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Oxygenated organic molecules (OOMs), generated from the oxidation of various biogenic volatile organics with diverse yields, are a great contributor to SOA formation. Terpinolene is an isomeride of limonene, with a high SOA yield. Herein, we investigated the elaborate oxidation mechanism of terpinolene by OH and NO.sub.3, elucidating the new formation mechanism of OOMs and their yield profiles based on the newly-built zero-dimensional chemical model under three typical atmospheric conditions. For terpinolene oxidation by OH, H shift imposes restrictions on continuous autoxidation, instead by the reactions with HO.sub.2 /NO/NO.sub.2 resulting in chain termination. For the reaction of terpinolene with NO.sub.3, the transfer of the radical center via bond breaking, triggering a new round of autoxidation, is newly found to be pivotal in the formation of organic nitrate (RONO.sub.2) OOMs with high yields. The effective saturation concentration (C.sup.â) of RONO.sub.2 OOMs is mostly lower than the OOMs formed by OH oxidation, more easily distributed into the particle phase. The estimated C.sup.â of the generated OOMs is distinctly varied among OOM isomers, which emphasizes the necessity of determining their molecular structures, peculiarly the number of rings. The comparative analysis of OH-initiated (daytime) and NO.sub.3 -driven (nocturnal) terpinolene oxidation mechanism, highlighted the formation of RONO.sub.2 OOMs, would be conducive to molecular structure identification of OOMs in atmospheric monitoring and atmospheric chemical model refinement.

Photothermocatalytic oxidation technology stands out as one of the most environmentally friendly and effective approaches for VOC degradation, and the catalyst plays a pivotal role in this process. In this study, carbon-doped Co.sub.3O.sub.4 nanocomposites (C-Co.sub.3O.sub.4) were synthesized via the sol-gel method and employed for the photothermal degradation of toluene. The results reveal that the calcination temperature profoundly influences the photothermal catalytic performance of the materials. C-Co.sub.3O.sub.4-250, obtained by calcination at 250 °C, exhibits the largest specific surface area, superior low-temperature reduction capability, and enhanced oxygen species activity, leading to its optimal catalytic performance in the photothermal oxidation of toluene. Under a light intensity of 400 mW/cm.sup.2, toluene conversion reaches 95%, and the CO.sub.2 yield attains 80% on C-Co.sub.3O.sub.4-250 during continuous flow reactions, much higher than that of 18% and 10% on pure Co.sub.3O.sub.4.

The formation of secondary sulfate in the atmosphere remains controversial, and it is an urgent need to seek a new method to quantify different sulfate formation pathways. Thus, SO.sub.2 and PM.sub.2.5 samples were collected from 4 to 22 December 2019 in the Nanjing region. Sulfur and oxygen isotopic compositions were synchronously measured to study the contribution of SO.sub.2 homogeneous and heterogeneous oxidation to sulfate. Meanwhile, the correlation of [delta].sup.18 O values between H.sub.2 O and sulfate from SO.sub.2 oxidation by H.sub.2 O.sub.2 and Fe.sup.3+ / O.sub.2 was simulatively investigated in the laboratory. Based on isotope mass equilibrium equations, the ratios of different SO.sub.2 oxidation pathways were quantified. The results showed that secondary sulfate constituted higher than 80 % of total sulfate in PM.sub.2.5 during the sampling period. Laboratory simulation experiments indicated that the [delta].sup.18 O value of sulfate was linearly dependent on the [delta].sup.18 O value of water, and the slopes of linear curves for SO.sub.2 oxidation by H.sub.2 O.sub.2 and Fe.sup.3+ / O.sub.2 were 0.43 and 0.65, respectively. The secondary sulfate in PM.sub.2.5 was mainly ascribed to SO.sub.2 homogeneous oxidation by OH radicals and heterogeneous oxidation by H.sub.2 O.sub.2 and Fe.sup.3+ / O.sub.2 . SO.sub.2 heterogeneous oxidation was generally dominant during sulfate formation, and SO.sub.2 oxidation by H.sub.2 O.sub.2 predominated in SO.sub.2 heterogeneous oxidation reactions, with an average ratio around 54.6 %. This study provided an insight into precisely evaluating sulfate formation by combining stable sulfur and oxygen isotopes.

