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.     

DSC study of the kinetics of the thermal dehydration of BaCl2 · 2H2O and BaCl2 · H2O

The kinetics of the thermal dehydration of various kinds of BaCl₂ · 2H₂O and of BaCl₂ · H₂O are investigated using a differential scanning calorimeter. The loss of H₂O proceeds in two steps: BaCl₂ · 2H₂O→BaCl₂ · H₂O→BaCl₂ and is therefore revealed by two endothermic peaks. In the experiments at varying temperature both steps follow a contracting-circle law, after an initial acceleratory stage according to a (n=2) power law. In the experiments at constant temperature, after an initial acceleratory stage according to a (n=2) power law, both steps (except BaCl₂ · 2H₂O single-crystals which follow a contracting-circle law) follow an Avrami-Erofeev law (withn=2) in the form used by Galwey and Jacobs. The activation energies for the various steps are compared and the different kinetic behaviour is discussed.     

Sc2MgGa2 and Y2MgGa2

Scandium magnesium gallide, Sc₂MgGa₂, and yttrium magnesium gallide, Y₂MgGa₂, were synthesized from the corresponding elements by heating under an argon atmosphere in an induction furnace. These intermetallic compounds crystallize in the tetragonal Mo₂FeB₂‐type structure. All three crystallographically unique atoms occupy special positions and the site symmetries of (Sc/Y, Ga) and Mg are m2m and 4/m, respectively. The coordinations around Sc/Y, Mg and Ga are pentagonal (Sc/Y), tetragonal (Mg) and triangular (Ga) prisms, with four (Mg) or three (Ga) additional capping atoms leading to the coordination numbers [10], [8+4] and [6+3], respectively. The crystal structure of Sc₂MgGa₂ was determined from single‐crystal diffraction intensities and the isostructural Y₂MgGa₂ was identified from powder diffraction data.     

Electrochemical study of (NEt4)2Cl2FeS2MoS2 and (NEt4)2Cl2FeS2MoS2FeCl2

Summary The ability of [MoS₄]^2–, anions to be used as ligands for transition metal ions has been widely demonstrated, especially with Fe²⁺. The present study has been restricted to linear complexes such as (NEt₄)₂ [Cl₂FeS₂MoS₂] and (NEt₄)₂[Cl₂FeS₂MoS₂FeCl₂]. Their electrochemical properties are described: upon electrochemical reduction, these compounds yield MoS₂, as a black precipitate, and an iron complex in solution, assumed to be [SFeCl₂]^2–. The electrochemical reduction goes through two electron transfers, coupled with the breakdown of the molecular skeleton: a DISPl and an ECE mechanism. Depending on the solvent, the following equilibrium may be observed: [Cl₄Fe₂MoS₄]^2–[Cl₂FeMoS₄]^2–+FeCl₂. The equilibrium constant, K_D, was evaluated by differential pulse polarography. K_D is tightly related to the donor number of the solvent.     

Rhodium catalysed [2+2+2] cycloadditions of acetylenes

Wilkinson's catalyst RhCl(PPh₃)₃ is an effective catalyst (0.5 – 2 mole %) for the rapid intermolecular trimerisation of 1,6-heptadiynes with monoacetylenes under mild conditions.     

Solid-phase hydrohalogenation of 2-methyl-2-butene

Complex formation between 2-methyl-2-butene and hydrogen halides (HX, X=Cl, Br) and the hydrohalogenation reaction was studied in the solid phase in the range of 80–150°K by IR spectroscopy. It was shown that 2-methyl-2-butene forms 11 and 12 complexes with HX. The hydrohalogenation reaction is realized by rearrangement of the 12 complex into a complex of the hydrohalogenation product with HX. The kinetics of the transformation depend on the ratio of the reagents. With an excess of the olefin the reaction is described by a kinetic equation of first order with respect to the complex of the initial reagents up to 60–80% conversion; with an excess of HX it is described by an equation of polychronous kinetics. The effective activation energy of the solid-phase halogenation of 2-methyl-2-butene is not greater than 20 kJ/mole. A molecular mechanism of addition to olefins in the solid phase is examined.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 1, pp. 34–40, January–February, 1987.     

Reactions of thiolate anions with 2-substituted-2-nitropropanes

Thiolates undergo substitution reactions with 2-substituted-2-nitropropanes by an S_RN1 mechanism or are oxidised to disulphides by an ionic mechanism.     

