Structure and conformation of 1-Bromopropane: A gas-phase electron-diffraction investigation using microwave-spectroscopy data and results from ab initio calculations as constraints

1-Bromopropane has been studied by gas-phase electron diffraction (ED) at 24C. Earlier published values for rotational constants from microwave spectroscopy (MW), together with results from ab initio molecular-orbital calculations, have been included in the ED analysis. Two conformers with C-C-C-Br torsion angles of 180 (anti) or 66.0(17) (gauche) have been observed. The results obtained for the bond distances (r _g) and valence angles () from this combined ED/MW analysis, with the ab initio results used as constraints are r (C-H)=1.114(9) å,r(C₁-C₂)=1.521(5) å,r(C₂-C₃)=1.535(5) å,r (C₁-Br)=1.962(6) å, <(C-C-C)anti,=110.0(11), <(C-C-C)gauche=113.3(11), < (C-C-Br)anti=111.1(6), < (C-C-Br)gauche=112.1(6), <C₂-C₁-H=112.1 (ab initio value), <C₂-C₃-H=111.4 (ab initio value), <H-C₂-H=107.0 (ab initio value). Error limits are given as 2, where (standard deviation) includes estimates of uncertainties in voltage/height measurements and correlation in the experimental data. The observed amountof gauche conformer was 64(14)%. Using the entropy difference between conformers obtained in the ab initio calculations, this composition corresponds to an energy difference of E=E _anti —E _gauche=0.03(36) kcal/mol. The results are compared with those earlier obtained for other 1-halopropanes.     

Structure and Magnetic Properties of Solid Solutions of Molecular Magnetics Based on Ni(II) and Co(II) Complexes with Nitroxyl Radicals

Ni(II) and Co(II) complexes with deprotonated paramagnetic enaminoketones 4(3,3,3trifluorine2oxopropylidene) 2,2,5,5tetramethyl3imidazolidine1oxyl (L) and 4(3,3,3trifluorine1chlorine2oxopropylidene)2,2,5,5tetramethyl3imidazolidine1oxyl (L¹) and alcohols are shown to form continuous solid solutions Ni_xCo_1-xL₂(C₂H₅OH)₂ and Ni_xCo_1-xL₂ ¹(CH₃OH)₂. Single crystal Xray diffraction analysis showed that concentration variation practically does not affect the structural characteristics of the solid solutions. Distinguishing features if the magnetic behavior of Ni_xCo_1-xL₂ · (C₂H₅OH)₂ and Ni_xCo_1-xL₂ ¹(CH₃OH)₂ are the antiferromagnetic interaction of the moments of the nickel and cobalt sublattices inside the polymeric layers and the antiferromagnetic nature of interlayer interaction of the magnetic moments.     

Calculations of induced moments in large molecules I. Polarizabilities and second hyperpolarizabilities in some alkanes

We report the results of coupled Hartree-Fock computations for the average polarizability, , and hyperpolarizability, , of CH₄, C₂H₆, C₃H₆ and C₃H₈. The Hamiltonian matrices are constructed from an extended CNDO model. Small as well as large basis sets were tested. Agreement with available experimental values is within 13% for and 31% for .     

Reversed phase liquid chromatographic retention behavior of polystyrene homopolymers

Summary Isocratic and gradient elution high performance liquid chromatographic measurements of the retention behavior of polystyrene homopolymers with molecular weights ranging from 2 kD to 390 kD were performed using mixed methylene chloride-methanol mobile phases of varying composition and a C-18 chemically bonded stationary phase supported on either 100 Å or 300 Å mean pore diameter silica. Isocratic measurements of the capacity factor, k, for different molecular weight homopolymers as a function of the volume fraction of methylene chloride, , permit determination of the critical composition, _c, which renders k=1 and the local slope, S=–lnk/_c of the lnk- isotherm at =_c, and also the dependence of _c and S on the degree of polymerization, M. Linear gradient elution measurements of _c and S were also performed and compared to the corresponding isocratic measurements. The general retention behavior and the dependence of _c and S on M compare favorably to the predictions of the theory of homopolymer retention and fractionation developed by Boehm, Martire, Armstrong, and Bui (BMAB). Comparison is also made between the present work and the experimental observations of other workers on related chromatographic systems involving hompolymer retention.     

