Reactions of diterpenoids on solid supports. I. Oxidation of methyl abietate on the sorbents Al2O3 and SiO2 containing potassium permanganate

The oxidation of methyl abietate on the sorbents Al₂O₃ and SiO₂ containing potassium permanganate has been studied. It has been shown that the following are formed under the conditions selected: compounds of the dehydroabietane series, stereoisomeric mono- and diepoxides of methyl abietate, and the products of their transformation on the sorbents. The structures and stereochemistries of the compounds isolated have been established with the aid of spectral methods and XSA.Novosibirsk Institute of Organic Chemistry, Siberian Division of the Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 371–378, May–June, 1994.     

Interaction of Hydroxylamine with Esters of 2-Oxobutenoic Acids. Synthesis of 1-Hydroxy-3-hydroximino-2-pyrrolidinones

New 3-hydroximino-1-hydroxy-2-pyrrolidinones have been synthesized by the interaction of NH₂OH and NH₂OBn with the methyl esters of 2-oxo-3-butenoic acid derivatives. Some intermediate compounds have been isolated and identified and the reaction mechanism is discussed.     

Nitrate-Citrate Sol-Gel Synthesis of Hydrated Calcium Aluminate and Sorption Materials on Its Basis

Sol-gel technique was used to develop a method for synthesis of hydrated tricalcium aluminate Ca₃[Al(OH)₆]₂ and surface-layered gas-chromatographic sorbents on its basis. The materials obtained were examined by X-ray diffraction analysis, scanning electron microscopy, X-ray fluorescence microanalysis, adsorption porosimetry, and gas chromatography. It was found that cubic Ca₃[Al(OH)₆]₂ is the main phase in the surface layer of the sorption materials. The Hammett indicator method was used to examine the acid-base properties and the variation of the content of active centers between sorbents obtained in different ways. The chromatographic retention parameters were determined for test compounds, and the polarity and selectivity of the sorbents under study was evaluated. It was shown that Chromaton N-AW modified with hydrated calcium aluminate can be used, with addition of SE-30 stationary liquid phase, to separate complex mixtures of organic compounds.     

A Study of the Zn-based Desulfurization Sorbents for H2S Removal in the IGCC

The various Zn-based sorbents were prepared by physical mixing method and co-precipitation method. The sulfur removing capacity and regeneration properties of the various sorbents were measured in fixed bed reactor at middle temperature condition (sulfidation process 480 °C, regeneration process 580 °C). The sulfur removing capacities of the sorbents were depended on the physical properties such as pore volume, surface area and particle size. The Zn-based sorbents prepared by co-precipitation method were higher pore volume, surface area and smaller particle size resulting in the higher capacities than those prepared by the physical mixing method. To improve the regeneration properties of the sorbents, the various promoters such as cobalt, iron, nickel and cerium were added to the sorbents. The promoters have various roles with the kind of promoter. The roles of promoters could be explained by heat effect and catalytic effect of the promoters. Also, the alloyed structure like spinel structure (ZnTi₂O₄) has been proposed to explain the superior regeneration properties compared to the single ZnO structure. In addition, the simultaneous removals of the H₂S and NH₃ over the Zn–Al-based sorbents were tested at 650 °C. So, the new process for simultaneous removal using the developed Zn-based sorbents could be proposed. The role of promoters, effect of hydrogen potential pressure and the deactivation mechanism including the sulfidation of metal oxide to metal sulfide were also discussed.     

Electron impact induced fragmentations of 2-chlorovinyl methyl sulphides

A series of 2-chlorovinyl methyl sulphides, CH₃SCR¹?CR²Cl (R¹, R² = H, Me, Et, t-Bu, Ph; R¹ = H, R² = CH₃) has been analysed under electron impact conditions. The most significant common fragmentations involve primary loss of Cl˙ and methyl radicals. Analysis of the phenyl-substituted derivative suggests that loss of CH₃˙ is a lower activation energy process than loss of Cl˙. The characteristic loss of CH₃SCl from the same derivative has been examined with respect to the structure of the resulting fragment by means of suitable model compounds.     

