Search results for "Hydrogen"
showing 10 items of 4254 documents
Quantum-chemistry calculations of surface complex and orbital control in para/ortho toluene alkylation catalyzed by big pore zeolites
1994
Summary By means of MNDO-PM3 semiempirical quantum-chemistry calculations, the mechanism for alkylation of toluene by methanol on two zeolite clusters with Al and Ga as T III has been studied. The process variables controlled through the hypersurface of the reaction were: the distances of methyl group to the cluster of zeolite and to the toluene molecule; and the distances of the hydrogen atom of the toluene to be transfered to the zeolite cluster and to the toluene. The energetic factor associated with the electronic interaction between the molecular orbitals (LUMO of the zeolite-methoxy and HOMO of toluene) have been calculated by a PMO analysis for two geometries: the transition state an…
Pyrrole Studies. Part 40.1Synthesis of 2- and 3-Substitoted 1-Methylindoles from Vinylpyrroles.
1988
Abstract 4-Substituted-2-vinylpyrroles are more reactive than 2-substituted-4-vinylpyrroles in their reaction with DMAD to yield, respectively, 6/7- and 4,5-dihydroindoles, which are readily dehydrogenated to give indoles possessing electron-withdrawing substitutents at the 3- and 2-positions.
Synthesis and characterization of a new Organic – Inorganic sulfate (C5H6N2O)2[Co(H2O)6]3(SO4)4.2H2O
2014
crystals of a new hybrid compound, (C 5 H 6 N 2 O) 2 [Co(H 2 O) 6 ] 3 (SO 4 ) 4 .2H 2 O, were synthesized in aqueous solution and characterized. This compound crystallizes in the triclinic system with the space group P-1, the unit cell :a=6.632(3) A, b=11.769(5) A, c=14.210(6) A, α=67.86(4)°, β=81.32(4)°, γ=85.18(4)° and V=1015.14(8) A 3 . Its crystal structure can be described as a packing of alternated inorganic and organic layers. The different components are connected by a three-dimensional network of O-H…O and N-H…O hydrogen bonds.
Crystal Structures and Thermal Behavior of Bis(dibenzyldimethylammonium) Tetrabromometallates(II) [M = Mn(II), Co(II) and Zn(II)] and Their Solvates
2007
Six new A2MBr4 structures [A = dibenzyldimethylammonium cation,M = Mn(II), Co(II) or Zn(II)] were crystallized with or without solvent molecules from acetonitrile, methanol and/or aqueous solutions. The isomorphous compounds [(Bz2Me2N)2][MnBr4]·CH3CN·H2O (1) and [(Bz2Me2N)2]-[ZnBr4]·CH3CN·H2O (4) crystallize in the triclinic space group P1̄ from acetonitrile solutions. The solvent molecules participate in the hydrogen bonding network inside the crystal structure. [(Bz2Me2N)2][CoBr4]·0.5CH3CN (2) crystallizes from an acetonitrile solution in the monoclinic space group P21/c. The solvent molecules fill the voids of the crystal structure. Compound 2 is isostructural with the previously reporte…
1-Nitroindoline.
2000
In the title compound, C(8)H(8)N(2)O(2), the nitramino group is planar and only slightly twisted with respect to the indoline rings. The bridgehead N--C bond is slightly shorter than in typical secondary aromatic nitramines. The N--N bond has some double-bond character. The molecules are connected by weak C--H...O hydrogen bonds, forming chains parallel to the z direction.
Tetrakis(tert-butylammonium) benzene-1,2,4,5-tetracarboxylate octahydrate
2007
In the crystal structure of the title compound, 4C4H12N+·C10H2O8 4−·8H2O, there is a centre of symmetry at the centre of the benzene ring; the asymmetric unit comprises one half-anion, two cations and four water molecules. The pyromellitate tetraanion is nonplanar; it and the cations exhibit normal geometry. The two unique carboxylate groups are twisted out of the plane of the benzene ring by about 40 and 50°. The network formed by the ions and water molecules is based on eight O—H...O and six N—H...O strong hydrogen bonds.
A macrocyclic diurea derived from diphenylether
2010
Abstract A new 16-membered cyclic diurea was synthesized and tested as potential receptor for fluoride. 1 H and 19 F NMR spectroscopy revealed an unexpected deprotonation of both urea groups after initial 1:1 binding. A single crystal X-ray structure shows bifurcated hydrogen bonds to two DMSO molecules.
(1Z,3Z)-1,4-Di(pyridin-2-yl)buta-1,3-diene-2,3-diol: The Planar Highly Conjugated Symmetrical Enediol with Multiple Intramolecular Hydrogen Bonds
2002
1H, (13)C, and (15)N NMR spectral data show that in chloroform solution (1Z,3Z)-1,4-di(pyridin-2-yl)buta-1,3-diene-2,3-diol, OO, is in ca. 9:1 equilibrium with (3Z)-3-hydroxy-1,4-di(pyridin-2-yl)but-3-en-2-one, OK, while no 1,4-di(pyridin-2-yl)-2,3-butanedione, KK, was detected. The species present in the tautomeric mixture were identified by comparing their experimental chemical shifts with those known for similar compounds as well as with the theoretically calculated (GIAO-HF/DFT) values. Ab initio calculations show that OK and especially the highly conjugated OO forms are preferred in the tautomeric mixtures both in vacuo and in chloroform solution. Comparison of experimental (Arrhenius)…
Spin-Transition in [Fe(II)(2,6-Bis-(Benzimidazol-2′-yl)pyridine)2] (CIO4)2: Hysteresis Effect Dependent on the Matrix
1999
Abstract Far-Infrared spectroscopical investigation of the spin-crossover in [Fe(II)(2,6-bis-(benzimidazol-2′-yl)-pyridine)2] (CIO4)2 exhibits a hysteresis in both CsI and polyethylene matrices within temperature cycles between 100K and 520K. The hysteresis broadening is dependent on the matrix and bigger in CsI. This can be explained due to polarity and hydrogen bonding. Two low spin vibrations, LS1 at 437 cm−1 and LS2 at 424cm−1, are observed. On heating from 100K to 520K: during LS1 decreases, the LS2 raises temporarily, until both LS1 and LS2 disappear; for the HS only one raising species was observed. This gives raise to assume two different sub-lattices.
ChemInform Abstract: Synthesis and Electrode Reactions of Difluorogermanium(IV) Porphyrins. Molecular Stereochemistry and Crystal Structure of Difluo…
1988
The difluorogermanium(IV) porphyrins [GeF2(P)][P = 2,3,7,8,12,13,17,18-octaethylporphyrinate(2–)(oep), 5,10,15,20-tetraphenylporphyrinate(2–)(tpp), or 5,10,15,20-tetra-p-tolylporphyrinate(2–)(tptp)] have been prepared by reacting hydrogen fluoride with the appropriate dichloro derivative [GeCl2(P)]. The complexes were characterized by elemental analysis, 1H n.m.r., i.r., and u.v.–visible spectroscopy. The electrochemical behaviour was investigated in non-aqueous media while spectroelectrochemistry and e.s.r. were used to characterize the oxidized and reduced complexes. Each complex could be reversibly oxidized or reduced by one electron. In each case these electron additions or abstractions…