Crystal Structures of [Ni(Phen)(i‐Bu2PS2)2] and [Ni(Phen)3](i‐Bu2PS2)2 Complexes and Interaction between Coordinated 1,10‐Phenanthroline Molecules

Single crystals of [Ni(Phen)(iBu₂PS₂)₂] (I) and [Ni(Phen)₃](iBu₂PS₂)₂ (III) compounds were grown, and their structures were determined by Xray diffraction analysis (CAD4 diffractometer, MoK radiation, 3336 F _hkl , R = 0.0373 for I and 2575 F _hkl for III). The crystals of complex I have a triclinic unit cell with the following parameters: a = 11.097(1) , b = 14.903(2) , c = 22.650(3); = 75.18(1)°, = 80.50(1)°, = 75.07(1)°, V = 3479.2(7)³, Z = 4, _calc = 1.255 g/cm³, and space group 1; the crystals of III have a monoclinic unit cell with the following parameters: a = 19.010(3), b = 15.481(1) , c = 17.940(3); = 97.58(1)°, V = 5233.5(12)³, Z = 4, _calc = 1.292 g/cm³, and space group C2/c. The structure of complex I is built from mononuclear molecules, and the structure of III, from [Ni(Phen)₃]²⁺ complex cations and i Bu₂PS₂ ^- outersphere anions. The NiN₂S₄ coordination polyhedra in the structure of I and NiN₆ in the structure of III are distorted octahedra. Based on structural data, the interaction between the coordinated Phen molecules of complexes I, [Ni(Phen)₂(iBu₂PS₂)](iBu₂PS₂) (II), and III is considered, as well as the packing modes of these complexes.     

Triterpene glycosides and their genins fromThalictrum foetidum. V. Structure of cyclofoetoside B

A new glycoside (cyclofoetoside B) (I) has been isolated from the epigeal part of the plantThalictrum foetidum L. (Ranunculaceae). On the basis of chemical transformations and with the aid of physicochemical characteristics it has been established that cyclofoetoside B is 24S-cycloartane-3, 16, 24, 25, 29-pentaol 3-O--L-arabinopyranoside 16-O-[O--L-rhamnopyranoside-(1 6)--D-glucopyranoside], C₄₇-H₈₀O₁₇, mp 194–197°C (methanol); [] _D ²⁴ +15.7 ± 2° (c 0.88; pyridine). The enzymatic hydrolysis of (I) has yielded cyclofoetigenin B (III), 24S-cycloartane-3,16,24,25,29-pentaol 16-O--D-glucopyranoside, (IV), C₃₆H₆₂O₁₀, mp 223–225°C (acetone), [] _D ²⁴ +37 ± 2° (c 0.97; methanol) and 24S-cycloartane-3,16,24,25,29-pentaol 16-O-[O--L-rhamnopyranosyl-(1 6)--D-glucopyranoside, C₄₂H₇₂O₁₄, mp 229–231°C (methanol), [] _D ³⁰ +41 ± 2° (c 0.7; methanol). Details of the IR and¹H and¹³C NMR spectra of the compounds are given.Irkutsk Institute of Organic Chemistry, Academy of Sciences of the USSR. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Trashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 341–345, May–June, 1986.     

Order and disorder in mixed metal linear chains: The homo and heterobimetallic EDTA (M(H2O)4OIOII)[M′(EDTA)] · 6H2O complexes (M = Mg,Mn, Co,Zn and Ni; M′ = Co,Ni, Cu and Zn)

Summary Polymetallic solid solutions of the ethylenediaminetetracetic acid (EDTA) and six divalent metal ions exist in the range: MgMnCoZnNiCu(EDTA) · 6H₂O where + + + + + =2, 01, 0,,2, 0, 1.This type of structure is characterized by the presence of two different octahedral carboxylate-bridged coordination sites forming infinite zig-zag chains. Visible and i.r. spectra and t.g.a. analysis show that there is occupational preference for the two coordination sites in the crystalline structure.Due to this preference, and also to the structural features, the heterobimetallic MM(EDTA) · 6H₂O compounds constitute a structurally new class of materials which can be described as ordered alternating-heterobimetallic polymeric coordination complexes.     

Crystalline Inclusion Compounds Derived from 1,1'-Bis(ethenyl-2-pyridyl)ferrocene and (±)-1,1'-Bi-2-naphthol in Different Solvents

Crystallization of organometallic dipyridine(1,1'-bis(ethenyl-2-pyridyl)-ferrocene) (1) with(±)-1,1'-bi-2-naphthol (2) from EtOH,i-PrOH, (±)-2-BuOH, and MeOH forms crystallineinclusion compounds of stoichiometries1 2 C₂H₅OH (3, 1 2 C₃H₇OH (4),1 2 C₄H₉OH (5),and 1 2 CH₃OHH₂O(6), respectively. Thecrystalline species 3, 4, and 5 areisostructural with the three molecular componentsinterlinked by hydrogen bonds to form a columnarstructure. In 6, the four molecular componentsare interlinked by hydrogen bonds to form atwo-dimensional framework structure.     