Sol-gel synthesis and sorption properties of calcium monoaluminate

Method for synthesis of calcium aluminate and sorbents based on this compound was developed on its basis of the sol-gel technology. The method makes it possible to obtain the target product with specific surface areas in the range from 7 to 120 m² g^–1. The compounds obtained were characterized by scanning electron microscopy, X-ray phase analysis, and X-ray fluorescence microanalysis. It was found that the main phase of the sorbents is rhombohedral calcium monoaluminate CaAl₂O₄. The method of Hammett indicator adsorption was used to determine the content of active centers on the surface of the sorbents and the distribution of these centers over ionization constants. It was shown that the surface characteristics of the sorbents depend on their synthesis method. The retention parameters, polarities, and thermodynamic characteristics were determined for organic compounds of various classes. The possibility of using calcium aluminate modified with sodium chloride for gas-chromatographic separation of aliphatic and aromatic hydrocarbons and carbonyl compounds was demonstrated.     

Removal of sulfur from commercial kerosene using nanocrystalline NiFe2O4 based sorbents

This paper deals with the simultaneous removal of sulfur from commercial kerosene at room temperature using sorbents containing NiFe₂O₄ nanoparticles. The nanocrystalline NiFe₂O₄ based sorbents were prepared using the combustion route. The effect of fuel content on the surface properties and desulferization activity of Ni/Fe mixed oxide sorbents has been studied.It was observed that incorporation of metal cations (Ni²⁺) into the hematite (α-Fe₂O₃) crystal structure alters the surface properties and desulferization activity of the investigated oxides, which in turn depends on the nature and concentration of the incorporated metal cation and the released heat during the combustion process. The effect of fuel content in modifying the resultant surface area could be directly related to the variations in the rate of crystal growth of the solids studied depending upon preparation temperature. Interestingly, all the prepared ferrites exhibit a narrow pore size distribution in the range of 0.9–2 nm. The capacity of NiFe₂O₄ to adsorb sulfur from commercial kerosene was evaluated in terms of their textural and chemical characteristics.     

Infrared Spectroscopic and Gravimetric Studies on the Dicyclohexylaminemetal(II) Tetracyanonickellate(II) Host-aromatic Guest Systems

Co(Cyclohexylamine)₂Ni(CN)₄ and Cd(Cyclohexylamine)₂Ni(CN)₄ host compounds have been prepared in powder form. The spectral data suggest that these complexes are similar in structure to the Hofmann-dma-type hosts. The sorption processes of the aromatic guests (benzene, toluene, o-, m-, p-xylene, naphthalene, 1,2-, 1,3-dichlorobenzene and 1,4-dibromobenzene) inthese hosts have been examined at room temperature by gravimetric and spectroscopic measurements. The desorption of the benzene guest against time has been measured. The host structures change on inclusion of the guests and recover after liberation. The host complexes have been suggested as sorbents for isomeric separations.     

2‐(2‐Naphthyloxy)acetate derivatives. I. A new class of antiamnesic agents

The title compounds 1‐(2‐naphthyloxymethylcarbonyl)piperidine, C₁₇H₁₉NO₂, (I), and 3‐methyl‐1‐(2‐naphthyl­oxy­methyl­carbonyl)­piperidine, C₁₈H₂₁NO₂, (II), are potential antiamnesics. In (II), the methyl‐substituted piperidine ring is disordered over two conformations. The piperidine ring has a chair conformation in both compounds. In (I), the mol­ecules are linked by weak intermolecular C—H⃛O interactions to give networks represented by C(4), C(6) and (18) graph‐set motifs, while in (II), weak intermolecular C—H⃛O interactions generate (5), C(4) and C(7) graph‐set motifs. The dihedral angle between the naphthalene moiety and the piperidine ring is 33.83 (7)° in (I), while it is 31.78 (11) and 19.38 (19)° for the major and minor conformations, respectively, in (II).     

