Euphorstranoids A and B, Two Highly Rearranged Ingenane Diterpenoids from Euphorbia stracheyi: Structural Elucidation, Chemical Transformation, and Lipid-Lowering Activity

Euphorstranoids A (1) and B (2), two highly rearranged ingenane diterpenoids with an unusual 5/6/7/3 carbon ring system, were isolated from Euphorbia stracheyi. Their structures were determined by a combination...

Thermodynamic Studies and Optimization of the Method for Obtaining Neodymium Fluoride for the Production of Magnetic Sensors’ Sensitive Elements

Rare earth metals (REM) with magnetic properties find application in the recently developed high-tech industries. Sensor magnetic systems based on neodymium are increasingly in demand in modern engineering and geological surveys due to their favorable combination of properties of magnetic materials based on rare earth metals. One of the problems is to obtain high-quality materials for the production of such magnetic sensors. It should be noted that the high activity of REM does not allow obtaining master alloys and REM-based alloys from metallic materials; it is advisable to use halide compounds. This work discusses a method for producing neodymium fluoride from its oxide. REM fluorides can be obtained by fluorinating the oxides of these metals. Various fluorine-containing compounds or elemental fluorine are usually used as fluorinating reagents, which have their own advantages and disadvantages. The thermodynamic and technological analysis of neodymium fluoride production processes has shown the most acceptable fluorinating agent is ammonium hydrofluoride, which was used in this work. In order to increase the productivity and degree of chemical transformation, it was proposed to perform heating stepwise; i.e., at the initial stage, heat at a speed of 3 degrees per minute, after which the heating speed was reduced to 2 degrees per minute, and finally the speed was reduced to 1 degree per minute. Due to proposed heating mode, the same productivity and yield of chemical transformation were achieved, with an increased efficiency up to 30%, which can significantly reduce the cost of production. The obtained product is used in the production of neodymium-based alloys by metallothermic reduction of a mixture of fluorides. The sensor material obtained in this way is characterized by a low (less than 0.05%) oxygen content.

Chemical Transformation of α-Pinene derived Organosulfate via Heterogeneous OH Oxidation: Implications for Sources and Environmental Fates of Atmospheric Organosulfates

Organosulfur compounds are found to be ubiquitous in atmospheric aerosols — a majority of which are expected to be organosulfates (OSs). Given the atmospheric abundance of OSs, and their potential to form a variety of reaction products upon ageing, it is imperative to study the transformation kinetics and chemistry of OSs to better elucidate their atmospheric fates and impacts. In this work, we investigated the chemical transformation of an α-pinene derived organosulfate (C10H17O5SNa, αpOS-249) through heterogeneous OH oxidation at a relative humidity of 50 % in an oxidation flow reactor (OFR). The aerosol-phase reaction products were characterized using the high-performance liquid chromatography-electrospray ionization-high resolution mass spectrometry and the ion chromatography. By monitoring the decay rates of αpOS-249, the effective heterogeneous OH reaction rate was measured to be (6.72 ± 0.55) × 10−13 cm3 molecule−1 s−1. This infers an atmospheric lifetime of about two weeks at an average OH concentration of 1.5 × 106 molecules cm–3. Product analysis shows that OH oxidation of αpOS-249 can yield more oxygenated OSs having a nominal mass-to-charge ratio (m/z) at 247 (C10H15O5S−), 263 (C10H15O6S−), 265 (C10H17O6S−), 277 (C10H13O7S−), 279 (C10H15O7S−), and 281 (C10H17O7S−). The formation of fragmentation products, including both small OSs (C < 10) and inorganic sulfates, is found to be insignificant. These observations suggest that functionalization reactions are likely the dominant processes and that multigenerational oxidation possibly leads to formation of products with one or two hydroxyl and carbonyl functional groups adding to αpOS-249. Furthermore, all product ions except m/z = 277 have been detected in laboratory generated α-pinene derived secondary organic aerosols as well as in atmospheric aerosols. Our results reveal that OSs freshly formed from the photochemical oxidation of α-pinene could react further to form OSs commonly detected in atmospheric aerosols through heterogeneous OH oxidation. Overall, this study provides more insights into the sources, transformation, and fate of atmospheric OSs.