Apparent molar heat capacities and volumes of electrolytes and ions int-butanol-water mixtures

The apparent molar volumes V and heat capacities C _p, of NaCl, LiCl, NaF, KI, NaBPh₄ and Ph₄PCl have been determined in solutions of H₂O containing up to 40 mass% t-butyl alcohol (TBA) by flow densitometry and flow microcalorimetry. Combination of these results with literature data allows calculation of V and C _p, for 16 ions in these mixtures using the assumption that _tX(Ph₄P⁺) = _tX(BPh ₄ ^– ) where X=V or C _p and _tX is the change in X for a species on transfer from H₂O to TBA-H₂O mixtures. These are the first reported single ion values for C _p, in a mixed solvent. While whole electrolyte volumes and heat capacities show relatively smooth changes with solvent composition, _tX(ion) exhibit two well-developed extrema at around 10 and 25 mass% TBA. The shape of the _tX(ion) curves shows considerable uniformity among the alkali metal cations and the halide ions but the extrema become more pronounced with increasing size among the tetraalkylammonium ions. These extrema are analogous to those observed in aqueous organic mixtures of surfactants and are probably indicative of microphase transitions in these strongly interacting solvent mixtures.     

Thermodynamic properties of water-β-cyclodextrin-dodecylsurfactant ternary systems

Densities, heat capacities and conductivities of water-surfactant--cyclodextrin (-CD) ternary systems were determined at 25°C. The surfactants studied were sodium dodecylsulfate (NaDS) and dodecyltrimethylammonium bromide (DTAB). From conductivity data, apparent critical micelle concentrations (cmc^*) and degree of ionization of micelles were obtained at a fixed -CD concentration (m_CD). From the cmc^* value and that in water (cmc) the stoichiometry of the surfactant--CD complex was calculated. At a given m_CD, the apparent molar volume V_,CD and heat capacity C_,CD of -CD in the two surfactants were calculated as functions of surfactant concentration m_S. For both NaDS and DTAB, V_,CD increases with m_S up to about the cmc beyond which it decreases to a constant value at high m_S, the opposite is observed for C_,CD. With NaDS, a jump in the C_,CD vs, m_S trend was detected and ascribed to a structural NaDS micellar transition. The apparent molar volume V_S and heat capacity C_S of NaDS and DTAB in the water--CD mixture 0.017 m were also obtained. From these properties and those in pure water, the volume V_S and heat capacity C_S of transfer of the surfactant from water to water+-CD mixture as functions of m_S were calculated. For both surfactants, the V_S vs. m_S trends increase to the cmc and then decrease in a monotonic manner, whereas C_S increases regularly with m_S in the pre-micellar region and is essentially constant in the post-micellar region. The V_S vs. m_S trends were qualitatively explained in terms of dispersed, complexed and micellized surfactant contributions.     

Effect of the organic modifier on the retention of retinoids in reversed-phase liquid chromatography

Summary The retention of retinoids in reversed-phase liquid chromatography was studied using aqueous mobile phases of different composition (methanol 94–86% and acetonityrile 92–82%) at five temperatures (40–60 °C). With both organic modifiers the effect of the molecular structure increased as the water content and the polarity of the mobile phase increased. The temperature-dependence increased in the same manner with aqueous acetonitrile mobile phases. The - interactions between the retinoids and acetonitrile diminish when the water content of the mobile phase is increased, as happens also to the hydrophobic interactions with both organic modifiers. The net effect of these changes depends on the composition of the mobile phase. There was excellent correlation of retention with all polarity parameters studied(, P, x_e, x_d, x_n, E _T ^N , _T, , _o and _d), when the calculations were made separately with methanol and acetonitrile. The volume fraction of the organic modifier, , was the only parameter describing the retention well in both organic modifiers simultaneously.     

Calculation of retention indices and peak widths in temperature programmed gas-liquid chromatography

Summary Isothermal chromatographic measurements lead directly to H _v ^o and A (entropy term) of solutes, and three constants of an empirical relationship between peak width and column temperature. From the thermodynamic parameters H _v ^o and A retention temperatures have been computed by means of a theoretical model including temperature dependence of carrier gas viscosity, and subsequently retention times; programmed retention indices have been determined by linear and polynomial interpolations. By substituting the value of the calculated retention temperature in the above-mentioned relationship, peak width at half-height for a linear temperature may be estimated. Predicted retentions correlate with observed data, with a P-value 0.01; simulation accuracy is generally 6–10% for peak widths.Retention indices of some organochlorine species, separated on an OV-101 capillary column, may differ by as much as 26 units depending on the method of calculation. Polynomial-calculated indices are more consistent with the retention index scheme, and have smaller standard deviations and better constancy at different heating rates.     

