Selective alkylation of xylenes by alcohols on zeolite catalysts

The peculiarities of catalytic performance of crystalline aluminosilicates of different types and compositions (X, Y including dealuminated Y, mordenite, pentasil ZSM-5), as well as of amorphous aluminosilicate catalyst in conversion of xylene + alcohol mixtures were studied. New data were obtained for alkylation ofo-xylene withtert-butyl alcohol, concerning controlling the selectivity and stability of the zeolite catalysts in reactions proceeding with the participation of water, including the water evolved during the reaction, in particular by controlling the acidic properties and hydrophobycity of the zeolites. A catalyst ensuring production of 1,2-dimethyl-4-tert-butylbenzene (DMTBB) with a 94% yield and selectivity of alcohol conversion to the target product of 94–97% was developed. The catalyst can be used as the basis for a high-performance and environmentally safe method for the synthesis of DMTBB. The catalysts developed can be also used for selective alkylation ofo-xylene by C₃-C₅ alcohols and for alkylation ofm-xylene bytert-butyl alcohol.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No, 12, pp, 2912–2917, December, 1996.     

Physicochemical properties of Ti-grafted SBA-15

Partial oxidation of n-heptane to syngas at 400–450°C was investigated over Rh and Rh-Ni based catalysts. The Rh/-Al₂O₃ catalyst exhibited much better catalytic activity than the Rh-Ni/-Al₂O₃ catalyst. A combination of the Rh-based catalyst with the WGS reaction catalyst (Fe₃O₄—Cr₂O₃) increases the hydrogen selectivity but has no distinct effect on shifting the balance of the partial oxidation of n-heptane.This revised version was published online in December 2005 with corrections to the Cover Date.     

Essential Oils of Two Hypericum Species from Uzbekistan

The water-distilled essential oils from aerial parts of two Hypericum species (Hypericaceae) have been analyzed by GC/MS. The main components of the essential oils of Hypericum scabrum L. were -pinene -11. 2%; spathulenol - 7.2%; p-cymene - 6.1%; acetophenone - 4.8%; carvacrol - 4.7%. The essential oil of Hypericum perforatum L. contains as the main components -caryophyllene - 11.7%; caryophellene oxide -6.3%; spathulenol - 6.0%; -pinene - 5.0%.     

Selective Iridium‐Catalyzed Alkylation of (Hetero)Aromatic Amines and Diamines with Alcohols under Mild Reaction Conditions

Selective amine alkylation : A P,N‐ligand‐stabilized iridium complex has been used as an efficient catalyst for the alkylation of (hetero)aromatic amines with alcohols at mild reaction temperatures and catalyst loadings as low as 0.1 mol % Ir (see scheme). The excellent selectivity of the catalyst for monoalkylation of the amine function has also been exploited for the N,N′‐dialkylation of diamines in both symmetric and nonsymmetric fashions.

     

Deep oxidation in propane oxidative dehydrogenation to propene over V2O5/γ-Al2O3 studied by in-situ DRIFTS

In-situ DRIFTS was used to study the deep oxidation of propane, a side reaction during propane oxidative dehydrogenation to propene. Strong adsorption of propene was supposed to be the main reason for the deep oxidation. It was found that gaseous oxygen in the feed and the reaction temperature had great influence on the reaction. To obtain a relative high selectivity to propene, the reaction temperature should be maintained at 150250 °C with a proper content of gaseous oxygen in the feed for a certain catalyst and some modifiers which could weaken the adsorption of propene on the catalyst surface would be favorable.     

CO2‐promoted Water‐medium Ullmann Reaction over a Pd/Phenyl‐SBA‐15 Mesoporous Catalyst

Water‐medium Ullmann reaction was carried out in CO₂ atmosphere over the mesoporous Pd/Ph‐SBA‐15 catalyst exhibiting high activity and selectivity owing to the uniform dispersion of Pd particles and hydrophobilic mesoporous channels which facilitate the diffusion and adsorption of organic molecules, especially in an aqueous medium. The CO₂ also shows promoting effect on activity and selectivity, which could be understood by considering the role of H⁺ in the mechanism of Ullmann reaction. The optimum Ph‐Ph yield (84.0%) was obtained at p=0.8 MPa and V=6.0 mL and could remain almost unchanged even after the catalyst has been used repetitively for 5 times.     