C-PhosphorylatedN 2-2-thiazolylformamidines

C-Phosphorylation of 2-thiazolylformamidines by phosphorus tribromide was studied. It was shown that the 1,3-diazabut-1-enyl (formamidine) substituent can be used as both an activating and protective group. 5-Phosphorylated thiazoles containing either a formamidine fragment or an amino group were obtained. Some properties of the compounds synthesized were studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1353–1359, July, 1999.     

Gas-Phase Molecular Structure of 2-Halo-1,3-dihetero-2-phospholanes

The molecular structure of 2-chloro-1,3-dithia-2-phospholane was determined using gas-phase electron diffraction and ab initio calculations. The heteroring in the molecule has an asymmetric structure like a symmetric P-envelope twisted about the C-C bond with an axial P-Cl bond. Geometric parameters of the molecule and mean vibration amplitudes were determined. The molecular structure of 2-chloro-1,3-oxathia-2-phospholane was predicted. The molecule in the gas phase has two conformers [twisted C(O)- and C(S)-envelope] with an axial P-Cl bond.     

Kinetics of epoxidation of 2-methyl-2-pentene

The kinetics of epoxidation of 2-methyl-2-pentene with cumene hydroperoxide catalyzed by MoO₂ (acac)₂ has been studied in the temperature range of 35–65°C. The observed kinetic behavior is consistent with the formation of a hydroperoxide-catalyst complex and a simple competitive inhibition step, involving the formation of an inactive epoxide-catalyst complex. The reaction parameters have been calculated.     

Syntheses,Crystal Structure,and Properties of Hf2Ni2In,Hf2Ni2Sn,Hf2Cu2In,and Hf2Pd2In with Ordered Zr3Al2 Type Structure

Hf₂Ni₂In, Hf₂Ni₂Sn, Hf₂Cu₂In, and Hf₂Pd₂In were synthesized by reacting the elements in an arc-melting furnace under argon and subsequent annealing at 970 K. They crystallize with an ordered Zr₃Al₂ type structure, space group P4₂/mnm which was refined from single crystal X-ray data for Hf₂Ni₂In (a = 713.9(1) pm, c = 660.4(2) pm, wR2 = 0.0665, 513 F² values) and Hf₂Ni₂Sn (a = 703.1(1) pm, c = 676.1(2) pm, wR2 = 0.0423, 507 F² values) with 18 parameters for each refinement. The lattice constants for Hf₂Cu₂In and Hf₂Pd₂In are a = 715.5(1) pm, c = 677.0(1) pm and a = 742.6(1) pm, c = 679.4(2) pm, respectively. The structures may be considered as an intergrowth of distorted CsCl- and AlB₂-like slabs. Magnetic susceptibility measurements indicate Pauli paramagnetism for Hf₂Ni₂In and Hf₂Ni₂Sn, which is consistent with the metallic conductivity observed for Hf₂Ni₂In. ¹¹⁹Sn Mössbauer spectroscopy of Hf₂Ni₂Sn shows one signal with an isomer shift of δ = 1.59(1) mm/s subjected to quadrupole splitting of δE_q = 0.81(1) mm/s.     

Electronic structure and one-electron properties of the MoO2Cl2 molecule. Electronic spectra of the MoO2Cl2, MoO2Br2 and WO2Br2 molecules

The SCF-X -SW method in an overlapping atomic spheres approximation has been used to calculate the electronic structure, ionization potentials, energies and oscillator strengths of the allowed optical transitions and also some of the one-electron properties of the MoO₂Cl₂ molecule. The electronic absorption spectra of vapours over molybdenum and tungsten dioxodibromides have been measured. Interpretation of the experimental electronic absorption spectra of the MoO₂Cl₂, MoO₂Br₂ and WO₂Br₂ molecules is discussed.     

Crystal Structure of Guanylurea Sulphate Hydrate [H2NC(=O)NHC(NH2)2]2SO4 · 2 H2O

Single crystals of guanylurea (1–carbamoylguanidinium) sulphate hydrate (C 2/c, a = 30.353(6), b = 6.6162(13), c = 21.204(4) Å, β = 99.37(3)°, V = 4201.4(14) ų, T = 200 K) were obtained from a neutral aqueous solution containing guanylurea sulphate. By analogy with previously reported simple molecular guanylurea salts, the title compound builds up an array of mutually linked chains of cations and anions, with the crystal packing being largely controlled by an extensive hydrogen bonding network.     

