New Evidence for the Key Role of Hydrogen Bonding Between N‐Hydroxyphthalimide and Halide Ionic Liquids in Hydrocarbons Oxidation

Abstract

This paper demonstrates the catalytic activity of ionic liquids with an 1‐alkyl‐3‐methylimidazolium cation ([Rmim][X]) in the oxidation of ethylbenzene as a model hydrocarbon. The interaction between ionic liquids and N‐hydroxyphthalimide (NHPI) were examinated with or without Co(II). The activity of the studied ionic liquids and selected tetraalkylammonium salts ([R4N][X]) is compared. The influence of the structure of the alkyl substituents [R] and anions (in which [X]=[Cl], [Br], or [I]) on the reaction course was determined. The interaction between NHPI and the selected ionic liquids was proven using 1H NMR. It was shown that the formation of hydrogen bonds between the hydrogen atom in the −NOH group in NHPI and the anion [X] in [Rmim][X] influenced the rate of the oxidation reaction by accelerating the formation of the N‐oxyl radical responsible for the NHPI activity.

Photo- and Solvent-Mediated Production of the Highly Reactive N-Oxyl Radical and Its Efficient Catalytic Oxidation of Hydrocarbons at Ambient Temperature

“…When the solvent was adjusted to HFIP, excellent catalytic activity was obtained, and the conversion of EB reached 91.4% (entry 5, Table ). When the reaction time was extended to 8 h, the conversion of EB could further increase to 98.0% (entry 6, Table ), which is much higher than the reported data in refs –,,, and . With CH 3 CN as the solvent and being operated at 40 °C for 10 h under the photoirradiation of 18 W blue LED light (455 nm), 74% conversion of EB was obtained with NHPI/α-Fe 2 O 3 as the catalyst .…”

“…With CH 3 CN as the solvent and being operated at ∼35 °C for 12 h under the photoirradiation of a 350 W Xe lamp (450 nm), 74.1% conversion of EB was obtained with NHPI/FeO x /ZSM-5 as the catalyst . In addition, compared with the thermal catalysts such as ZIF-67/NHPI, NHPI/Co­(acac) 2 /[C 10 mim]­[Cl], and NHPI/Cu 3 (PO 4 ) 2 , with which about 32.6–94.5% conversions were obtained in 6–12 h, the present results also showed predominance. Nearly 100% conversion was first obtained at ambient temperature in a shorter time.…”

Coupled Interface and Oxygen-Defect Engineering in Co3O4/CoMoO4 Heterostructures toward Active Oxidation of Ethylbenzene

“…The aerobic oxidation of ethylbenzene (EB) is an appealing way for the production of acetophenone (AcPO), which has found myriad applications in the manufacturing of pharmaceuticals, plasticizers, perfumes, and other fine chemicals. 20,21 Although some good reaction results have been reported, various solvents and/or additives are required in these studies. 22−25 The aerobic oxidation of EB under solvent-and additive-free conditions has recently attracted great attention, which is desirable but still highly challenging.…”

“…The aerobic oxidation of ethylbenzene (EB) is an appealing way for the production of acetophenone (AcPO), which has found myriad applications in the manufacturing of pharmaceuticals, plasticizers, perfumes, and other fine chemicals. , Although some good reaction results have been reported, various solvents and/or additives are required in these studies. − The aerobic oxidation of EB under solvent- and additive-free conditions has recently attracted great attention, which is desirable but still highly challenging. Despite the limited attempts in this domain, the reported catalysts unfortunately suffered from several disadvantages including sluggish kinetics, unsatisfactory selectivity, poor stability, and complex and multiple preparation steps. − Hence, the exploration of a catalyst with preferable catalytic activity, attractive product selectivity, robust stability, and a low-cost and facile synthesis procedure is still ongoing and is the key to improving this oxidation strategy.…”

Redox-active and Brønsted basic dual sites for photocatalytic activation of benzylic C–H bonds based on pyridinium derivatives

“…[1][2][3][4] C-H bonds are thermodynamically strong and dynamically inert; sacrificial and expensive terminal oxidants, additives and/or harsh reaction conditions are commonly needed in traditional oxidation including thermal catalysis. [5][6][7][8][9][10] As an atom economical and environmentally benign alternative, photocatalysis can produce more active intermediates via energy or electron transfer from the excited state, and thus may provide a mild approach to the reactions that are difficult to achieve with thermal energy. Significant efforts have been devoted to exploring effective ways of photocatalytic oxidation of the C-H bond, in particular with the use of molecular oxygen as the green and sustainable oxidant.…”