On the 60th Birthday of F. I. Danilov

Russian Journal of Electrochemistry -     

The dark reactions F2 + CF3I,C2F5I,and n-C3F7I

The reactions between F₂ and the lowest members of the homologous series of perfluoroalkyl iodides (CF₃I, C₂F₅I, and n-C₃F₇I) have been studied. For these compounds, an exponential decrease in the alkyl iodide concentration over time following an induction period is observed for certain experimental conditions. Other conditions lead to chaotic-like kinetic behavior where the rate of alkyl iodide consumption continually changes. Kinetic rate data with CF₃I show that the disappearance rate depends upon both the type of surface and surface preparation. For all three compounds, Arrhenius plots reveal activation energies on the order of 10 kcal/mol, consistent with effective initiation steps of F₂ + RI → RIF + F, where R represents the CF₃, C₂F₅, or n-C₃F₇ radical respectively. The end products of the F₂ + RI reactions are RF, R₂, and IF₅, suggesting that the R radicals play an important kinetic role. Introducing O₂ into the F₂ + RI reaction systems results in successive oxidation of R by O₂, leading to the formation of CF₂O as an additional end product. IF(B → X) emission is observed from the RI-rich F₂ + RI reactions, confirming the existence of IF as an intermediate. © 1996 John Wiley & Sons, Inc.     

Notes on the Asymptotic Linearity Theorems

The present article provides three lemmas that initiate the generalization of the theory of additive correlation involving the Asymptotic Linearity Theorems, which were constructed for a study of the correlation between structure and properties in molecules having many identical moieties. The new tools provided here also help to pave the way to linking the above theory with a theoretical framework developed for the asymptotic analysis of certain chemical kinetic network systems.On leave from: Institute for Fundamental Chemistry, 34-4 Takano-Nishihiraki-cho, Sakyo-ku, Kyoto 606, Japan.     

Certification of the contents of five polychlorodibenzo-p-dioxins (D48, D54, D66, D67, D70), and six polychlorodibenzo-furans (F83, F94, F114, F121, F124, F130) in a fly ash extract (CRM 429)

Summary A fly ash extract was prepared and studied for the homogeneity and the stability (CRM 429) with respect to five polychlorodibenzo-p-dioxins (D48, D54, D66, D67 and D70) and six polychlorodibenzofurans (F83, F94, F114, F121, F124 and F130). The certification exercise is described; the analytical techniques used for the certification and the quality control guidelines that were followed are also given. The difficulties encountered in the determination of F118 are discussed.Abbreviations CI Confidence interval - CV Coefficient of variation - D48 2,3,7,8-T4CDD - D54 1,2,3,7,8-P5DD - D65 1,2,3,4,6,9-H6CDD - D66 1,2,3,4,7,8-H6CDD - D67 1,2,3,6,7,8-H6CDD - D70 1,2,3,7,8,9-H6CDD - ECD Electron capture detector - FID Flame ionization detector - FT Film thickness - F83 2,3,7,8-T4CDF - F89 1,2,3,4,8-P5CDF - F94 1,2,3,7,8-P5CDF - F114 2,3,4,7,8-P5CDF - F118 1,2,3,4,7,8-H6CDF - F119 1,2,3,4,7,9-H6CDF - F121 1,2,3,6,7,8-H6CDF - F124 1,2,3,7,8,9-H6CDF - F127 1,2,4,6,8,9-H6CDF - F130 2,3,4,6,7,8-H6CDF - GC Gas chromatography - HR High resolution (MS) - H6CDD Hexachlorodibenzo-p-dioxin - H6CDF Hexachlorodibenzofuran - H7CDD Heptachlorodibenzo-p-dioxin - H7CDF Heptachlorodibenzofuran - IR Infra Red spectroscopy - IS Internal standard - LR Low resolution (MS) - MS Mass spectrometry - OCDD Octachlorodibenzo-p-dioxin - OCDF Octachlorodibenzofuran - P5CDD Pentachlorodibenzo-p-dioxin - P5CDF Pentachlorodibenzofuran - PCDD Polychlorodibenzo-p-dioxin - PCDF Polychlorodibenzofuran - RSF Relative sensitivity factor - SIM Selected ion monitoring - T4CDD Tetrachlorodibenzo-p-dioxin - T4CDF Tetrachlorodibenzofuran     

Threshold behavior in electron-transfer collisions between rubidium atoms and C2F5Cl or C2F5I molecules

Rubidium atoms are accelerated in a high-temperature expansion of hydrogen to produce beams with energies high enough to observe collisional ionization with a cross beam. The speed of the atoms is directly measured by time-of-flight techniques, and the positive and negative ions produced are detected in separate mass spectrometers and detected in coincidence. Chloroperfluoroethane produces C(2)F(5)(-) and Cl(-) ions, whereas iodoperfluoroethane produces I(-), C(2)F(5)(-), and C(2)F(5)I(-) ions. When the measured speed distributions are used, the signal versus energy may be deconvolved to yield thresholds and electron affinities (EAs). The EA for C(2)F(5)I is measured to be 0.96 +/- 0.1 eV. Anomalously high EA values result for C(2)F(5) apparently because C(2)F(5)(-) is produced by parts per million concentrations of Rb(2).     

2D F/F NOESY for the assignment of NMR spectra of fluorochemicals

Two-dimensional (2D) NMR is an invaluable technique for the complete analysis and assignment of chemical structures. Although ¹⁹F/¹⁹F COSY experiments are routinely used for assignments in perfluorochemicals, interpretation can be difficult because four-bond (⁴J_FF) coupling constants are typically 5-10-fold larger than vicinal (³J_FF) coupling constants. Furthermore, the dependence of long range coupling constants on stereochemistry is not always known. Fluorine-fluorine NOESY correlations represent an enhancement in the arsenal of 2D ¹⁹F NMR experiments. The NOESY and COSY spectra of 2,2,3,3,4,4,4-heptafluorobutanol and a telomeric perfluorochemical iodide show that COSY identifies the 1,4-fluorine interactions whereas NOESY identifies the vicinal fluorine atoms. The combined experiments have been used to unambiguously assign all of the fluorines in a mixture of cis- and trans-perfluoro-1,3-dimethylcyclohexane and in a substituted perfluorotetrahydrofuran.     