Effect of MnO2 and α-Fe2O3 on organic binders degradation investigated by Raman spectroscopy

Vibrational spectroscopy and GC–MS were used to investigate the effect of MnO₂ and α-Fe₂O₃ on the degradation of methyl linoleate and vegetal and animal fatty. The metal oxides are among the most employed pigments in rock art paintings, whereas the organic compounds were used to mimic organic binders potentially used in such paintings.Both oxides were very effective in the catalytic oxidation of the organic substrates and light had no significant effect, qualitatively or quantitatively, on the final products. In the case of methyl linoleate without metal oxide, the effect of light (visible) was investigated and it was demonstrated that the samples kept in the dark produced relatively less oxidation products, although the main products were the same (hexanal, methyl 9-oxononanoate and methyl octanoate). In the presence of MnO₂ and α-Fe₂O₃ methyl 9-oxononanoate was the main product, followed by hexanal. The spectral patterns of the oxidation products were different for manganese and iron oxide and GC–MS demonstrated that more compounds are formed in the former than with α-Fe₂O₃. Vegetal and animal fatty presented the same behavior that methyl linoleate did.The results here reported indicated that the two pigments considered actively contribute to fat degradation and the presence of inorganic pigments is the main factor to take into account when organic binders degradation in rock art paintings are investigated.     

Bluish-Green BMes2-Functionalized PtII Complexes for High Efficiency PhOLEDs: Impact of the BMes2 Location on Emission Color

New phosphorescent Pt^II compounds based on dimesitylboron (BMes₂)-functionalized 2-phenylpyridyl (ppy) N,C-chelate ligands and an acetylacetonato ancillary ligand have been achieved. We have found that BMes₂ substitution at the 4′-position of the phenyl ring can blue-shift the phosphorescent emission energy of the Pt^II compound by approximately 50 nm, compared to the 5′-BMes₂ substituted analogue, without substantial loss of luminescent quantum efficiencies. The emission color of the 4′-BMes₂ substituted Pt^II compound, Pt(Bppy)(acac) ( 1 ) can be further tuned by the introduction of a substituent group at the 3′-position of the phenyl ring. A methyl substituent red-shifts the emission energy of 1 by approximately 10 nm whereas a fluoro substituent blue-shifts the emission energy by about 6 nm. Using this strategy, three bright blue-green phosphorescent Pt^II compounds 1 , 2 and 3 with emission energy at 481, 492, and 475 nm and Φ_PL=0.43, 0.26 and 0.25, respectively, have been achieved. In addition, we have examined the impact of BMes₂ substitution on 3,5-dipyridylbenzene (dpb) N,C,N-chelate Pt^II compounds by synthesizing compound 4 , Pt(Bdpb)Cl, which has a BMes₂ group at the 4′-position of the benzene ring. Compound 4 has a phosphorescent emission band at 485 nm and Φ_PL=0.70. Highly efficient blue-green electroluminescent (EL) devices with a double-layer structure and compounds 1 , 3 or 4 as the phosphorescent dopant have been fabricated. At 100 cd m⁻² luminance, EL devices based on 1 , 3 and 4 with an external quantum efficiency of 4.7, 6.5 and 13.4 %, respectively, have been achieved.     

Staudinger – Reaktionen am Bornanylen(dimethylphosphino)methylimin. Phosphorylierung des dabei gebildeten Trimethylsilylphosphinimids mit Diorganochlorphosphinen: unerwartete Bildung von Verbindungen mit P=N–P–P-Einheiten

Staudinger Reactions with Bornanylene(dimethylphosphino)methylimine. Phosphorylation of the Trimethylsilylphosphine Imide formed with Diorganochlorophosphines: unexpected Formation of Compounds with P=N–P–P Units Phosphinimido derivatives of the chiral bornanylene(dimethylphosphino)methyl imine have been obtained from its reactions with trimethylsilyl-, phenyl- and 4-nitrobenzoyl azide. A single crystal X-ray structure determination has been conducted on the 4-nitro-benzoylphosphinimido derivative of bornanylene(dimethylphosphino)methyl imine. The compound was found to crystallize with two independent molecules in the chiral monoclinic space group P2₁. The trimethylsilylphosphinimido derivative of bornanylene(dimethylphosphino)methyl imine was allowed to react with diorgano-chlorophosphines, with unexpected formation of compounds with PP-bonded RR′₂P=N–P⁽⁺⁾R″₂–PR″₂ groups. The ³¹P-NMR spectra of two representative compounds are simulated and discussed.     