The utilization of biomass-derived compounds to produce abundant renewable bio-based chemicals has attract intense interest. The catalyzed oxidation of 5-hydroxymethylfurfural (HMF) is an useful strategy to produce value-added compounds, such as 2, 5-diformylfuran (DFF) and 2,5-furandicarboxylic acid (FDCA). The Co-MnO.sub.2 was developed as an efficient catalyst in HMF conversion under mild conditions. Solvents were investigated and play a vital role on the products distribution. The formation of DFF is facilitated in the organic solvent and 2,5-furandicarboxylic acid (FDCA) is favored to generate in H.sub.2O. As a result, a 87% conversion of HMF with 87% selectivity of DFF was detected in isopropanol, while a 95% FDCA selectivity at 93% HMF conversion was measured in H.sub.2O. Besides, organic solvents were found to affect the HMF selective oxidation reaction and base additives effect on the promotion of C-H and O-H bones activation in HMF molecule was also discussed. This work provide a tunable oxidation process in the transformation of HMF.

In the past 50 years, cross-coupling reactions mediated by transition metals have changed the way in which complex organic molecules are synthesized. The predictable and chemoselective nature of these transformations has led to their widespread adoption across many areas of chemical research. However, the construction of a bond between two sp(3)-hybridized carbon atoms, a fundamental unit of organic chemistry, remains an important yet elusive objective for engineering cross-coupling reactions. In comparison to related procedures with sp(2)-hybridized species, the development of methods for sp(3)-sp(3) bond formation via transition metal catalysis has been hampered historically by deleterious side-reactions, such as β-hydride elimination with palladium catalysis or the reluctance of alkyl halides to undergo oxidative addition. To address this issue, nickel-catalysed cross-coupling processes can be used to form sp(3)-sp(3) bonds that utilize organometallic nucleophiles and alkyl electrophiles. In particular, the coupling of alkyl halides with pre-generated organozinc, Grignard and organoborane species has been used to furnish diverse molecular structures. However, the manipulations required to produce these activated structures is inefficient, leading to poor step- and atom-economies. Moreover, the operational difficulties associated with making and using these reactive coupling partners, and preserving them through a synthetic sequence, has hindered their widespread adoption. A generically useful sp(3)-sp(3) coupling technology that uses bench-stable, native organic functional groups, without the need for pre-functionalization or substrate derivatization, would therefore be valuable. Here we demonstrate that the synergistic merger of photoredox and nickel catalysis enables the direct formation of sp(3)-sp(3) bonds using only simple carboxylic acids and alkyl halides as the nucleophilic and electrophilic coupling partners, respectively. This metallaphotoredox protocol is suitable for many primary and secondary carboxylic acids. The merit of this coupling strategy is illustrated by the synthesis of the pharmaceutical tirofiban in four steps from commercially available starting materials.

Perylenetetracarboxylic dianhydride (PTCDA) derivatives have received significant attention as molecule photocatalysts. However, the poor recyclability of molecule-type photocatalysts hinders their widespread applications. Herein, immobilization of PTCDA on Al[sub.2]O[sub.3] was achieved by simply physical mixing, which not only dramatically improved their recyclability, but also surprisingly improved the reactivity. A mechanism study suggested that the photo-exited state (PTCDA*) of PTCDA could promote the oxidation of thioanisole to generate PTCDA[sup.•−], which sequentially reduces oxygen to furnish superoxide radicals to achieve the catalytic cycle. Herein, the immobilization support Al[sub.2]O[sub.3] was able to facilitate the strong adsorption of thioanisole, thereby boosting the photocatalytic activity. This work provides a new insight that the immobilization of organic molecular photocatalysts on those supports with proper adsorption sites could furnish highly efficient, stable, and recyclable molecular-based heterogeneous photocatalysts.

