Experimental determination of the rate constants of the reactions of HO2 + DO2 and DO2 + DO2

The rate constants of the reactions of DO₂ + HO₂ (R1) and DO₂ + DO₂ (R2) have been determined by the simultaneous, selective, and quantitative measurement of HO₂ and DO₂ by continuous wave cavity ring-down spectroscopy (cw-CRDS) in the near infrared, coupled to a radical generation by laser photolysis. HO₂ was generated by photolyzing Cl₂ in the presence of CH₃OH and O₂. Low concentrations of DO₂ were generated simultaneously by adding low concentrations of D₂O to the reaction mixture, leading through isotopic exchange on tubing and reactor walls to formation of low concentrations of CH₃OD and thus formation of DO₂. Excess DO₂ was generated by photolyzing Cl₂ in the presence of CD₃OD and O₂, small concentrations of HO₂ were always generated simultaneously by isotopic exchange between CD₃OD and residual H₂O. The rate constant k₁ at 295 K was found to be pressure independent in the range 25–200 Torr helium, but increased with increasing D₂O concentration k₁ = (1.67 ± 0.03) × 10⁻¹² × (1 + (8.2 ± 1.6) × 10⁻¹⁸ cm³ × [D₂O] cm⁻³) cm³ s⁻¹. The rate constant for the DO₂ self-reaction k₂ has been measured under excess DO₂ concentration, and the DO₂ concentration has been determined by fitting the HO₂ decays, now governed by their reaction with DO₂, to the rate constant k₁. A rate constant with insignificant pressure dependence was found: k₂ = (4.1 ± 0.6) × 10⁻¹³ (1 + (2 ± 2) × 10⁻²⁰ cm³ × [He] cm⁻³) cm³ s⁻¹ as well as an increase of k₂ with increasing D₂O concentration was observed: k₂ = (4.14 ± 0.02) × 10⁻¹³ × (1 + (6.5 ± 1.3) × 10⁻¹⁸ cm³ × [D₂O] cm⁻³) cm³ s⁻¹. The result for k₂ is in excellent agreement with literature values, whereas this is the first determination of k₁.     

Enthalpies of combustion and formation of 2-acetylpyrrole, 2-acetylfuran and 2-acetylthiophene

The combustion energies for 2-acetylpyrrole (cr) and 2-acetylfuran (cr) were determined using a static bomb calorimeter, whereas the combustion energy of 2-acetylthiophene (l) was determined with a rotating bomb calorimeter; both calorimeters have been recently described. The molar combustion energies obtained were: −(3196.1 ± 0.6) kJ mol⁻¹ for 2-acetylpyrrole, −(2933.8 ± 0.7) kJ mol⁻¹ for 2-acetylfuran, and −(3690.4 ± 0.8) kJ mol⁻¹ for 2-acetylthiophene. From these combustion energy values, the standard molar enthalpies of formation in the condensate phase were obtained as: −(163.51 ± 0.97) kJ mol⁻¹, −(283.50 ± 1.06) kJ mol⁻¹ and −(123.93 ± 1.15) kJ mol⁻¹, respectively. The obtained values of combustion and formation enthalpies of 2-acetylthiophene are in concordance with the reported previously. For the two last compounds, polyethene bags were used as an auxiliary material in the combustion experiments. The heat capacities and purities of the compounds were determined using a differential scanning calorimeter.     

Microwave-assisted synthesis of 2-aminonicotinic acids by reacting 2-chloronicotinic acid with amines

2-(Methylamino)nicotinic acid was readily prepared in high yield by reacting 2-chloronicotinic acid with 40% aq MeNH₂ under microwave irradiation either at 120 °C for 2 h or at 140 °C for 1.5 h. Subsequently, we found that a range of 2-aminonicotinic acids could be obtained under microwave heating. The optimal reaction conditions involved the use of 3 equiv of amine, water as the solvent and heating at 200 °C for 2 h in the presence of diisopropylethylamine (3 equiv).     

