Phase transformation and structure of n-C50H102/n-C60H122 solid solutions formed from the vapor phase

Binary solid solutions of n-paraffins (n-C₅₀H₁₀₂/n-C₆₀H₁₂₂) epitaxially prepared on potassium hydrogen phthalate substrate from the vapor phase have been studied by electron diffraction to characterize their phase transitions and structure. The continuity of solid solution in the n-C₅₀H₁₀₂/n-C₆₀H₁₂₂ system is demonstrated once lamellar ordering of the crystal packing is achieved. However, such ordering is achieved only by annealing and proceeds through a series of intermediate chain packings. At first, the electron diffraction patterns from all samples prepared at room temperature resemble those from polyethylene, in which no spots corresponding to the interlayer spacings appear. Longitudinal chain translations are induced by annealing to cause the lamellar reflections to appear, while the “polyethylene” subcell reflections remain unsplit until the crystal structure with well-defined methyl end planes is reached.     

Monte Carlo simulation for pVT relationship of CO2+n-C4H10 and CO2+i-C4H10 systems

Monte Carlo simulation has been applied to calculate the pVT relationship of CO₂+butane (n-C₄H₁₀ and i-C₄H₁₀) systems at 310.93 K and up to 9.5 MPa. CO₂ is treated as a single-site molecule and butanes are treated as four-site molecules. The Lennard–Jones (12–6) potential is used as the site–site potentials and the combining rules proposed by Jorgensen et al. [W.L. Jorgensen, J.D. Madura, C.J. Swenson, J. Am. Chem. Soc. 106 (1984) 6638.] are adopted for unlike site pairs. The calculated results of the pVT relationship show good agreement with the experimental data [T. Tsuji, S. Honda, T. Hiaki, M. Hongo, J. Supercrit. Fluids 13 (1998) 15.] by introducing an intersite interaction parameter between unlike molecules. Furthermore, the radial distribution functions and the number of CO₂ and butanes around butanes are calculated as a fundamental information on the microscopic structures. It is found that the radial distribution functions and the number of CO₂ and n-C₄H₁₀ around n-C₄H₁₀ are different from those of CO₂ and i-C₄H₁₀ around i-C₄H₁₀.     

Hydrotrope and hydrotrope-solubilization action of penicillin-K in CTAB/n-C5H11OH/H2O system

Penicillin potassium salt (penicillin-K) is found to show hydrotrope action, which can increase the solubility of cationic surfactant CTAB in water. Penicillin-K also shows hydrotrope-solubilization action, which makes the W/O and O/W microemulsion more stable and increases the solubilized amount of n-C₅H₁₁OH in O/W microemulsion and that of water in W/O microemulsion for CTAB/n-C₅H₁₁OH/H₂O system. However, in this system, the presence of penicillin-K can decrease the stability of the lamellar liquid crystal phase due to its structure change to bicontinuous, which are proved by the mechanism of its hydrotrope-solubilization action.     

Low-frequency intramolecular and lattice vibrations of n-C36H74 as studied by Raman scattering

The Raman spectrum of n-C₃₆H₇₄ has been measured in the region between 0 and 150 cm^?1. Eleven newly observed bands have been assigned to the intramolecular skeletal vibrations and rotatory lattice vibrations on the basis of the dispersion curves calculated previously.     

The release of cephanone in CTAB/n-C5H11OH/H2O system

Controlled release of cephanone from hexadecyltrimethylammonium bromide (CTAB) micelles and CTAB/n-C₅H₁₁OH/H₂O microemulsions was studied. The results showed that the release rate of cephanone was reduced in CTAB micelles and CTAB/n-C₅H₁₁OH/H₂O microemulsions, because of the solubilization of cephanone in micelles and microemulsions. The release of cephanone from CTAB micelles and CTAB/n-C₅H₁₁OH/H₂O microemulsions was characterized by Fickian diffusion and non-Fickian diffusion.     

(n-C5H5) (CO)2W{n3-C5H5[(n-C5H4)2Fe]} - ein neuer Fe und N enthaltender Zweikernkomplex

(η-C₅H₅)(CO)₂W[(η³-C₅H₅)(C₅H₅)₂], I, containing two tilted five-membered rings, is converted into the bridged ferrocene derivative (η-C₅H₅)(CO)₂W{(η³-C₅H₅)}[(η-C₅ H₄)₂Fe]} II by successive reaction with Na and FeCl₂.     