A practical metal-free and additive-free approach for the synthesis of 6/7/8-membered oxacyclic ketone-fused isoxazoles/isoxazolines tetracyclic or tricyclic structures is reported through C[sub.sp] [sup.3]–H bond radical nitrile oxidation and the intramolecular cycloaddition of alkenyl/alkynyl-substituted aryl methyl ketones. This convenient approach enables the simultaneous formation of isoxazole/isoxazoline and 6/7/8-membered oxacyclic ketones to form polycyclic architectures by using tert-butyl nitrite (TBN) as a non-metallic radical initiator and N–O fragment donor.

[This corrects the article DOI: 10.1371/journal.pone.0253240.].[This corrects the article DOI: 10.1371/journal.pone.0253240.].

Iron(II) and manganese(II) complexes with N4Py [N4Py—N,N-bis(2-pyridylmethyl)-N-(bis-2-pyridylmethyl)amine] have been found to activate O[sub.2] for the oxidation of α-pinene in acetonitrile. For example, for 1 M α-pinene, 0.5 mM [(N4Py)Fe[sup.II]][sup.2+], and dioxygen as an oxidant, 90 mM α-pinene epoxide, 48 mM verbenol, and 50 mM verbenone have been formed, which, taking into account the concentrations of the minor products (myrtenol and myrtenal), gives a turnover number approximately equal to 400. Based on the amounts of products formed, the conversion of α-pinene is approximately 20% and 18% for iron and manganese catalysts, respectively. Although the manganese catalyst is somewhat less effective than the iron catalyst, the selectivity of the products is similar for both catalysts. Replacement of dioxygen with air as the oxidant causes the reaction yield to be lower. The proposed mechanism assumes the formation of a metal(IV)-oxo complex [(N4Py)M[sup.IV]=O][sup.2+], M–Fe or Mn, during the simultaneous combination of a catalyst, O[sub.2], and substrate, and its subsequent reactions toward the observed products.

The isothermal and thermal cyclic oxidation behaviour of NiCoCrAlY coatings sprayed using high-velocity air fuel (HVAF) and high-velocity air (oxy) fuel (HVA(O)F) processes was compared at 1100 °C and 1120 °C on Ni-based superalloy substrates. The evolution of the NiAl () phase and thermally grown oxide (TGO) was systematically analysed as a function of time, up to 100 h. The TGO grew from 2 to 3 m (after 20 h) to nearly 25 m after 40 h and comprised a mixed oxide layer of [alpha]-Al.sub.2O.sub.3 and NiO after 40 h under isothermal oxidation. The Al content in the coating mid-zone remains unchanged at 8-10 wt%, however, the Al content in the -depleted zone underneath the TGO drops to < 2 wt%, leading to a fully [gamma] microstructure after 50 h of isothermal exposure. The -depleted layer thickness increases with exposure time from 5 m after 20 h to nearly 45 m after 40 h. The key difference between HVAF and HVA(O)F coatings could be seen in the development, after isothermal exposure, of porosity in the case of HVAF, while the HVA(O)F remained dense. Thermal cyclic exposure after 20 h between room temperature and 1100 °C led to coating delamination in the case of HVAF coating, whereas HVA(O)F coatings remained intact. The delamination is attributed to the formation of pores in the vicinity of the grits. Overall, there seems little difference in the oxidation properties of the coatings between the two processes under isothermal exposure, whereas HVA(O)F shows better structural integrity after thermal cycling. The results in this manuscript are the first to show the behaviour of HVAF-based coating response to high-temperature heat treatment and the analysis thereof to look at the novel aspect of interchangeability of using these coatings for various high-temperature oxidation applications such as in gas turbines components.