Direct anodic oxidation ofp-methoxytoluene in methanol. The effect of electrolysis conditions

The effect of anions of the supporting electrolyte (F^–, dialkylphosphate, TsO^–, and BF ₄ ^– and other electrolysis conditions (anode material, temperature, substrate concentration) on the selectivity of the direct anodic oxidation ofp-methoxytoluene in methanol into 4-methoxybenzaldehyde dimethylacetal was studied. The highest selectivity was obtained in the presence of fluoride anion.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 524–527, March, 1995.This work was financially supported by the Ministry of Science, High School and Technical Policy of the Russian Federation within the scope of the State scientific-technical program Ecologically harmless processes of chemistry and chemical technology (project No. 1.140 Low-tonnage chemical products) and by the International Science Foundation (Grant Ch-2-1246-0923).     

Hydrogenation on Granular Palladium-containing Catalysts: I. Hydrogenation of Tertiary Acetylene Alcohols

Commercial granular palladium catalyst (0.5% of Pd on -Al₂O₃) was modified by treating with zinc acetate (type 1) or successively with zinc acetate and ammonia (type 2). The treatment significantly increased the hydrogenation selectivity for a triple bond into a double bond: to 85.3-93.1% with the type 1 catalyst and to 96.3-97.8% with the type 2 catalyst. A construction of an autoclave with a fixed bed of the granular catalyst is described.     

Quantum Mechanical Study of the Syn and Anti Conformations of Solvated Cyclic GMP

Self-consistent Reaction Field (SCRF) computational methods have been applied to guanosine 3:5-cyclic monophosphate (cGMP) to determine the geometries and energetics of the syn and anti conformations of this cyclic nucleotide in aqueous solution. The syn conformation of cGMP has been predicted to be more stable in the gas phase due to an internal hydrogen bond. The syn conformation is observed in the crystal structure of the sodium tetrahydrate salt, although a bridging water molecule is present in lieu of the internal hydrogen bond. In the gas phase, we find from Hartree–Fock/6-31+G(d) optimizations that the syn conformation is more stable than the anti by about 4 kcal/mol. However, we report here that the anti conformation is more stable in aqueous solution, according to estimates based upon results from both the Onsager model and the Isodensity Polarized Continuum Method (IPCM). Our best estimate from single-point IPCM B3LYP/6-31+G(d) calculations has the anti conformation 19 kcal/mol lower in energy. For comparison purposes, we also present SCRF results for syn and anti adenosine 3:5-cyclic monophosphate (cAMP). For cAMP, we estimate the anti conformation to be more stable than the syn by about 6 kcal/mol. We suggest that the relative stability of the anti conformation of cGMP be considered in studies, such as, enzyme docking.     

N-methyI-N-(triethoxysilylmethyl) andN-methyl-N-(silatran-1-ylmethyl) substituted glycine and alanine

Organosilicon derivatives of glycine, - and -alanine, and -methylalanine were prepared by the reaction of methyl esters of - and -halocarboxylic acids withN-methylaminomethyltriethoxysilane in the presence of triethylamine. The compounds synthesized were converted into the correspondingN-silatran-l-ylmethyl derivatives. Trimethylsilyliodoacetate reacts withN-methylaminomethyltrietoxysilane to give 2,2-diethoxy4-methyl-1-oxa-4-aza-2-silacyclohexane-6-one. Its reaction with triethanolamine leads toN-methyl-N-(silatran-l-ylmethyl)glycine.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 341–343, February, 1995.     

Simultaneous Determination of Nine Flavonoids in Dalbergia odorifera by LC

A rapid and accurate HPLC method has been developed for the simultaneous determination of nine major flavonoids, namely 3-hydroxymelanettin, melanettin, stevenin, butein, isoliquiritigenin, dalbergin, 2,4-dihydroxy-5-methoxybenzophenone, pinocembrin, 4-methoxydalbergione in Dalbergia odorifera. The samples were separated on an Aglient Zorbax SB-C₁₈ column (250 × 4.6 mm, 5 m) with a gradient of acetonitrile and 1% aqueous acetic acid (/) at a flow rate of 1.0 mL min^–1 and detected at 350 nm. The complete separation was obtained within 30 min for the nine target flavonoids. All calibration curves showed good linearity (r² > 0.999) within test ranges. The repeatability was evaluated by intra- and inter-day assays and RSD values were less than 4.0%. The recoveries were between 92.0% and 104.5%. The developed method was successfully applied to the analysis of 32 commercial samples of D. odorifera.     

