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.     

Quantum chemical calculations of the molecular structures of hybrid amino acid derivatives of fullerene C60

The stereoselectivity of the formation of hybrid amino acid derivatives of fullerene (AADF) C₆₀ was studied. The energies of the model addition reactions C₆₀ + n C₂H₆ ? Me _n -C₆₀-Me _n (1) and C₆₀ + n EtNC₄H₇Me ? Et _n -C₆₀-(NC₄H₇Me) _n (2) (n = 1–3) were calculated by the DFT method B3LYP/6-31G*. The most stable products of reaction (1) are hexamethylated fullerene derivatives in which five Me groups are arranged in the form of a regular pentagon. Among the AADF obtained by reaction (2), 1,4-disubstituted fullerene isomers are most stable. The molecular structures of such isomers were calculated for six biologically active hybrid AADF; the solvent contact areas of these molecules were evaluated.     

Ab initio SCF MO results for the carborane isomers 3,5-C2B6H8, 1, 7-C2B7H9, and 1,2-C2B7H9

We report the geometry-optimized total energies and bond distances for the closo-carborane isomers 3,5-C₂B₆H₈, 1,7-C₂B₇H₉, and 1,2-C₂B₇H₉ calculated by the ab initio SCF MO method using the STO -3G basis set. Relative energies are compared with those of the other carborane isomers in the 8- and 9- atom classes. These results complete the set of calculations at the same level of theory for all deltahedral carborane isomers except for those of the 11-atom class.     

Aromaticity and ring currents in ferrocene and two isomeric sandwich complexes

Ring currents induced in the ferrocene molecule and its two hypothetical isomers (η⁴-C₄H₄)Fe(η⁶-C₆H₆) and (η³-C₃H₃)Fe(η⁷-C₇H₇) by an external magnetic field directed along the principal axis are plotted within the ipsocentric approach (at the B3LYP/6-31G∗∗//B3LYP/6-31G∗∗ level). The carbocyclic ligands in all three species are found to be aromatic, i.e. to support individual diatropic ring currents, with formal charges that are consistent with the 4n + 2 rule and the +2 oxidation state of iron.     

Vibrational and calorimetric study of phase transitions in n-C6F14 and n-C8F18 crystals

Heat capacities of n-perfluorohexane and n-perfluorooctane were measured from 4.2 K to room temperature. One solid—solid transition is found for n-C₆H₁₄,two for n-C₈F₁₈. Spectra show that the molecules have the same conformations in the two forms of n-C₆F₁₄. Several isomers are present in the high-temperature forms of n-C₈F₁₈;thus transitions in this compound have order—disorder character.     

Synergistic complexes of uranyl ion with 1-phenyl-3-methyl-4-acetyl-pyrazolone-5 and some oxo-donors

Complexes of uranyl ion with 1-phenyl-3-methyl-4-acetyl-pyrazolone-5(PMAP) and various oxo-donors such as aliphatic sulphoxides [R₂SO, where R = i-C₅H₁₁(DISO), n-C₆H₁₃(DHSO), n-C₇H₁₅(DSSO), n-C₈H₁₇(DOSO), n-C₉H₁₉(DNSO), n-C_1OH₂₁(DDSO), n-C₁₁H₂₃(DUDSO) and n-C₄H₉(DBUSO)] tributylphosphate (TBP) and tri-n-octyl phosphine oxide (TOPO) have been synthesised and characterized. Analytical data establish that they have the stoichiometry UO₂(PMAP)₂X where X is the oxo-donor. The IR spectra of the sulphoxide complexes in the SO stretching region indicate that the ligands R₂SO are O-bonded. The methyl protons of the pyrazole ring and acetyl group in the PMAP ligand are equivalent giving rise to a single sharp peak in the PMR spectra, whereas in the synergistic complexes with the oxo-donors, two deshielded peaks of equal intensity are observed which indicate the non-equivalence of the methyl groups. The peak which is more deshielded has been ascribed to the methyl of the acetyl group. The higher deshielding of these methyl protons arises due to the transfer of electron density to the metal atom on complexation.     