Low-frequency Raman-active vibrations of triclinic n-paraffins

The low-frequency Raman spectra of triclinic n-paraffins, n-C₈H₁₈ through n-C₂₄H₅₀, were observed. The normal-coordinate treatments of crystal vibrations of n-C₈H₁₈ through n-C₁₈H₃₈ were carried out. Six characteristic series of the observed Raman lines were assigned to rotatory lattice vibrations and intramolecular skeletal vibrations.     

Subsolidus phase diagram of the binary system (n-C n H2n+1NH3)2CoCl4

The perovskite-type layered compounds decylammonium tetrachlorocobaltate (n-C₁₀H₂₁NH₃)₂CoCl₄ and dodecylammonium tetrachlorocobaltate (n-C₁₂H₂₅NH₃)₂CoCl₄ exist the solid–solid phase transition in the temperatures range 330–380 K. These laminar materials contain bilayers sandwiched between metal halide layers. The experimental subsolidus binary phase diagram of (n-C₁₀H₂₁NH₃)₂CoCl₄–(n-C₁₂H₂₅NH₃)₂CoCl₄ has been established over the whole composition range by differential thermal analysis and X-ray diffraction. In the phase diagram, one intermediate compound (n-C₁₀H₂₁NH₃) (n-C₁₂H₂₅NH₃)CoCl₄ at $ W_{{{\text{C}}_{ 1 0} {\text{Co}}}} \% = 50. 9 2 $ and two eutectoid invariants points at $ W_{{{\text{C}}_{ 10} {\text{Co}}}} \% = 2 9. 8 3 $ and $ W_{{{\text{C}}_{ 10} {\text{Co}}}} \% = 7 7. 9 8 $ were observed, two eutectoids temperatures are about 343 ± 1 and 340 ± 1 K. There are three noticeable solid solution ranges (α, β, γ) at the left and right boundary and middle of the phase diagram.     

Isotropic C6, C8 and C10 interaction coefficients for CH4, C2H6, C3H8, n-C4H10 and cyclo-C3H6

The non-empirical generalized Kirkwood, Unsöld, and the single-Δ Unsöld methods (with double-zeta quality SCF wave-functions) are used to calculate isotropic dispersion (and induction) energy coefficients C_2n, with n ? 5, for interactions involving ground state CH₄, C₂H₆, C₃H₈, n-C₄H₁₀ and cyclo-C₃H₆. Results are also given for the related multipole polarizabilities α_l, multipole sums S₁/(0) and S₁(?1) which are evaluated using sum rules, and the permanent multipole moments. for l = 1 (dipole) to l = 3 (octupole). Estimates of the reliability of the non-empirical methods, for the type of molecules considered, are obtained by a comparison with accurate literature values of α₁S₁(?1) and C₆. This, and the asymptotic properties of the multipolar expansion of the dispersion energy, the use to discuss recommended representation for the isotropic long range interaction energies through R^?10 where R is the intermolecular separation.     

Rotational isomerism in alkylgermane molecules (Alk = Bun,n-C6H13) according to Raman spectroscopy and quantum-chemistry results

Temperature study of Raman spectra of alkylgermanes (Alk = Buⁿ, n-C₆H₁₃) in liquid, polycrystalline, and glassy states was carried out. The spectra of liquid samples are complicated, because compounds exist as equilibrium mixtures of rotational isomers due to hindered rotation about C—C and Ge—C bonds. In crystals, only the most stable conformer persists, which results in simplification of the spectrum. Unlike n-hexylgermanes, n-butylgermanes crystallize on cooling with difficulties. Quantum-chemical calculations of the geometry and normal coordinate analysis of the possible conformers of the BuⁿGeH₃, BuⁿGeCl₃, and Buⁿ ₂GeCl₂ molecules were performed. The unusually large (65 cm^–1) difference between the experimental (Ge—C) stretching frequencies of the trans and gauche conformers about the C—C bond nearest to the Ge atom is attributed to the difference in the electronic structure of these conformers, which is manifested in the differences in the Ge—C bond lengths, molecular geometry, and their force fields and, consequently, affects the mode frequencies and eigenvectors.     