Crystallization Behavior of SiO2-TiO2 Ceramics Derived from Titanosiloxanes on Pyrolysis

The crystallization behavior of SiO2-TiO2 ceramics derived from titanosiloxanes was investigated in relation to the structure of the precursor and the pyrolysis temperature. The titanosiloxanes, [Si(OBut)2OTi(acac) 2O]2, [(ButO)3SiO] 2Ti (OPri)2, and [(ButO)3SiO] 3Ti(OPri), were pyrolyzed in an air atmosphere to form SiO2-TiO2 ceramics which crystallized to anatase at 600–650°C, 700–750°C, and 800–850°C, respectively. The crystallization temperature decreased with increased titanium content of the precursor. The average crystallite size of anatase increased with increased pyrolysis temperature and the titanium content. The crystallization temperature and the crystallite size for SiO2-TiO2 ceramics is controlled by the precursor structure, which may enable control of the physical properties of the ceramic materials.     

Application of ZrO2-Al2O3 Aerogels to Catalysts

ZrO2-Al2O3 aerogels were prepared by hydrolysis of metal alkoxides in alcoholic solutions and supercritical drying in order to obtain an improved de-NOx catalyst with high activity in a wide temperature range. The aerogels have about 20–50% higher activity than the xerogels in the range 300–600°C. The higher activity of aerogels may be attributed to the higher effective gas diffusivity in them, estimated to be about 20–60 times higher than that of the xerogels, because of their high porosity and large pore size. The catalytic activity of aerogels containing 4–10 mol% ZrO2 is more than 20% higher than that of Al2O3 aerogels at temperatures <450°C.     

A novel way to chiral 2-oxazolidinones: selenium-catalyzed cyclocarbonylation of 2-aminoethanols

Selenium-catalyzed cyclocarbonylation of 2-aminoethanols with CO under atmospheric pressure at 30 °C afforded 2-oxazolidinones in excellent yields without any other co-catalyst. The method was then applied to the syntheses of chiral 2-oxazolidinones and no racemization was detected.     

Hydrolysis of 2-alkoxyalk-2-enals

Hydrolysis of 2-alkoxyalk-2-enals with equimolar amount of water (in an organic solvent) and with an excess of water has been studied with the aim of synthesizing 2-oxopropanal (methylglyoxal). 2-Oxopropanal obtained in an excess of water exists in the hydrate from. In organic solvents, the cyclic trimer of 2-oxopropanal, 2,4,6-triacetyl-1,3,5-trioxane, predominates (NMR data). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2547–2549, December, 1998.     

The reaction of MgCl2·4H2O with CCl2F2

A new reaction of MgCl₂·4H₂O with CCl₂F₂ is investigated by DTA and TG from room temperature to 350 °C. It is observed that MgF₂ was obtained between 252 and 350 °C, Below the temperature, MgCl₂·4H₂O dehydrates and hydrolyzes to MgCl₂ and Mg(OH)Cl, which are the real reactants of the reaction with CCl₂F₂. The formation of MgF₂ is ascribed to the reaction of MgCl₂ and Mg(OH)Cl with HF, which forms by decomposition of CCl₂F₂ with the taking part in of H₂O released from dehydration of hydrated magnesium chloride on the surface of MgCl₂ and Mg(OH)Cl, which catalyzes the decomposition of CCl₂F₂ in this case. Consequently, the reactions are tested in the fluid-bed condition. It is found that MgF₂ formed at temperatures down to 200 °C in a fluid-bed reactor. This reaction may be used as a method of disposing of the environmentally sensitive CCl₂F₂ (rather than release into the atmosphere). It is also a method for the preparation of MgF₂.     

Concise syntheses of 2-aminoindans via indan-2-ol

2-Amino-5,6-dimethoxyindan hydrochloride was synthesized in seven steps and with an overall yield of 48%. Indan-2-ol was converted to 5,6-dibromo-indan-2-ol in three steps by acetylation, electrophilic bromination and deacetylation. Dimethoxylation of 5,6-dibromoindan-2-ol with NaOCH₃ in the presence of CuI gave 5,6-dimethoxy-indan-2-ol, which was converted to 2-amino-5,6-dimethoxyindan hydrochloride by azidation, followed by Pd-C catalyzed hydrogenation. Similarly, 2-amino-5-bromoindan was synthesized in five steps and with an overall yield of 50%. Indan-2-ol was converted to 2-aminoindan by azidation followed by Pd-C catalyzed hydrogenation. The reaction of 2-aminoindan with 2.5 equiv Br₂ afforded 2-amino-5,6-dibromoindan.     