1A1⇔5T2 Spin Transition in Heterometallic Solid Phases FexNi1-x(Htrz)3(NO3)2 · H2O (Htrz = 1,2,4‐Triazole)

Solid phases Fe_xNi_1-x(Htrz)₃(NO₃)₂ · H₂O (0.4 x 0.8$) and Ni(Htrz)₃(NO₃)₂ · H₂O were synthesized and studied. The phases were studied by means of magnetochemistry, powder Xray difraction analysis, and electronic and IR spectroscopy. The heterometallic phases are described by the stoichiographic method of differentiating dissolution (DD). The values of x were determined by two methods — atomic absorption and DD. Magnetochemical data showed that the solid phases exhibit a hightemperature ¹A₁ ⁵T₂ 0.5 x 0.8 and disappears at x = 0.4. The spin transition is accompanied by thermochromism (color changed from pink to white at 0.6 x 1 and from pink to light lilac at x = 0.5). A decrease in x leads to a decrease in the temperature of the forward (under heating T_c ) and reverse (under cooling T_c ) transitions, a decrease in hysteresis value ( T_c), and a smearing of the spin transition.     

A systematic treatment of three-dimensional quantum mechanical reaction coordinates

Summary The rigorous, collinear, canonical point transformation method with hyper-hyperbolic coordinates is extended to the infinite central mass problem in three dimensions. The initial transformation performed is (x_A, y _A, z _A, x _C, y _C, z _C) (, , , r, R, ), where (, , ) are the Euler angles; r and R are the AB and BC interatomic distances, respectively, and is the angle between r and R. A second transformation is then performed to (, , , , , ), where is the reaction coordinate mimicking the reaction path, and is the vibrational coordinate of the diatom. The transformed spaces are all one-to-one mappings from the original spaces, and thus do not have any three-to-one regions. The transformed momenta and Hamiltonians are derived, and are Hermitian in their respective transformed spaces.     

Contribution of adsorption to retention data in glass capillary gas chromatography part. I. Polar stationary phases

Summary The influence of the film thickness of Carbowax 20M coated onto glass surfaces (series of columns with different mode of surface treatment) upon the retention indices of solutes which exhibit tendency to hydrogen bonding has been investigated. Limiting values of Kovats indices, I, are calculated for all the columns examined.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Structure and charge distribution of some alkynoyl cations

We have performedab initio calculations to determine the structure and charge distribution of some alkynoyl cations and their parent alkynoyl fluorides. We have used Mulliken population analysis and a new technique developed by Yáñez, Stewart and Pople. Our results indicate that the mesomeric form O⁺C–CC–R is one of the most important contributors to the structure of these cations, in agreement with experimental conclusions. We have also found that the participation of mesomeric form O=C=C=C⁺ -R is not negligible and increases with -substitution. In the 3-phenylpropynoyl cation substantial delocalization of charge into the phenyl group occurs. Calculations from YSP population analysis are in good agreement with experimental evidence.     

Reactivity of chemisorbed hydrogen species on Pt towards acetylene

In the presence of both molecular and atomic hydrogen on catalyst surface, C₂H₂ is hydrogenated directly to C₂H₆. In the presence of atomic hydrogen only, the reaction can also have another route to form C₂H₄.

---

, C₂H₂ C₂H₆, , C₂H₄.

     

Steroid glycosides from the starfishEchinaster sepositus

Two new steroid glycosides, which have been called echinasterosides B₁ and B₂ have been isolated from the starfishEchinaster sepositus. Using chemical transformations (methylation, hydrolysis) and also spectral methods (¹H and¹³C NMR spectroscopy and GLC-MS) the complete chemical structure of B₁ has been established as 15-acetoxy-5-cholestane-3,4,6,8,24-pentaol 24-O[O-(2)O÷ methyl--D-xylopyranosyl)-(13)--L-arabinofuranoside] (I) and that of glycoside B₂ as 5-cholestane-3,4,6,8,15,24-hexaol 24-O-[O÷(2-O-methyl--D-xylopyranosyl)-(13)--L-arabinofuranoside] (II).Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Pirodnykh Soedinenii, No. 2, pp. 246–249, March–April, 1987.     

Zur Reaktion von Fluorsilanen mit lithiierten Aminen

The reaction of fluorosilanes with lithium salts of bulky amines like tetramethyl-piperidine and di-tert. butylamine leads to stable aminofluorosilanes of the type R-SiF₂-NRR [R=F, C(CH₃)₃, C₆H₅, C₆H₄N(CH₃)₂]. Lithium salts of silylamines react analogously: R₂Si(NR-SiF₂R)₂ (R=R= =CH₃, R=C₆H₅). An eight membered Si–N-ring is obtained in the reaction of a disubstituted silylaminofluorosilane with the dilithium salt of a silylamine. The mass-,¹H-, and¹⁹F-NMR spectra of the above mentioned compounds are reported.