The electronic nature of substituents present in 1,4-dimethoxybenzene derivatives has been found to have a profound effect on whether or not such substrates can be oxidized to diquinones using ceric ...ammonium nitrate (CAN). In particular, there appears to be a correlation between the Hammett σ
p
value of a substituent and the yield of the corresponding diquinone obtained upon treatment of the dimethoxybenzene derivative with CAN. This information could aid in the prediction of whether or not a given substrate would be expected to produce a diquinone upon such oxidation.
A new and practical strategy for chemo‐ and regioselective ortho‐nitration of aniline carbamates under mild and neutral conditions have been disclosed using ceric ammonium nitrate (CAN) as a cheap ...nitrating agent. The electrophilic reaction exhibits a simple and straightforward pathway to obtain exclusively ortho‐nitration products in good to excellent yields with outstanding functional groups tolerance for both electron rich and highly electron‐deficient anilines. The highlight of this protocol is the role of ceric ammonium nitrate (CAN) as a cheap nitrating agent that (Ce+4) via chelation with the directing group controls the regioselectivity of electrophilic nitration without the requirement of additional metal catalyst and external oxidant.
A new and practical strategy for ceric ammonium nitrate promoted highly chemo‐ and regioselective ortho‐nitration of aniline carbamates has been developed under mild and neutral conditions without the requirement of additional catalyst and oxidant. Both electron rich and highly electron‐deficient anilines afforded good to excellent yields of the desired products with outstanding functional groups tolerance.
Reinforcing agents and accelerators are the most important auxiliaries for rubber industry. In this paper, ceric ammonium nitrate (CAN), for the first time, worked as a catalyst for hydroxyl groups ...in silica to prepare silica grafted sodium xanthate (SSX), which was used as an in-situ modified multifunctional rubber additive in this work. Compared with sodium isobutyl xanthate (SIBX), SSX has enhanced the initial and final degradation temperatures, achieving the improvement of 103 °C and 277 °C, respectively. Notably, owing to the powerful interaction between each component, SSX can be homogeneously dispersed in the natural rubber (NR) matrix in contrast to the seriously aggregated silica. Meanwhile, NR/SSX composites exhibited superior curing properties and showed an increase of 29.1% and 33.4% in the tensile strength and tear strength, respectively, compared to that of traditional 2-mercaptobenzothiazole (MBT) system. Since high-performance rubber composites can be obtained by introducing SSX, we believe that this work can provide a novel and facile approach to prepare natural silicate minerals-based vulcanization accelerators.
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•Compared with traditional accelerators, SSX is an eco-friendly accelerator.•SSX can be better dispersed in the rubber matrix and improve the thermal stability of the xanthate.•Due to the excellent vulcanization and reinforcement effect, the mechanical properties of NR/SSX composites are greatly improved.
Chiral α-aryl glycines play a key role in the preparation of some bioactive products, however, their catalytic asymmetric synthesis is far from being satisfactory. Herein, we report an efficient ...nickel-catalyzed asymmetric hydrogenation of N-aryl imino esters, affording chiral α-aryl glycines in high yields and enantioselectivities (up to 98% ee). The hydrogenation can be conducted on a gram scale with a substrate/catalyst ratio of up to 2000. The obtained chiral N-p-methoxyphenyl α-aryl glycine derivatives are not only directly useful chiral secondary amino acid esters but can also be easily deprotected by treatment with cerium ammonium nitrate for further transformations to several widely used molecules including drug intermediates and chiral ligands. Formation of a chiral Ni-H species in hydrogenation is detected by
H NMR. Computational results indicate that the stereo selection is determined during the approach of the substrate to the catalyst.
Abstract
A Cerium(IV)‐promoted phosphinoylation‐nitratation of alkenes is established under mild conditions. In this process, Ceric ammonium nitrate (CAN) acts as a cheap phosphorus‐radical ...initiator, as well as a nitrate donor. Various β‐nitrooxyphosphonates are delivered in high yield in a one‐pot manner.
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A promising and useful method has been accomplished for regio‐ and diastereoselective synthesis of tetrahydro‐benzofuro3,2‐cchromenones through ceric(IV) ammonium nitrate (CAN) mediated oxidative ...coupling of cyclic/acyclic 1,3‐dicarbonyl compounds to 2‐aryl/heteroarylchromenes followed by a base assisted cyclization. The significant features of the method encircle easy accessibility of the starting materials, high air stability and low toxicity of oxidant CAN, high product yield, operationally simple and eco‐friendly reaction conditions. Trapping of a radical intermediate with radical scavenger TEMPO (detected by LC–MS) from the reaction mixture proved that the oxidative coupling is a radical mediated process.