Efficient synthesis of 2-imidazol-2-ylacetates

A simple method of synthesizing various 2-imidazol-2-ylacetates is described. Condensation of α-aminoketals with imidates, followed by cyclization in refluxing 4 M-HCl/Dioxane, yielded 2-imidazol-2-ylacetates under one-pot and mild reaction conditions.     

Analysis of 5-hydroxy-N-methyl-2-pyrrolidone and 2-hydroxy-N-methylsuccinimide in plasma

Summary A method for the determination of 5-hydroxy-N-methyl-2-pyrrolidone (5-HNMP) and 2-hydroxy-N-methylsuccinimide (2-HMSI) in plasma was developed. 5-HNMP and 2-HMSI are metabolites to the widely used organic solvent N-methyl-2pyrrolidone (NMP). The 5-HNMP and 2-HMSI were purified from plasma by C8 solid phase extraction, derivatised by bistrimethylsilyl trifluoroacetamid, and analysed by gas chromatography with mass spectrometric detection. For 5-HNMP, the precision was 2–7 % (120 and 780 ng mL⁻¹) and the detection limit was 6 ng mL⁻¹ (m/z 98). For 2-HMSI, the precision was 2–9 % (160 and 1000 ng mL⁻¹) and the detection limit was 4 ng mL⁻¹ (m/z 144). The method is applicable for analysis of plasma samples from workers exposed to NMP.     

A practical synthesis of 2′-aminoacylamino-2′-deoxyadenosines

A practical and efficient synthesis of 2′-aminoacylamino-2′-deoxyadenosine derivatives is reported. EDCI/HOBt-mediated coupling of a 3′,5′-diprotected 2′-amino-2′-deoxyadenosine derivative to various N-Cbz-l-amino acid derivatives followed by global deprotection affords analytically pure 2′-aminoacylamino-2′-deoxyadenosine derivatives without the necessity for preparative HPLC purification. These compounds are non-hydrolysable isosteres of 2′-aminoacyladenosines, which are of use in X-ray studies for the elucidation of the editing mechanism of various tRNA synthetases.     

Reactions of 1,3-dioxacycloalkanes and their 2-arsena, 2-bora, 2-germa, 2-sila,and 2-thia analogs with nitriles

New reactions of five-, six-, and seven-membered 1,3-dioxacycloalkanes and their 2-arsena, 2-bora, 2-germa, 2-sila, and 2-thia analogs with nitriles giving rise to 1,3-oxazacycloalkanes and then to amino alcohols are surveyed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1499–1507, July, 2005.     

Synthesis of 2-cyanoacrylatesvia 2-cyanoacryloyl chloride

Monomers that are difficult to obtain, such as tert-butyl 2-cyanoacrylate, trimethylsilyl-methyl 2-cyanoacrylate, 2,2,3,3-tetrafluoropropyl 2-cyanoacrylate, and the previously unknown adamantyl 2-cyanoacrylate were prepared starting from 2-cyanoacryloyl chloride.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1339–1340, July, 1994.     

Heterogeneous catalytic oxidation of chromotrope 2B with H2O2 and metal complexes supported on aluminum oxide hydroxide as catalyst

The heterogeneous catalytic oxidation of Chromotrope 2B (C2B) dye with H₂O₂ and the aluminum oxide hydroxide (AlOOH) modified with ammonia complexes of Cu^II, Co^II, Ni^II, and Cr^III (AlOOH/[Mⁿ⁺(amm)_m]) as catalysts were studied. The AlOOH/[Cu^II(amm)₄] is the most efficient catalyst and therefore it was chosen as the potential catalyst for the oxidative degradation of C2B in an aqueous solution. The AlOOH/[Cu^II(amm)₄] was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and transmission electron microscopy (TEM), techniques. The rate of reaction was dependent on the type of the metal complex supported on the AlOOH, initial concentration of the dye and H₂O₂, catalyst dose, pH, the concentration of NaCl, and temperature. The catalytic activity of the AlOOH/[Mⁿ⁺(amm)_m] according to the kind of metal ion decreased in the order: Cu^II > Co^II > Cr^III > Ni^II. Other catalysts consisting of the AlOOH supported with Cu^II complexed with ethylenediamine, ethanolamine, 1,3 propanediamine, and 1,4 butanediamine, (AlOOH/[Cu^II(amine)_m]), were also investigated. The activity of the (AlOOH/[Cu^II(amine)_m]) as catalyst according to the type of ligand followed the order: 1,4 butanediamine > 1,3 propanediamine > ethanolamine > ethylenediamine > ammonia. The reaction rate increased with increasing the catalyst dose, concentration of H₂O_2, C2B, and NaCl, pH, and temperature. Since the reusability results for the AlOOH/[Cu^II(amm)₄] revealed good stability over seven cycles, it can thus be considered a promising and cost-effective catalyst for the removal of harmful dyes from wastewater.     