Reaction of dichloromanganese(IV) Schiff-base complexes with water as a model for water oxidation in photosystem II

The dichloromanganese(IV) Schiff-base complexes Mn(N-R-3-NO₂ sal)₂Cl₂ (R = n-C₃H₇, n-C₄H₉, n-C₆H₁₃,     

Synthesis and molecular structures of heptafluoropropylated fullerenes: C70(n-C3F7)8, C70(n-C3F7)6O, and C70(C3F7)4

Ampoule reactions of C₇₀ with n- and i-C₃F₇I were carried out at 250-310 °C. Two step HPLC separations allowed the isolation of several C₇₀(n-C₃F₇)_4-8 and C₇₀(i-C₃F₇)₄ compounds. Crystal and molecular structures of C₇₀(n-C₃F₇)₈-V, C₇₀(n-C₃F₇)₆O, C₇₀(n-C₃F₇)₄, and three isomers of C₇₀(i-C₃F₇)₄ have been determined by X-ray crystallography using synchrotron radiation. Molecular structures of the new compounds were compared with the known examples and discussed in terms of addition patterns and relative energies of their formation.     

Gas-phase solvation of Cl− with H2O,CH3OH,C2H5OH,i-C3H7OH,n-C3H7OH,and t-C4H9OH

The gas-phase clustering reactions Cl⁻ (ROH)n−1 + ROH ⇄ Cl⁻ (ROH)_n with n ⩽ 11 for ROH = H₂O, CH₃OH, C₂H₅OH, i-C₃H₇OH, n-C₃H₇OH, and t-C₄H₉OH were measured using a high-pressure mass spectrometer. It seems likely that for CH₃OH and C₂H₅OH, six ligands complete the shell structure and that ligands with n ⩾ 7 belong to the outer shell. The bond energies D(ROH---Cl⁻) increase in the order H₂O < CH₃OH < C₂H₅OH < i-C₃H₇OH < t-C₄H₉OH < n-C₃H₇OH. The observed strong bond of n-C₃H₇OH---Cl⁻ may be due to the fact that both the acidic hydrogen atoms in the −OH and terminal −CH₃ of n-C₃H₇OH interact with Cl⁻ with the most favorable configuration. For Cl⁻ switching reactions, Cl⁻ (H₂O)_n + (ROH)_n ⇄ Cl⁻ (ROH)_n + (H₂O)_n, the ΔG⁰_n values converge to the values of free energies of transfer of Cl⁻ from water to ROH solvent ( = ΔG⁰_n with n → ∞) with n ≈ 7. The observed convergence of ΔG⁰_n is due to compensation of changes in enthalpy and entropy, i.e. both ΔH⁰_n and TΔS⁰_n show increasing divergence from the values of enthalpies and entropies of transfer of Cl⁻ from water to ROH solvent, respectively, with n = 1 → 7. This is due to the stronger interactions of ROH with Cl⁻ than that of H₂O in the inner shell of Cl⁻ (ROH)_n at the expense of the less favorable entropy changes (less freedom of motion for ligands in the inner shell).     

Reactions of fluorine atoms with iodides studied by crossed beam laser-induced fluorescence

The reactions of F atoms with C₂H₅I, C₂F₅I, and n-C₃H₅I were studied by the crossed beam laser-induced fluorescence techniques within the 570–620 nm wavelength region. The vibrational and rotational excitation spectra of the reaction product IF were measured. The relative vibrational population densities of v = 3,4, and 5 vibrational levels, and some of the relative detailed vibrational rate constants, the rotational temperatures, and the mean fractions of rotational energy in individual vibrational states of the reaction product IF were obtained. The reaction mechanism was discussed.     