Synthesis and properties of iron(II) and iron(III) complexes with 3-(α,γ-dicarboxy-n-propylidene-hydrazino)-5,6-diphenyl-1,2,4-triazine (DCPT)

Summary Proton-ligand formation constants ofDCPT and metal-ligand formation constants of its complexes with Fe(II) and Fe(III) have been determined potentiometrically at 10, 20, 30, and 40°C in 75% (v/v) dioxane-water at 0.10M ionic strength (KNO₃). The thermodynamic parameters G, H, and S have also been evaluated. The possibility of formingM(HL),M(HL)₂, andM(HL)₃ species was substantiated from potentiometric and electronic absorption measurements. The values of the stability constants logK _M(HL), log , and log derived from the spectrophotometric method are in good agreement with those obtained from potentiometric data. The use ofDCPT as an analytical reagent for the spectrophotometric determination of iron is discussed. The solid complexes have been characterized by chemical analysis and magnetic susceptibility, IR, NMR, and electronic spectral data.

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Synthese und Eigenschaften von Eisen(II)- und Eisen(III)-Komplexen mit 3-(,-Dicarboxy-n-propylidene-hydrazino)-5,6-diphenyl-1,2,4-triazin (DCPT)

Zusammenfassung Die Bildungskonstanten sowohl vonDCPT als auch seiner Komplexe mit Fe(II) und Fe(III) wurden bei 10, 20, 30 und 40°C in Dioxan-Wasser (75% (v/v)) bei einer lonenstärke von 0.1M KNO₃ potentiometrisch bestimmt. Zusätzlich wurden die thermodynamischen Parameter G, H und S ermittelt. Die Wahrscheinlichkeit des Auftretens von Komplexen der ArtM(HL),M(HL)₂ undM(HL)₃ wurde mittels potentiometrischer und absorptionsspektroskopischer Messungen erhärtet. Nach beiden Methoden ermittelte Stabilitätkonstanten stimmen gut überein. Die Verwendung vonDCPT als analytisches Reagens zur spektrophotometrischen Eisenbestimmung wird diskutiert. Die Komplexe konnten in Substanz hergestellt werden und wurden durch chemische Analyse und über ihre magnetischen und spektroskopischen Eigenschaften charakterisiert.

     

Substrate and Positional Selectivity in Electrophilic Substitution Reactions of Pyrrole, Furan, Thiophene, and Selenophene Derivatives

The relative reactivity (substrate selectivity) of five-membered heterocycles on electrophilic substitution (pyrrole >> furan > selenophene > thiophene) and their positional selectivity (furan > selenophene thiophene > pyrrole) are not consistent. The indicated differences in positional selectivity ( : ratios) of the parent heterocycles show up essentially in orientation on electrophilic substitution reactions of their derivatives and the corresponding benzannelated systems. It was shown that the positional selectivity was reduced in a sequence corresponding to the change in relative stability of the onium states of the elements (O⁺ < Se⁺ S⁺ < N⁺) and reflects the predominant role of the heteroatoms in stabilizing the -complexes formed on -substitution, in which the positive charge is distributed between the heteroatom and one -carbon atom (in -isom ers four atoms of the ring participate in delocalization of the charge). This interpretation was confirmed by quantum-chemical calculations carried out by the RHF/6-31G(d), MP2/6-31G(d)//RHF(6)-31G(d), and B3LYP/6-31G(d) ab initio methods.     

Cross Aldolization Between Benzaldehyde and n-Heptaldehyde to α-Pentylcinnamaldehyde Overcalcined mg-al Hydrotalcites

Calcined Mg-Al hydrotalcites (CHT) with various Mg/Al atomic ratios were prepared and characterized by XRD, BET and TPD of carbon dioxide. The CHT catalysts were utilized for the synthesis of -pentylcinnamaldehyde (-P_c) from benzaldehyde and n-heptaldehyde in a stirred batch autoclave reactor. An increase of Mg/Al atomic ratio of CHT samples results in the apparent enhancement of catalyst basicity with concomitant decrease of surface areas. Both the catalytic activity and the -P_c selectivity increase with the catalyst basicity and the reaction temperature.     

Prins-Reaktionen mit Arylaldehyden, 5. Mitt.: Zur Umsetzung mit 2-Buten und mit Cyclohexen