New methods for the preparation of aryl 2-iminoimidazolidines

A divergent strategy for the synthesis of 1-aryl- and 2-aryl-2-iminoimidazolidines is presented. Cyclization of N-Boc-N′-aryl-N′′-(2-hydroxyethyl)guanidines in the presence of methanesulfonyl chloride and triethylamine or sodium hydride at 0 °C affords the corresponding 2-iminoimidazolidines in good yields.     

Frontier-orbital analyses of ketene [2+2] cycloadditions

Twelve kinds of ketene [2+2] cycloadditions have been investigated by ab initio calculations. They are composed of four ketenes (Y–HC=C=O, Y=H, NH₂, Cl, and CN) and three isoelectronic ketenophiles (ethylene, methylenimine, and formaldehyde). All the transition state geometries obtained here are not different significantly, but the extent of formation of two covalent bonds differs appreciably. The difference is attributable to the degree of the charge transfer interactions. One is the interaction from the π orbital and/or the lone pair orbital of a ketenophile to the LUMO of a ketene (dominant charge transfer, CT1). The other is that from the HOMO of the ketene to the π* orbital of the ketenophile (second dominant charge transfer, ct1). CT1 contributes to the formation of only one covalent bond, and ct1 does to the formation of the other. This independent function is characteristic of ketene [2+2] cycloadditions. They are not concerned with the orbital phase. We also have examined Fukui's postulate that the deformation of particular frontier orbitals causes the reaction progress. The role has been verified both by configuration analyses along the intrinsic reaction coordinate of the ketene-ethylene reaction and by the examination of distortions of frontier-orbital shapes along the low-frequency vibrational modes. Received: 25 June 1998 / Accepted: 28 August 1998 / Published online: 11 November 1998     

A stereocontrolled construction of 2-azido-2-deoxy-1,2-trans-β-glycosidic linkages utilizing 2-azido-2-deoxyglycopyranosyl diphenyl phosphates

A high-yielding and stereocontrolled construction of 2-azido-2-deoxy-1,2-trans-β-glycosidic linkages has been achieved by exploiting TMSOTf-promoted 1,2-trans-glycosidation of 2-azido-2-deoxyglycopyranosyl diphenyl phosphates with various glycoside alcohols in propionitrile at −78°C. The present method exhibits the highest levels of 1,2-trans-β-selectivity reported to date for this type of glycosidation.     

Solubility of carbon dioxide in aqueous solution of 2-amino-2-methyl-1-propanol and piperazine

In this work, new experimental results of the vapour-liquid equilibrium (VLE) of CO₂ in aqueous 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) have been presented in the temperature range of 298-328 K and PZ concentration range of 2-8 mass%, keeping the total amine concentration in the solution at 30 mass%. The partial pressures of CO₂ were in the range of 0.1-1450 kPa. A thermodynamic model was developed to correlate and predict the VLE of CO₂ in aqueous AMP + PZ. The electrolyte nonrandom two liquid (ENRTL) theory has been used to develop the VLE model for the quaternary system (CO₂ + AMP + PZ + H₂O) to describe the equilibrium behaviour of the solution. The experimental data from this work and data available in the literature were used to regress the ENRTL interaction parameters. The model predictions are in good agreement with the experimental data of CO₂ solubility in aqueous blends of this work as well as those reported in the literature. The current model can also predict speciation, heat of absorption, pH of the CO₂ loaded solution, and amine volatility.     

One-pot synthesis of 2-(2-hydroxyaryl)quinolines: reductive coupling reactions of 2′-hydroxy-2-nitrochalcones

A one-pot synthesis of novel 2-(2-hydroxyaryl)quinolines have been developed from the intramolecular reductive coupling reactions of 2′-hydroxy-2-nitrochalcones, induced by stannous chloride in acidic medium (HCl/AcOH). In some cases these transformations can be performed with ammonium formate/Pd-C in methanol.