NMR investigation of bis(2,3-alkanedione dioximato)-bis(pyridine)cobalt(III) iodide complexes: 1H and 13C NMR spectra and 13C spin-lattice relaxation time measurements

The complexes of trans-[Co(III)(R,CH₃-dioxH)₂(py)₂]I2 (R = CH₃, C₂H₅, n-C₃H₇ and n-C₄H₉) were investigated in solution by ¹H and ¹³C NMR spectra and ¹³C spin-lattice relaxation time measurements. The ¹H and ¹³C-resonances of the R = C₂H₅, n-C₃H₇ and n-C₄H₉) groups were shifted to higher field than those of the free ligands by the complexation; it was attributable to the ring current shielding due to the axial pyridine ligands of the complexes. ¹³C spin-lattice relaxation times were interpreted as due to movement of the axial pyridine ligands as if they twist around the CoN (pyridine nitrogen) bond axis and the above R groups were moving segmentally. These segmental movements allowed the R groups to approach closely toward the axial pyridine ring plane to experience the ring current shielding.     

Tin(IV) complexes of schiff bases derived from pentane-2,4-dione or 2-hydroxy-1-naphthaldehyde

The 1∶2 molar reactions of tin(IV) chloride with the Schiff bases, CH₃C(OH):CHC(CH₃):NR and 2 HOC₁₀H₆CH:NR′ (where R=C₂H₅,n-C₃H₇ orn-C₄H₉ and R′=C₆H₅, C₂H₅,n-C₄H₉ ort-C₄H₉) have resulted in the synthesis of SnCl₄·(SBH)₂ type derivatives (whereSBH represents the Schiff base molecule). These have been characterized by elemental analysis, conductivity measurements and IR spectral studies.     

Onium Sulfates and Hydrogen Sulfates: Products of Reactions of Sulfur(IV) Oxide with Aqueous Solutions of Alkylamines and Aniline

The reaction products formed in the SO₂–L–H₂O–O₂ systems (L is n-propylamine, n-butylamine, tert-butylamine, n-heptylamine, n-octylamine, aniline) were isolated and identified as “onium” salts [n-C₃H₇NH₃]₂SO₄, [n-C₄H₉NH₃]₂SO₄, [t-C₄H₉NH₃]₂SO₄, [n-C₇H₁₅NH₃]₃SO₄(HSO₄), [n-C₈H₁₇NH₃]₃SO₄(HSO₄), and [C₆H₅NH₃]₂SO₄. The products were characterized by elemental analysis, IR and Raman spectroscopy, mass spectrometry, and thermogravimetry.     

The palladium-catalysed cross-coupling reaction of lithium polyfluorophenyltrimethoxyborates with 4-fluoroiodobenzene

Li[C₆F₅B(OMe)₃], Li[C₆HF₄B(OMe)₃] (all three isomers) and Li[3,4,5-C₆H₂F₃B(OMe)₃] are the first examples of polyfluorophenyltrimethoxyborate salts which have been applied as reagents to Pd-catalysed cross-coupling reactions. A series of polyfluorinated biphenyls C₆H_5−nF_n-C₆H₄F-4′ were obtained from Li[C₆H_5−nF_nB(OMe)₃] and the model substrate 4-FC₆H₄I in the presence of Pd catalysts. The influence of the number and the position of fluorine atoms in the polyfluorophenyltrimethoxyborate salts on the reactivity in the coupling reaction was elucidated.     

A thermogravimetric study of lithium tetraalkoxyborates

Properties of lithium tetraalkoxyborates Li[t-C₄H₉OB(OR)₃] (R = n-C₄H₉ to n-C₈H₁₇, n-C₁₂H₂₅) were studied by differential thermogravimetry. The kinetic parameters and heat effects of thermal decomposition of lithium tetraalkoxyborates in air and inert gas atmosphere as functions of the carbon chain length were determined.     

