, 1-10, are shown below. Both m-and p-nitrobenzyl alcohols 1 and 7, respec...

show abstract

Section: Product Studiesmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Photooxygenation of nitrobenzyl derivatives. Mechanisms of photogeneration and hydrolysis of α-hydroperoxy nitrobenzyl ethers

Wan¹,

Muralidharan²,

McAuley³

et al. 1987

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…The photochemistry of nitroaromatic compounds has been a topic of continued interest and several reviews (1)(2)(3)(4) summarize the photochemical behaviour of this functional group in solution. Many photoreactions of nitro compounds are known to proceed via radical intermediates which in many examples (e.g., photoreduction) are formed via initial hydrogen transfer to the photoexcited nitro group, consistent with the notion of an electrophilic n, T * reactive state of the nitro group (5).…”

mentioning

confidence: 99%

“…In a typical experiment, 100 mg of the substrate is dissolved in aqueous CH3CN (100 mL; 10-30% CH3CN; pH [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and saturated with oxygen-free argon. Photolyses were carried out using quartz vessels in a Rayonet photochemical reactor (300 nm lamps).…”

mentioning

confidence: 99%

Photochemical retro-aldol type reactions of nitrobenzyl derivatives. Mechanistic variations in the elimination of nitrobenzyl carbanions from nitrobenzyl derivatives on photolysis

Wan¹,

Muralidharan²

1986

Can. J. Chem.

View full text Add to dashboard Cite

PETER WAN and S . MURALIDHARAN. Can. J. Chem. 64, 1949Chem. 64, (1986. The photochemical retro-aldol type reactions of several nitrobenzyl derivatives are reported. The reactions are observed only in aqueous solution with quantum efficiencies being pH dependent for several derivatives, consistent with the existence of several mechanistic pathways for reaction. The primary photochemical event is believed to involve the generation of a nitrobenzyl carbanion, which acts as a photolabile leaving group in these reactions, and the generation of an oxocarbocation (or oxocarbocation-derived) fragment.PETER WAN et S . MURALIDHARAN. Can. J . Chem. 64, 1949Chem. 64, (1986. On a CtudiC les rCactions photochimiques de type rCtro-aldol de plusieurs dCrivCs nitrobenzyles. On n'a observC ces rCactions qu'en solution aqueuse et les rendements quantiques dkpendent souvent du pH. Ceci tCmoigne de l'existence de divers chemins rkactionnels. On pense que la premi5re rCaction photochimique implique la formation d'un carbanion nitrobenzyle, agissant comme groupe photolabile ainsi que celle d'un fragment oxocarbocation (ou d'un dCrivC d'oxocarbocation).[Traduit par la revue]The photochemistry of nitroaromatic compounds has been a topic of continued interest and several reviews (1-4) summarize the photochemical behaviour of this functional group in solution. Many photoreactions of nitro compounds are known to proceed via radical intermediates which in many examples (e.g., photoreduction) are formed via initial hydrogen transfer to the photoexcited nitro group, consistent with the notion of an electrophilic n, T * reactive state of the nitro group (5). In this work, we report several closely related photochemical reactions of appropriately substituted nitroaromatic compounds which are observed only in aqueous solution and are best explained by proposing the formation of nitrobenzyl carbanion and oxocarbocation (or oxocarbocation-derived) intermediates, via an excited state configuration other than the usual n , r * . One of these reactions appears suited for direct photogeneration of a variety of dioxocarbocations and hemi-orthoesters in aqueous solution, which is amenable for flash-photolysis study. These results provide new insights into the intriguing photobehaviour of nitroaromatic compounds in aqueous solution (6-9).

show abstract