Non Linearity of Glassy Polymers

In this paper the source of non linearity in amorphous materials will be analyzed and verified with phenomenological approaches. A series of simulated results, replicating the relevant experimental data presented in literature along the years, will be reported.     

Metal complexes with N-(trifluoromethylbenzyl)iminodiacetate chelators (x-3F ligands). Part I. Copper(II) chelates of p-3F,m-3F,and o-3F with or without imidazole-like ligands

Eight Cu(II) complexes with N-(p-, m- or o-trifluoromethylbenzyl)iminodiacetate chelators (x-3F ligands) have been synthesized to promote C–F/H interligand interactions involving the F₃C-group: {[Cu(μ₂-p-3F)(H₂O)]·3H₂O]}_n (1), [Cu(m-3F)(H₂O)₂] (2), [Cu(p-3F)(Him)(H₂O)] (3), [Cu(m-3F)(Him)(H₂O)] (4), [Cu(o-3F)(Him)(H₂O)] (5), [Cu₂(p-3F)₂(H5Meim)₂(H₂O)₂] (6), [Cu(m-3F)(H5Meim)(H₂O)] (7), and [Cu(o-3F)(H5Meim)(H₂O)] (8) [Him and H5Meim = imidazole and the “remote” tautomer 5-methylimidazole, respectively]. The compounds were studied by single-crystal X-ray diffraction, FT-IR, electronic spectra and coupled thermogravimetric + FT-IR methods. The conformation of the iminodiacetate chelating moiety (IDA group) is fac-NO + O(apical) in 1 and mer-NO₂ in 2–8. The fac-IDA conformation observed in 1 is related to its polymeric structure and the coordination of a O’-carboxylate donor, from an adjacent complex unit, trans to the Cu–N(IDA) bond. The mer-IDA conformation in 2 is in agreement with similar compounds with an aqua ligand trans to the corresponding Cu–N(IDA) bond. As expected, the ternary complexes 3–8 feature a mer-IDA conformation. Some of the studied complexes exhibit disorder in the –CF₃ group and C–H?F interligand interactions along with conventional N–H?O and O–H?O interactions. The thermal decomposition of all studied compounds under air flow produces variable amounts of trifluorotoluene.     

Comment on the reply by M. D. Judd and M. I. Pope

Journal of Thermal Analysis and Calorimetry -     

Tremorgenic indole alkaloids. Studies directed toward the assembly of the A, F, and I rings of penitrem D: observation of an unexpected stereochemical outcome

[formula: see text] In this Letter we demonstrate the viability of a highly stereoselective tandem Mannich cyclization-grammine fragmentation/addition cascade, critical for assembly of the A and F rings of penitrem D. We also explored simultaneous execution of this tactic with concurrent construction of ring I. Reinvestigation of a model system provided an explanation for the unanticipated stereochemical outcome at C(28).     

Measurement of the eddy diffusion term in chromatographic columns. I. Application to the first generation of 4.6mm I.D. monolithic columns

The corrected heights equivalent to a theoretical plate (HETP) of three 4.6mm I.D. monolithic Onyx-C(18) columns (Onyx, Phenomenex, Torrance, CA) of different lengths (2.5, 5, and 10 cm) are reported for retained (toluene, naphthalene) and non-retained (uracil, caffeine) small molecules. The moments of the peak profiles were measured according to the accurate numerical integration method. Correction for the extra-column contributions was systematically applied. The peak parking method was used in order to measure the bulk diffusion coefficients of the sample molecules, their longitudinal diffusion terms, and the eddy diffusion term of the three monolithic columns. The experimental results demonstrate that the maximum efficiency was 60,000 plates/m for retained compounds. The column length has a large impact on the plate height of non-retained species. These observations were unambiguously explained by a large trans-column eddy diffusion term in the van Deemter HETP equation. This large trans-rod eddy diffusion term is due to the combination of a large trans-rod velocity bias (?3%), a small radial dispersion coefficient in silica monolithic columns, and a poorly designed distribution and collection of the sample streamlets at the inlet and outlet of the monolithic rod. Improving the performance of large I.D. monolithic columns will require (1) a detailed knowledge of the actual flow distribution across and along these monolithic rod and (2) the design of appropriate inlet and outlet distributors designed to minimize the nefarious impact of the radial flow heterogeneity on band broadening.     

Chemiluminescence mapping. I. Experimental method and initial measurments on the D+F2 and F+D2 reactions

Measurements by a new experimental chemiluminescence method of the nascent DF product vibrational distribution confirm earlier findings for the F + D₂ → DF(ν?4) + D reaction. The distribution for D + F₂ → DF(ν?15) + F shows a larger fraction (≈ 78%) of the reaction exothermicity channeled into product vibration than is observed by conventional chemiluminescence measurements on the parallel H + F₂ system (58%). The new method, termed chemiluminescence mapping for its simultaneous recording of spectrally and temporally resolved chemiluminescence, differs from the earlier arrested relaxation and measured relaxation techniques by the introduction of a short duty cycle pulsed molecular reagent source, a modified deuterium dissociation source, and signal averaged (time resolved), detection of the DF infrared emission. The chemiluminescence mapping technique results for D + F₂ and F + D₂, are presented; apparent deviation from the energy distribution in the H + F₂ system is discussed.