Relativistic bond lengthening of UO 2 2+ and UO2

Summary Relativistic calculations on UO₂ [1] have shown that relativity leads to substantial bondlengthening in this compound, in contrast to the bond contraction found almost exclusively for other compounds. The bond lengthening isnot caused by the relativistic expansion of the 5f valence AO of U, which is the primary bond forming orbital on U in UO₂. The origin of the bond lengthening can be traced back to the semi-core resp. subvalence character of the U 6p AO. The valence character of 6p shows up in an increasing depopulation of the 6p upon bond shortening, and hence loss of mass-velocity stabilization. The core character of 6p shows up in large off-diagonal mass-velocity matrix elements 5p|h _MV|6p which are shown to have an overall bond lengthening effect. The larger expansion in UO₂ than in UO ₂ ²⁺ is due to destabilization of U levels in UO₂, caused by repulsion of the two additional 5f electrons.The present analysis corroborates the picture of relativistic bond length effects of Ref. [2].     

The pentacoordinate titanium complex [TiCl2(NMe2)2(HNMe2)]

Amido complexes of titanium are useful reagents in a variety of syntheses and as precursors for chemical vapour deposition of TiN. The title compound, di­chloro­bis­(di­methyl­amido)(di­methyl­amine)­titanium(IV), [TiCl₂(C₂H₆N)₂(C₂H₇N)], crystallizes with one mol­ecule in the asymmetric unit. The neutral complex shows an unusual fivefold coordination of the titanium centre with a distorted trigonal–bipyramidal geometry and the di­methyl­amine mol­ecule occupying an axial position.     

Covalent Patterning of 2D MoS2

The development of an efficient method to patterning 2D MoS₂ into a desired topographic structure is of particular importance to bridge the way towards the ultimate device. Herein, we demonstrate a patterning strategy by combining the electron beam lithography with the surface covalent functionalization. This strategy allows us to generate delicate MoS₂ ribbon patterns with a minimum feature size of 2 μm in a high throughput rate. The patterned monolayer MoS₂ domain consists of a spatially well-defined heterophase homojunction and alternately distributed surface characteristics, which holds great interest for further exploration of MoS₂ based devices.     

Mechanism of dehydration of 2-CH2R-and 2-CHR2-4-hydroxy-Δ2-thiazolines as intermediates in the Hantzsch thiazole synthesis and factors impeding the synthesis of 2-Me-, 2-Ar-, and 2-Het-substituted thiazoles and thiazolo[5,4-b]indoles

Based on the results of studies of the deuterium exchange and dehydration of 4-hydroxy-Δ²-thiazolines and 2-R-4-acetyl-8b-hydroxy-3a,8b-dihydro-4H-thiazolo[5,4-b]indoles containing the α-methylene (methine) unit at the C(2) atom, the mechanism of dehydration of these compounds generated as intermediates in the Hantzsch synthesis of thiazoles and 2-R-4-acetyl-4H-thiazolo[5,4-b]indoles was proposed. This mechanism includes an additional step of the formation of the corresponding Δ³-thiazolines. According to the results of quantum chemical calculations, this is energetically more favorable than the dehydration in terms of the commonly accepted mechanism. In some cases, an acidic medium impedes the dehydration of 4-hydroxy-Δ²-thiazolines or their cyclic analogs. The proposed mechanism provides an explanation for the empirical data on the differences in the reactivities of both thioamides and α-haloketones, which have remained unexplained in terms of the commonly accepted mechanism. The spontaneous thiazole synthesis is virtually impossible starting from thioamides of aromatic or heteroaromatic acids and α-haloketones bearing electron-withdrawing α′ substituents or cyclic bromoindoxyl-type haloketones. In the thiazole synthesis from these starting components, it is expedient to perform dehydration under basic catalysis. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1394–1402, July, 2007.     

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.     

Electrochemically initiated intramolecular cyclization of 2-nitro-2′-isothiocyanatobiphenyl

2-Nitro-2′-isothiocyanatobiphenyl was prepared as a new substance, suitable for the investigation of an electrochemically initiated intramolecular cyclization. If it is reduced at a mercury cathode in acidic media an acid catalysed intramolecular follow-up reaction occurs which leads to the formation of 6-mercaptodibenzo (d, f)-(1,3)-diazepin-5-oxide. The rate of the follow-up reaction decreases in neutral or alkaline media and the reduction of the isothiocyanato group also takes place. The main product is here 5,6-dihydrobenzo(c)cinnoline.     

A General Synthesis of 2-Methoxy-2-Cyclohexenones

The preparation of octalinone 1 at an early stage of a recent synthesis of valeranone¹ required the use of a Robinson annelation with 1,4-dimethoxy-2-butanone (2a), a methoxymethyl vinyl ketone (3) equivalent. The following syntheses of 2-methoxy-2-cyclohexenones illustrate further examples of the heretofore unexploited reaction.²