New insight on the mechanism of the catalytic hydrogenation of nitrobenzene to 4-aminophenol in CH3CN–H2O–CF3COOH as a reusable solvent system. Hydrogenation of nitrobenzene catalyzed by precious metals supported on carbon

Abstract

a b s t r a c tThe preparation of 4-aminophenol via hydrogenation of nitrobenzene in a single liquid phase has been carried in the presence of different precious metal catalysts. The liquid phase is composed of CH 3 CN-H 2 O-CF 3 COOH, which can be easily distilled at low temperature, thus avoiding work-up operation. The yield of 4-aminophenol is in the range 45% and in the presence of sulfolane as promoter reaches almost 50%. The best result has been obtained in the presence of Pt/C as hydrogenation catalyst. The role of the solvent is strictly related to the selectivity to 4-aminophenol, since CH 3 CN decreases the hydrogenation activity compared to other solvent, CF 3 COOH promotes the formation of the desired product both via Bamberger rearrangement in solution as well by a surface catalyzed reaction, while H 2 O is responsible for 4-aminophenol formation in both reactions. Even though, nitrosobenzene and phenylhydroxylamine have not been observed, their reactivity suggest a complex pattern of reactions occurring either on the catalyst surface or in the solution. Indeed, formation of 4-aminophenol may occur both in solution, via acid catalyzed Bamberger rearrangement and on the catalyst surface by the formation of a surface Pt-nitrenium complex, which undergoes surface nucleophilic attack by H 2 O.

Experimental Investigation of a Novel Formulation of a Cyanoacrylate-Based Adhesive for Self-Healing Concrete Technologies

“…Styrene is widely recognized as a mutagen and thus potentially carcinogenic (Quartarone et al, 2014), as such its inclusion in the formulations is not recommended, although it will be included here for completeness. Due to concerns regarding the interaction of acetic acid with the highly alkaline nature of the hydration reactions of the cementitious matrix, the only remaining candidate solvent is the acrylic acid.…”

Trifluoroacetic Acid Hydroxylamine System as Organocatalyst Reagent in a One-Pot Salt Free Process for the Synthesis of Caprolactam and Amides of Industrial Interest

“…Recently, the chemistry of trifluoroacetic acid as organocatalyst has been suggested for the synthesis of the caprolactam, of other amides as well as to several other reactions of industrial interest [7][8][9][10][11][12][13][14][15][16]. For instance, some authors proposed the direct oximation and rearrangement of ketones and in particular, of the cyclohexanone, to the corresponding amides [15][16][17][18][19][20]. The second important process in term of amide produced is the Hoechst-Celanese process for the synthesis of the N-acetyl-4-aminophenol (acetaminophen).…”

“…A simplification of the process can be attained by carrying out these two latter stages in one-pot [23]. During the last decade our research group, Luo and coworkers have published independently some papers where oximation and Beckmann rearrangement occur in one pot in high yield [15][16][17][18][19]23]. The kernel of the process is using a mixture of trifluoroacetic acid and acetonitrile, which allows high yield in the amides [15][16][17][18]23].…”

The use of M@p(4‐VP) and M@p (VI) (M:Co, Ni, Cu) cryogel catalysts as reactor in a glass column in the reduction of p‐nitrophenol to p‐aminophenol under gravity

“…Lately, the reduction of p‐NP to p‐AP via common metal nanoparticle catalysts in the presence of NaBH 4 has attracted quite attention in elimination of p‐NP . Additionally, the hydrogenation mechanism in the presence of heterogeneous catalysts were also deeply investigated . Reduction of p‐NP, a “model catalytic reaction” with sodium borohydride (NaBH4), takes place in the presence of a catalyst, which under mild chemical conditions produces a single product called p‐AP .…”