Temperature-dependent kinetics studies of the reactions of C2H5O2 and n-C3H7O2 radicals with NO

The rate coefficients for the gas-phase reactions of C₂H₅O₂ and n-C₃H₇O₂ radicals with NO have been measured over the temperature range of (201–403) K using chemical ionization mass spectrometric detection of the peroxy radical. The alkyl peroxy radicals were generated by reacting alkyl radicals with O₂, where the alkyl radicals were produced through the pyrolysis of a larger alkyl nitrite. In some cases C₂H₅ radicals were generated through the dissociation of iodoethane in a low-power radio frequency discharge. The discharge source was also tested for the i-C₃H₇O₂ + NO reaction, yielding k_{298 K} = (9.1 ± 1.5) × 10⁻¹² cm³ molecule⁻¹ s⁻¹, in excellent agreement with our previous determination. The temperature dependent rate coefficients were found to be k(T) = (2.6 ± 0.4) × 10⁻¹² exp{(380 ± 70)/T} cm³ molecule⁻¹ s⁻¹ and k(T) = (2.9 ± 0.5) × 10⁻¹² exp{(350 ± 60)/T} cm³ molecule⁻¹ s⁻¹ for the reactions of C₂H₅O₂ and n-C₃H₇O₂ radicals with NO, respectively. The rate coefficients at 298 K derived from these Arrhenius expressions are k = (9.3 ± 1.6) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ for C₂H₅O₂ radicals and k = (9.4 ± 1.6) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ for n-C₃H₇O₂ radicals. © 1996 John Wiley & Sons, Inc.     

The transition metal catalysed reaction between η5-C5H5Mo(CO)3I and isonitriles

The reaction betweeen (η⁵-C₅H₅Mo(CO)₃I and RNC is catalysed by [η⁵ -C₅H₅Mo(CO)₃]₂ and readily yields η⁵-C₅H₅Mo(CO)_3?n(RNC)_nI (n = 1–3). A free radical mechanism is consistent with experimental data.     

Vibrational analysis of 1-iodopropane-D7 and 1-iodobutane-D9: A force field for primary iodides

Infrared and Raman spectra were obtained for n-C₃D₇I and n-C₄D₉I that showed the existence of rotational isomers. The conformer with a co-planar chain of carbons and iodine is the one stable in the crystals of both compounds, analogous to the protonated species. Vibrational assignments were made with the aid of normal coordinate calculations. Force constants were determined by simultaneously fitting the calculated to the observed frequencies for 155 values of the eight molecules, trans and gauche n-C₃H₇I, trans and gauche n-C ₃D₇I, TT and TG n-C₄H₉I, and TT and TG n-C₄D₉I. The average error for the 155 frequencies is 6.3 cm^?1.     

π-Cyclopentadienyls of nickel(II) : XIII. The preparation and properties of the compounds π-C5H5NiPBu3SC(S)X (X = OR,R and NRH) and π-C5H5NiPBu3SC(O)NRH

Compounds of the type π-C₅H₅NiPBu₃SC(S)X (X = R, OR and NRH) are obtained from reactions between [π-C₅H₅Ni(PBu₃)₂]⁺Cl^? and SC(S)X^? in aqueous solution. Compounds such as π-C₅H₅NiPBu₃SC(S)NRH are also obtained by reactions of π-C₅H₅NiPBu₃SH with RNCS.Reactions of C₆H₅NCS with π-C₅H₅NiPBu₃SEt or [π-C₅H₅NiPBu₃S(CH₂)_n]₂ (n = 1, 2 and 3) give π-C₅H₅NiPBu₃[SC(NC₆H₅)SC₂H₅] or [π-C₅H₅NiPBu₃ {SC(NC₆H₅)S(CH₂)_n}]₂ respectively.Similar reactions of π-C₅H₅NiPBu₃SH and RNCO given π-C₅H₅NiPBu₃SC(O)NRH.Treatment of π-C₅H₅NiPBu₃SC(S)R with HCl gives π-C₅H₅NiSC(S)R.     