Molecular structure and IR absorption spectra of perfluorinated aldehyde hydrates (n-CxF2x+1CH(OH)2, x = 1-4)

Structures and IR absorption spectra of the conformational isomers of perfluorinated aldehyde hydrates, n-C_xF_2x+1CH(OH)₂, (x = 1-4) have been calculated using density functional theory (DFT) and compared to experimental FT-IR measurements. Two absorption peaks around 3600-3700 cm⁻¹ were observed and are assigned to OH stretching modes of OH groups with, and without, intramolecular hydrogen bonding. For n-C₃F₇CH(OH)₂, two absorption bands around 900-1000 cm⁻¹ were observed in the experimental spectra, whereas only a single in-phase stretching mode of the (CF₃)(C₂F₄CH(OH)₂) and (C₃F₇)(CH(OH)₂) bonds was calculated for each conformer. The experimental spectra were well described by composite spectra of the thermal equilibrium mixture of different conformational isomers of n-C_xF_2x+1CH(OH)₂ calculated by DFT.     

Influence des interactions attractives non liees sur les stabilites relatives d'ethers et d'acetates d'enol renfermant un groupe styryle

The measure of relative stabilities of β-alcoxystyrene isomers I: C₆H₅-CHCH-OR shows that the trans compound is the most stable when RCH₃ and C₂H₅ and the cis compound is the most stable when Ri-C₃H₇ and t-C₄H₉. The orientation of the OR group can be determined by RMN ¹³C. The stabilities of these molecules are discussed in terms of non bounded attractive interactions. This interpretation is confirmed by the measure of relative stabilities of α-methyl β-alcoxy (and acetoxy)-styrene isomers II: C₆H₅-C(CH3)CH-OR. (RCH₃, C₂H₅ et COCH₃).     

On the stabilization of carbanions by adjacent phenyl,cyano, methoxy-carbonyl,and nitro groups in the gas phase

Institute of Mass Spectrometry, University of Amsterdam, Amsterdam, The Netherlands By using the method of Fourier transform ion cyclotron resonance mass spectrometry, substituent stabilization energies of homologous series of cycloalkyl carbanions, Ξ-c-C_nH_2n?2 (n = 3, 4, 5, 6, 7) with π-accepting substituents (Ξ = Ph, CN, COOMe, NO₂) have been determined experimentally in the gas phase as the difference between the proton affinity of the substituted and corresponding unsubstituted (Ξ = H) cycloalkyl carbanions. The stabilization energy data have been analyzed in terms of Taft’s parametrization of polarizability, field/inductive, and resonance effects. The linear regression analyses show excellent correlations within the ΞCH₂ ^? Ξ-c-C_nH_2n?2 ^? (n = 4, 5, 6, 7), and Ξ-c-C₃H₄ ^? carbanion series, from which it appears that the contributions of polarizability effects are independent of the above type of carbanions and only depend on the nature of the substituent. Further, it follows that inductive stabilization is more effective in the substituted methyl, ΞCH₂ ^?, than in the substituted cycloalkyl, Ξ-c-C_nH_2n?2 ^? (n = 4, 5, 6, 7) carbanions. This result suggests that inductive stabilization is counteracted by the electron releasing effect of alkyl groups. Resonance stabilization is significantly more effective in the substituted cycloalkyl, Ξ-c-C_nH_2n?2 ^? (n = 4, 5, 6, 7), than in the substituted methyl, ΞCH₂ ^?, carbanions, which suggests that m contrast to inductive stabilization, resonance stabilization is assisted by the electron releasing effect of alkyl groups. Finally, it appears that substitutent stabilization in the geometrically restricted substituted cyclopropyl carbanions, Ξ-c-C₃H₄ ^?, is dramatically less effective than in the corresponding geometrically unrestricted larger substituted cycloalkyl carbanions, Ξ-c-C_nH_2n?2 ^? (n = 4, 5, 6, 7). The linear regression analyses of the substituted cycloalkyl carbanions indicate that reduction of the stabilization energy is caused not exclusively by a geometrically hindered resonance stabilization, but also to a smaller extent by a less efficient inductive stabilization in the substituted cyclopropyl carbanions.     

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.     

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.