Nitrogen (N) is an essential nutrient for crop growth, and its different forms have a significant impact on crop uptake and various physiological processes that underpin yield and quality. Although ...many studies suggesting that a combination of ammonium (NH4+) and nitrate (NO3-) can enhance crop outcomes, the optimal ammonium-nitrate ratio (ANR) for different crops remains uncertain due to a lack of extensive validation with large datasets.
This paper collected 151 peer-reviewed studies (with 2417 observations) on the effects of ANR on crop growth published from 1972 to 2022. The comprehensive effects of different ANRs on crop yield and quality (protein, vitamin C, starch etc.) of various crops were evaluated via meta-analysis to provide an optimal N management strategy.
Our analysis identified rice as an ammonium-preferred crop, and the ANR of 75:25 shows the most effective improvement in total biomass and photosynthetic characteristics at seedling age, with a 26.0% increase in the biomass and a 21.9% boost in chlorophyll content compared to pure ammonium treatment. Wheat and tobacco can be considered ammonium-nitrate-balanced crops, and a balanced ANR of 50:50 resulted in significant synergistic improvement in both yield and quality, i.e., wheat biomass and protein increased by 13.3% and 7.1%, respectively, and tobacco yield significantly increased by 21.9%, compared to pure nitrate supply. In contrast, maize, soybeans, and vegetables were identified as nitrate-preferred crops, applying pure ammonium or an excess of ammonium-N over nitrate led to a significant reduction in yield and quality, with the most pronounced inhibitory effect observed in soybeans. However, a slight supplement of ammonium can also promote the growth of these crops. Furthermore, soil pH significantly influences the preference for ammonium and nitrate. In soils with an acidic environment, crops tend to efficiently utilize nitrate, whereas in alkaline conditions, there is a preference for an increased presence of ammonium.
The combination of ammonium and nitrate in appropriate ratio can improve multiple agronomic characteristics both for ammonium-preferred and nitrate-preferred crops, which may due to complementary physiological functions of two forms of N. Among various soil factors, soil pH showed significant influence on determining the optimal ANR and should be taken into consideration.
These findings reveal that the appropriate ANR is crucial for both crop yield and quality improvement and should be fully valued in future nutrient management.
•Rice is an ammonium-preferred crop with optimal ANR of 75:25.•.Wheat and tobacco can be considered ammonium-nitrate-balanced crops.•.Maize, soybeans, and vegetables are nitrate-preferred crops.•Soil pH greatly affects the ammonium-nitrate preference.•Appropriate ANR is crucial for both crop yield and quality improvement.
Wintertime ammonium nitrate aerosol pollution is a severe air quality issue affecting both developed and rapidly urbanizing regions from Europe to East Asia. In the United States, it is acute in ...western basins subject to inversions that confine pollutants near the surface. Measurements and modeling of a wintertime pollution episode in Salt Lake Valley, Utah, demonstrate that ammonium nitrate is closely related to photochemical ozone through a common parameter, total odd oxygen, Ox,total. We show that the traditional nitrogen oxide and volatile organic compound (NOx‐VOC) framework for evaluating ozone mitigation strategies also applies to ammonium nitrate. Despite being nitrate‐limited, ammonium nitrate aerosol pollution in Salt Lake Valley is responsive to VOCs control and, counterintuitively, not initially responsive to NOx control. We demonstrate simultaneous nitrate limitation and NOx saturation and suggest this phenomenon may be general. This finding may identify an unrecognized control strategy to address a global public health issue in regions with severe winter aerosol pollution.
Plain Language Summary
Particulate matter (PM) is dangerous to human health and impacts visibility and climate. In the United States, Europe, and Asia, PM is severe in urban areas in the winter when ammonium nitrate, NH4NO3, comprises an appreciable fraction of the total PM mass. A key control strategy is to reduce emissions of the limiting reagent. Using measurements from a recent field campaign in the Salt Lake Valley, Utah, which experiences high PM levels in winter, we demonstrate that emission control strategies can be evaluated using the same framework commonly used to control ozone, another common pollutant that occurs at high levels in urban areas in the summer. We show that initial control of the NOx precursor is ineffective at reducing NH4NO3 aerosol in the Salt Lake Valley, while initial control of volatile organic compounds, which are not a direct precursor for either nitrate or ammonium, is effective due to their influence on oxidation cycles. This finding differs from many mitigation strategies in the western United States and may also be relevant to other regions in Europe and Asia which experience high wintertime PM.
Key Points
Wintertime ammonium nitrate aerosol pollution is closely tied to photochemical ozone production through a common parameter, Ox,total
Box modeling reveals ammonium nitrate formation in the Salt Lake Valley is nitrate‐limited but NOx‐saturated
Mitigation strategies that focus on NOx control in some wintertime‐polluted layers may initially increase ammonium nitrate
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