Isomerization reactions of the n-C4H9O and n-OOC4H8OH radicals in oxygen

Reactions of n-C₄H₉O radicals have been investigated in the temperature range 343–503 K in mixtures of O₂/N₂ at atmospheric pressure. Flow and static experiments have been performed in quartz and Pyrex vessels of different diameters, walls passivated or not towards reactions of radicals, and products were analyzed by GC/MS. The main products formed are butyraldehyde, hydroperoxide C₄H₈O₃ of MW 104, 1-butanol, butyrolactone, and n-propyl hydroperoxide. It is shown that transformation of these RO radicals occurs through two reaction pathways, H shift isomerization (forming C₄H₈OH radicals) and decomposition. A difference of activation energies ΔE = (7.7 ± 0.1 (σ)) kcal/mol between these reactions and in favor of the H-shift is found, leading to an isomerization rate constant k_isom (n-C₄H₉O) = 1.3 × 10¹² exp(− 9,700/RT). Oxidation, producing butyraldehyde, is proposed to occur after isomerization, in parallel with an association reaction of C₄H₈OH radicals with O₂ producing OOC₄H₈OH radicals which, after further isomerization lead to an hydroperoxide of molecular weight 104 as a main product. Butyraldehyde is mainly formed from the isomerized radical HOCCCC˙ + O₂ ··· → O (DOUBLE BOND) CCCC + HO₂, since (i) the ratio butyraldehyde/(butyraldehyde + isomerization products) = 0.290 ± 0.035 (σ) is independent of oxygen concentration from 448 to 496 K, and (ii) the addition of small quantities of NO has no influence on butyraldehyde formation, but decreases concentration of the hydroperoxides (that of MW 104 and n-propyl hydroperoxide). By measuring the decay of [MW 104] in function of [NO] added (0–22.5 ppm) at 487 K, an estimation of the isomerization rate constant OOC₄H₈OH → HOOC₄H₇OH, κ₅ ≅ 10¹¹exp(−17,600/RT) is made. Implications of these results for atmospheric chemistry and combustion are discussed. © 1996 John Wiley & Sons, Inc.     

Combined Fourier transform infrared and Raman spectroscopic studies of some carbonyl-diphosphine-indenyl-iron cations

The Fourier transform infrared and Raman spectra of the cations [η⁵-C₉H₇Fe(CO)_n dppa]⁺ (n = 1, 2; dppa=bisdiphenylphosphinoalkane, where alkane=methane, ethane, butane, hexane and octane) and [{η⁵-C₉H₇Fe(CO)₂}₂-μ-dppa]²⁺ indicate that the alkyl chain lengths have effects on the structures of the bidentate cations resulting in increased back-donation to carbonyl groups as the chain length increases. In contrast the alkyl chain lengths have no similar effects in the unidentate mononuclear and bridged cations.     

NMR study of molecular motion in oriented long-chain alkanes. III. Oriented n-C32H66

The NMR second moment of a uniaxially oriented mat of single crystals of n-C₃₂H₆₆ (in the orthorhombic form) was measured at temperatures from ?170°C to 70°C and at various alignment angles γ between the orientation axis (preferential direction of the molecular chains) and the NMR magnetic field. Accurate expressions are given for the NMR second moment of an orthorhombic normal paraffin C_nH_2n+2 of arbitrary molecular chain length n for n ≥ 10, in the following states of molecular motion: no motion (a rigid lattice), rotation of CH₃ groups, and rotation of the chains around their axes with superimposed rotation of CH₃ groups. In addition to these well-known motions, n-C₃₂H₆₆ is found to exhibit an α process. The corresponding decrease of the NMR second moment shows the dependence on γ predicted for “flip-flop” motion, i.e., rotational jumps of the chain molecules around their axes through 180° and a simultaneous translation along these axes by one CH₂ group. The overall decrease in second moment occuring at the transition to the hexagonal rotator phase in n-C₃₂H₆₆ can be quantitatively accounted for. The dependence of this decrease on the alignment angle γ, however, is in disagreement with calculations based on a simple rotation of the chains around their axes. Considerable torsion of the chains superimposed on the rotation would improve agreement between theory and experiment.     

