Hydrogen absorption by intermetallics M2Fe (M = Zr,Hf, Ti) and their effect on the catalytic aromatization of ethane

The absorption properties of the hydride-forming intermetallics M₂Fe(M = Zr, Hf, Ti) and their effect on the aromatization of ethane over Pt,Ga/HCVM catalyst within the temperature range 400–450 °C are studied. The absorption capacity of the intermetallics under aromatization conditions and their efficiency as hydrogen acceptors are shown to decrease in the order Zr₂Fe > Ti₂Fe > Hf₂Fe.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1726–1729, October, 1994.     

Withasteroids ofPhysalis VI.1H and13C NMR spectra of withasteroids ixocarpalactone A and ixocarpanolide

The¹H and¹³C NMR spectra of two withasteroids isolated fromPhysalis ixocarpa Brot. have been studied in detail. Their spectral characteristics are discussed. A comparison of the results obtained has led to the identification of a withasteroid with the composition C₂₈H₄₀O₈, mp 291–292°C (from methanol) as ixocarpalactone A, in spite of some difference in its physical constants. The other compound, with mp 252–253°C (from methanol), had the composition C₂₈H₄₀O₆, [] _D ²⁰ +27±4°, is new and has been called ixocarpanolide. The structure of 5,20R-dihydroxy-1-oxo-6, 7-epoxy-22R-witha-2-enolide has been proposed for it.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 326–332, May–June, 1986.     

IR spectra of catalysts and adsorbed molecules. 39. Acid and catalytic properties of pentasils modified with platinum,chromium, and zinc

It was shown that when platinum is incorporated in pentasil (HZSM), the concentration of L sites increases by 2 times with no change in the number of B sites; in Pt-Cr-containing catalysts, the concentration of L sites passes through a maximum with a 0.72% concentration of Cr, and the number of OH groups and B sites decreases. The concentration of B sites decreases and the concentration of L sites increases in samples simultaneously promoted with Pt, Cr, and Zn. In conditions of aromatization of lower alkanes on Pt-Cr-containing catalysts, the concentration of OH groups and B sites decreases, while the concentration of L sites increases. Incorporation of platinum in HZSM increases the aromatizing activity with respect to methane, and additional incorporation of chromium and zinc increases the yield of aromatic hydrocarbons from ethane and propane also.See [1] for communication 38.Deceased.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 5, pp. 1038–1042, May, 1992.     

Properties of pentasil-containing catalysts in hydrocarbon conversions. 7. Benzene alkylation by lower alkanes in the presence of modified zeolites

A novel catalytic synthesis of alkylaromatic hydrocarbons (AArH) containing C₇-C₈ has been achieved using C₂-C₄, alkanes as alkylating reagents on high silica zeolites of the pentasil type. It has been established that the yield of AArH during the reaction between benzene and alkanes varies in the order C₂H₆3H₈C₄C₁₀ (450–600°C). Modification of the zeolite by additions of Pt, Zn, and Ga results in a lowering of the reaction temperature (by 100°C) and alters the selectivity of the alkylation process. On passing from flow to static conditions and raising the pressure to 2–4 MPa the AArH yield doubles and reaches 70–75% in the case of C₃-C₄ hydrocarbons.For previous communication, see [1].Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2228–2232, October, 1991.     

Withasteroids ofPhysalis. VII. 14α-Hydroxyixocarpanolide and 24,25-expoxywithanolide D

Two new withasteroid have been isolated fromPhysalis angulata L. — 14α-hydroxyixocarpanolide and 24,25-epoxywithanolide D. 14α-hydroxyixocarpanolide — C₂₈H₄₀O₇, mp 245–250°C (from methanol), [α] _D ²⁰ +29±2° (chloroform). 24,25-Epoxywithanolide D — C₂₈H₃₈O₇, mp 257–261°C (from methanol, [α] _D ²⁰ +23±2° (chloroform). On the basis of its UV, IR, CD, mass, and¹H and¹³C NMR spectra the structure of 5α,14α,20R-trihydroxy-1-oxo-6α,7α-epoxy-22R-2itha-2-enolide is suggested for 14α-hydroxyixocarpanolide. On the basis of spectral characteristics and the preparation of 4β-acetoxy and 4-oxo derivatives of 24,25-epoxywithanolide D, the structure of 4β,20R-dihydroxy-1-oxo-5β,6β;24S,25S-diepoxy-22R-witha-2-enolide is proposed for it.     

A New Extraction System Based on Isopropyl Salicylate and Trioctylphosphine Oxide for Separating Alkali Metals

It was established that isopropyl salicylate can be used similarly to 1,3-diketones as a key component for a new efficient extraction system for selective separation of alkali metal cations. According to DFT modeling of complexes of isopropyl salicylate and 1,3-diketone with alkali metal cations (Li⁺, Na⁺, K⁺), six-membered metallacycles are formed whose stability decreases along the series Li > Na > K, which results in the observed enhanced affinity to lithium. The extraction ability of isopropyl salicylate is manifested in the presence of trioctylphosphine oxide (TOPO). The newly obtained complexes of isopropyl salicylate with alkali metal cations as well as their extracts in a mixture with TOPO are characterized by means of FT-IR, Raman, and NMR spectroscopy. The probable structure of the extracted lithium complex is presumed and the role of TOPO in the extraction process is investigated in detail. Extraction experiments showed extremely high separation coefficients for Li/Na and Li/K pairs in the extraction from a model multi-component solution.     

In-Electrospray source Hydrogen/Deuterium exchange coupled to multistage fragmentation for the investigation of the protonation and fragmentation pathways of gas phase ions

Identification of molecules in complex natural matrices relies on matching the fragmentation spectra of ions under investigation and the spectra acquired for the corresponding analytical standards. Currently, there are many databases of experimentally measured tandem mass spectrometry spectra (such as NIST, MzCloud, and Metlin), and considerable progress has been made in the development of software for predicting tandem mass spectrometry fragments in silico using combinatorial, machine learning, and quantum chemistry approaches (such as MetFrag, CFM-ID, and QCxMS). However, the electrospray ionization molecules can be ionized at different sites (protonated or deprotonated), and the fragmentation spectra of such ions are different. Here, we are using the combination of the in-ESI source hydrogen/deuterium exchange reaction and MSⁿ fragmentation for the investigation of the fragmentation pathways for different protomers of organic molecules. It is shown that the distribution of the deuterium in the fragment ions reflects the presence of different protomers. For several molecules, the distribution of deuterium was traced up to the MS⁵ level of fragmentation revealing many unusual and unexpected effects. For example, we investigated the loss of HF from the ciprofloxacin and norfloxacin ions and observed that for ions protonated at –COOH group, the eliminating hydrogen always comes from –NH group. When ions are protonated at another site, the elimination of hydrogen with a probability of 30% occurs from the –NH group, and with a probability of 70%, it originates from other sites on the molecule. Such effects were not described previously. Quantum chemical simulation was used for the verification of the protonated structures and simulation of the corresponding fragmentation spectra.