An Efficient Method for Chemoselective Reduction of Nitro Compounds Using Bimetallic Fe‐Ni NPs/H3PW12O40.×H2O System

The selective reduction of nitro compounds by treatment with bimetallic Fe‐Ni nanoparticles (NPs) and tungestophosphoric acid hydrate (H₃PW₁₂O₄₀.×H₂O) in H₂O is reported. The method has been applied to a broad range of nitro compounds with different sensitive functionalities, including halides, carbonyl, hydroxyl, aldehyde, methyl, acetyl, nitrile, and ester substituents with excellent yields. The reaction yielded single product in all cases with very high yield. The simple experimental procedure and easy purification make the protocol advantageous.     

The application of solid sorbents for the purification of aluminum contaminated chemicals used as modifiers in electrothermal atomic absorption spectrometry

Various microcolumns with solid sorbents (ion exchange resins, functionalised cellulose sorbents, chelating resins) have been tested with respect to their ability for the purification of aluminum contaminated chemicals used as modifiers in electrothermal atomic absorption spectrometry. The purification of NaNO₃, Mg(NO₃)₂, K₂SO₄ and (NH₄)₂HPO₄ has been the most effective with an almost 100% efficiency, when Spheron-Oxine was used as chelating resin. The sorption of aluminum from KOH solution has been found to be very high (around 90%) for all investigated sorbents. However, the best results have been obtained with anion-exchange resins. It has been difficult to purify concentrated mineral acids (HCl, H₂SO₄). A retention of aluminum above 80% has been achieved only when Cellex P, Chelex 100 or Amberlite XAD-2 have been used.     

Effects of alumina phases on CO2 sorption and regeneration properties of potassium-based alumina sorbents

A range of potassium-based alumina sorbents were fabricated by impregnation of alumina with K₂CO₃ to examine the effects of the structural and textural properties of alumina on the CO₂ sorption and regeneration properties. Alumina materials, which were used as supports, were prepared by calcining alumina at various temperatures (300, 600, 950, and 1,200 °C). The CO₂ sorption and regeneration properties of these sorbents were examined during multiple tests in a fixed-bed reactor in the presence of 1 vol% CO₂ and 9 vol% H₂O. The regeneration capacities of the potassium-based alumina sorbents increased with increasing calcination temperature of alumina. The formation of KHCO₃ increased with increasing calcination temperature during CO₂ sorption, whereas the formation of KAl(CO₃)(OH)₂, which is an inactive material, decreased. These results is due to the fact that the structure of alumina by the calcination temperature is related directly to the formation of the by-product [KAl(CO₃)(OH)₂]. The structure of alumina plays an important role in enhancing the regeneration capacity of the potassium-based alumina sorbent. Based on these results, a new potassium-based sorbent using δ-Al₂O₃ as a support was developed for post-combustion CO₂ capture. This sorbent maintained a high CO₂ capture capacity of 88 mg CO₂/g sorbent after two cycles. In particular, it showed a faster sorption rate than the other potassium-based alumina sorbents examined.     

Direct aqueous injection gas chromatographic analysis of polar compounds using sorbents containing potassium fluoride dihydrate

Summary For direct aqueous injection gas-chromatographic analysis of polar compounds present in aqueous solutions sorbents containing conventional stationary phases and potassium fluoride crystal hydrate are proposed. On such sorbents polar compounds elute with narrow symmetrical zones under gentle chromatographic conditions. In such sorbents KF.2H₂O mainly deactivates the surface of the solid support. The polarity of these sorbents is compared with the polarity of molten potassium fluoride dihydrate and conventional stationary phases.     