By reaction of 2-[(1RS, 2RS)-2-hydroxy-1-methyl-propyl]-2-phenyl-1,3-dithiane (1 a) withcis-2-butene oxide, subsequent reduction and acetalizationc-4,t-5-dimethyl-r-2,c-6-diphenyl-1,3-dioxane (3 a) andt-4,c-5-dimethyl-r-2,c-6-diphenyl-1,3-dioxane (3 b) were synthesized as model compounds. For the same purpose by aldol reaction of cyclohexanone and reduction (1RS, 2SR)-2[(RS)-hydroxy-(4-methoxyphenyl)methyl]cyclohexanol (7 a), (1RS, 2RS)-2[(SR)-hydroxy-(4-methoxyphenyl)methyl]cyclohexanol (8 a), and (1RS, 2RS)-2[(RS)-hydroxy-(4-nitrophenyl)methyl]cyclohexanol (8 b) and by acetalization (2 , 4 , 4 a, 8 a)-2,4-bis(4-methoxyphenyl)hexahydro-4H-1,3-benzodioxin (9 a) and (2 , 4 , 4 a, 8 a)-2,4-bis(4-nitrophenyl)hexahydro-4H-1,3-benzodioxin (10 b) were obtained. FromPrins reactions, starting with 2-butene3 a,c-4,c-5-dimethyl-r-2,c-6-diphenyl-1,3-dioxane (3 c),r-4,t-5-dimethyl-c-6-phenyl-1,3,2-dioxathiane-2,2-dioxide (4), and (2Z, 4E)-1,5-diphenyl-4-methyl-2,4-pentadien-1-on (5), and starting with cyclohexene (E)-3-(4-methoxybenzylidene)cyclohexenyl-4-methoxyphenyl ketone (11) have been isolated in low yields.

4. Mitt.:Griengl, H., Nowak, P., Mh. Chem.109, 11 (1978).     

Development of an optical membrane for humidity

4-(N,N-dioctylamino)-4-trifluoroacetyl-azobenzene (ETH^T 4001), together with the catalyst tridodecylmethylammonium chloride, is dissolved in the hydrophilic polymer polyurethane Tecoflex. The resulting membrane layers show high sensitivity toward water vapour and allow the application of the membranes for humidity measurements. Upon exposure to humid air, the membrane exhibits a decrease in absorbance at a wavelength around 490 nm and an increase at around 430 nm. This signal change is caused by the conversion of the trifluoroacetyl group of the reactand into a diol, thus changing the electron delocalisation of the reactand. The sensor layer exhibits a dynamic range from 1% to 100% RH with highest sensitivity in the 5%–40% RH range. The limit of detection is 0.5% RH. The amount of added catalyst enables the sensitive range to be tailored. The selectivity over ethanol and carbonate is sufficient for the membrane to be used for long-term measurements of air. The change in colour of the humidity-sensitive membrane from red to yellow also means it can be used as an optical test strip.     

Synthesis ofS-(+)-hydroprene

A novel path toS-(+)-hydroprene (1) starting from the technical gradeS-(+)-dihydromyrcene (2, e.e. 50%) is proposed. The latter was selectively transformed intoS-3,7-dimethyloctanal (5) in three steps including hydroalumination. The reactions of5 with allyl- or methallylmagnesium chloride followed, respectively, either by oxygenation in the presence of PdCl₂/CuCl or by ozonolysis, affordS,E-6,10-dimethyl-3-undecen-2-one (7) which was treated with ethoxyethynylmagnesium bromide to give the title juvenile hormone analogue in 23% overall yield.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No 1, pp. 110–112, January, 1993.     

The properties of supported rhenium catalysts in the dehydrogenation of cyclohexane

The 2 % Re/sibunite catalyst is more active than 2 % Re/-Al₂O₃ and 2 % Re/-Al₂O₃ catalysts in the dehydrogenation of cyclohexane into benzene (T = 350 °C,w = 0.5 h–1). The substitution of NH₄ReO₄ by HReO₄ in the preparation of the catalyst enhances its activity by a factor of 1.3. Treatment with HNO₃ or oxalic acid increases the selectivity by a factor of 1.2 and 1.35, respectively, the overall conversion of cyclohexane being 32–40 %.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2119–2121, August, 1996.     

A new strategy for alkane oxidation with O2 using N‐hydroxyphthalimide (NHPI) as a radical catalyst

A practical catalytic method to convert alkanes into the corresponding oxygencontaining compounds with O₂ under mild conditions using Nhydroxyphthalimide (NHPI) in the presence or absence of a transition metal was developed. Thus, cyclohexane was successfully converted into adipic acid in good conversion and selectivity by a combined catalytic system consisting of NHPI and Mn(acac)₂. Lower alkane such as isobutane was converted into tbutyl alcohol (83%) under 10 atm of air by NHPICo(OAc)₂ system. Alkylbenzene such as toluene was oxidized to benzoic acid in high yield (81%) under normal temperature and pressure of dioxygen in the presence of a catalytic amount of NHPI and Co(OAc)₂. ESR measurements showed that phthalimideNoxyl generated from NHPI under dioxygen atmosphere is a key species in this oxidation and functions as a radical catalyst.