Metallcarbonyl-synthesen : V. Die reduktive hochdruckcarbonylierung von (η5-C5H5)NbCl4 als einfache und leistungsfähige synthesemethode für (η5-C5H5) Nb(CO)4. Darstellung der isotopenmarkierten derivate (η5-C5H5) Nb(CO)4 − n(13CO)n und (η5-C5H5) Nb(CO)4 − n(13C18O)n

The reductive high-pressure carbonylation of tetrachloro(η⁵-cyclopentadienyl)niobium using sodium as reduction agent and Cu/Al mixture as halogen acceptor system cleanly yields tetracarbonyl (η⁵-cyclopentadienyl)niobium which can be synthesized by means of this new procedure on a 35 g-scale, with yields ranging between 89 and 94%. Under photolysis conditions, (η⁵-C₅H₅) Nb(CO)₄ is converted into the solvent complex (η⁵-C₅H₅) Nb(CO)₃THF which, in turn, incorporates ¹³Co or ¹³C¹⁸O under mild conditions to give the labelled derivatives (η⁵-C₅H₅) Nb(CO)_{4 ? n}(¹³CO)_n and (η⁵-C₅H₅) Nb(CO)_{4 ? n}(¹³C¹⁸O)_n, respectively.     

Photochemistry of methyl- and n1-benzyl-n5-cyclopentadienyltricarbonyltungstein(II)

Irradiation of solutions of n⁵-C₅H₅W(CO)₃R (R  CH₃n1-CH₂C₆H₅) in cyclohexane at ca. 310490 nm leads to the formation of [n⁵-C₅H₅W(CO)₃]₂ and methane and of n⁵-C₅H₅W₅(CO)₂(n³-CH₂C₆H₅) and some [n⁵-C₅H₅W(CO)₃]₂, respectively. When the irradiation is carried out in the presence of excess P(C₆H₅)₃, the photoproducts are n⁵-C₅H₅W(CO)₂[P(C₆H₅)₃]CH₃ (R  CH₃) and n⁵-C₅H₅W(CO)₂(n₃-CH₂C₆H₅) and trace [n⁵-C₅H₅W(CO)₃]₂ (R  n¹-CH₂C₆H₅). Photolysis of the n⁵-C₅H₅W(CO)₃R in the presence of benzyl chloride affords n⁵-C₅H₅W(CO)₃Cl (R  CH₃) and both n⁵-C₅H₅W(CO)₂(n³-CH₂C₂H₅) and n⁵-C₅H₅W(CO)₃Cl (R  n¹-CH₂C₆H₅), the relative amounts of the latter products depending on the quantity of added C₆H₅CH₂Cl. Irradiation of n⁵-C₅H₅W(CO)₃-CH₃ in the presence of both P(C₆h₅)₃ and C₆H₅CH₂Cl affords n⁵-C₅H₅W(CO)₂-[P(C₆H₅)₃]CH₃, but no n⁵-C₅H₅W(CO)₃Cl. It is proposed that the primary photo-reaction in these transformations is dissociation of a CO group from n⁵-C₅H₅W-(CO)₃R to generate n⁵-C₅H₅W(CO)₂R, which can either combine with L to form a stable 18 electron complex, n⁵-C₅H₅W(CO)₂(L)R (L  CO, P(C₅H₅)₃; LR  n³-CH₂C₆H₅), or lose the group R in a competing, apparently slower step. This proposal receives support from the observation that, light intensifies being equal, n⁵-C₅H₅W(CO)₃CH₃ undergoes a considerably faster photoconversion to [n⁵-C₅H₅W(CO)₃]₂ under argon than under carbon monoxide.     

Intramolecular energy band dispersion of n-C36H74 observed by angle-resolved photoemission with synchrotron radiation

The energy band dispersion E = E(k) is determined for the valence bands in a long-chain alkane n-C₃₆ H₇₄ by angle-resolved photoemission from an oriented polycrystalline sample using synchrotron radiation. Comparison with theoretical calculations for a single chain shows good qualitative agreement for the position, width, and dispersion of the valence band. This is the first observation of energy band dispersion in an organic molecular solid.