Infrared spectroscopic and gravimetric studies on the cyclopropylaminemetal(II) tetracyanonickellate(II) host–aromatic guest systems

The host complexes M(Cyclopropylamine)₂Ni(CN)₄ (M = Co or Cd) have been prepared in powder form. The spectral data suggest that the structures of these compounds are similar to those of the Hofmann-type hosts. The absorption and the liberation processes of the aromatic guests (benzene, toluene, 1,2-dichlorobenzene, o-xylene, m-xylene and p-xylene) in these hosts have been examined at room temperature by gravimetric and spectroscopic measurements. The desorption of the benzene guest against time has been measured. The host structures do not change on inclusion and liberation of the guest. The host compounds have been suggested as sorbents for isomeric separations.     

Cycloaddition in Condensed Isoindoles. 2. Method for Obtaining New Derivatives of 2-Phenylpyridine

The reaction of pyrido[2,1-a]isoindole with maleimide derivatives has been investigated. A new rearrangement has been found, the products of which are 2-[2'-(1-R-2,5-dioxopyrrolidinidene)-2'-(1-R-2,5-dioxopyrrolidinyl)methyl]phenylpyridines. A probable mechanism for the rearrangement has been proposed. The existence of atropoisomerism for the compounds obtained has been demonstrated by ¹H NMR spectra.     

FT-IR study on CO<Subscript>2</Subscript> adsorbed species of CO<Subscript>2</Subscript> sorbents

The stability of amine-functionalized silica sorbents prepared through the incipient wetness technique with primary, secondary, and tertiary amino organosilanes was investigated. The prepared sorbents were exposed to different gaseous streams including CO₂/N₂, dry CO₂/air with varying concentration, and humid CO₂/air mixtures to demonstrate the effect of the gas conditions on the CO₂ adsorption capacity and the stability of the different amine structures. The primary and secondary amine-functionalized adsorbents exhibited CO₂ sorption capacity, while tertiary amine adsorbent hardly adsorbed any CO₂. The secondary amine adsorbent showed better stability than the primary amine sorbent in all the gas conditions, especially dry conditions. Deactivation species were evaluated using FT-IR spectra, and the presence of urea was confirmed to be the main deactivation product of the primary amine adsorbent under dry condition. Furthermore, it was found that the CO₂ concentration can affect the CO₂ sorption capacity as well as the extent of degradation of sorbents.     

Characterization of five [C4H7O]+ Ion structures. Fragmentation of the 2-pentanone molecular ion

The [C₄H₇0]⁺ ions [CH₂?CH? C(?OH)CH₃]⁺ (1), [CH₃CH?CH? C(?OH)H]⁺ (2), [CH₂?C(CH₃)C(?OH)H]⁺ (3), [Ch₃CH₂CH₂C?O]⁺ (4) and [(CH₃)₂CHC?O]⁺ (5) have been characterized by their collision-induced dissociation (CID) mass spectra and charge stripping mass spectra. The ions 1–3 were prepared by gas phase protonation of the relevant carbonyl compounds while 4 and 5 were prepared by dissociative electron impact ionization of the appropriate carbonyl compounds. Only 2 and 3 give similar spectra and are difficult to distinguish from each other; the remaining ions can be readily characterized by either their CID mass spectra or their charge stripping mass spectra. The 2-pentanone molecular ion fragments by loss of the C(1) methyl and the C(5) methyl in the ratio 60:40 for metastable ions; at higher internal energies loss of the C(1) methyl becomes more favoured. Metastable ion characteristics, CID mass spectra and charge stripping mass spectra all show that loss of the C(1) methyl leads to formation of the acyl ion 4, while loss of the C(5) methyl leads to formation of protonated vinyl methyl ketone (1). These results are in agreement with the previously proposed potential energy diagram for the [C₅H₁₀O]⁺˙ system.