Electron structure and reactivity of organofluorine compounds. 3. Mndo and ami calculations of the ground state of perfluoroalkyl chlorides,bromides, and iodides

The semiempirical quantum chemical MNDO and AMI methods were used to determine the equilibrium geometries and electron properties of molecules of perfluoroalkyl halides (R_FX): CF₃X, CF₃CF₂X, (CF₃)₂CFX, (CF₃)₃CX for X=Cl, Br, and I. It was determined that the effective charge on the Cl atom in R_FCl is negative, positive on the I atom in R_FI, and depends on R_F for the Br atom in R_FBr. The CF₃ group can act as either an electron acceptor or donor in various perfluoroalkyl halides. The strongest C–I bond in the perfluoroalkyl halides occurs with a tertiary RF group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1059–1063, May, 1990.     

Gas chromatography of saturated fluorinated carboxylic acid esters. 3. Temperature effect on gas chromatographic parameters

In six homologous (R_FC(O)O(CH₂)_mCH₃, m=0–5) and six pseudohomologous (CF₃-(CF₂)_nC(O)OR, n=0–5) of saturated, fluorinated carboxylic acid esters the effect of analysis temperature (T_a) in the range 60–160°C on the values of retention indexes (I) and on the differential molar free energy, enthalpy, and entropy of sorption of methylene and difluoromethylene groups when using SE-30 and SKTFT-50Kh as the stationary phase (SP) was studied. For each homolog I decreases linearly as T_a increases, but the values of dI/dT_a are different for different homologs and increase as the length of the fluorinated chain increases. The sorption parameters H_m (CH₂) and S_m(CH₂) are constant when m > 3 and H_n (CF₂) and S_n(CF₂) vary regularly as n varies. The values of H_m (CH₂) and S_m (CH₂) exceed those of the corresponding H_n (CF₂) and S_n (CF₂) for m=n when adsorbed on both SPs. The thermodynamic sorption parameters of the esters for m=1 and n=1 differ sharply from the corresponding parameters for m > 2 and n > 2.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1487–1493, July, 1991.     

X-ray diffraction (powder), e.s.r. and other spectral studies oftris[methylenebis(diphenylphosphine oxide)]iron(III) perchlorate

Summary Bifunctional methylenebis(diphenylphosphine oxide) (mdpo) on reaction with iron(III) perchlorate forms the complex, [Fe(mdpo)₃](ClO₄)₃ · H₂O. This has been characterized through elemental analysis, i.r., far-i.r., u.v. and visible spectroscopy and by x-ray diffraction, magnetic moment, molar conductance and e.s.r. data. The e.s.r. spectrum consists of five lines with transitions from: ¦–5/2¦–3/2¦–3/2¦–1/2, ¦–1/2¦+1/2¦+1/2¦+3/2 and ¦+3/2¦+5/2 centred at a g-value of 2.00. On the basis of these studies, a chelated octahedral structure has been assigned to the cation, [Fe(mdpo)₃]³⁺.     

Copper(II) halide reactions with the - NH · CS - group in heterocyclic pentaatomic rings

Summary White crystalline complexes of general formula Cu₂L₄X₂ (where X = Cl, Br and L = 1, 3-oxazolidine-2-thione, pyrrolidine-2-thione,N-methyl-1,3-imidazolidine-2-thione andN-ethyl-1,3-imidazolidine-2-thione) and CuLX (where L = 1,3-imidazolidine-2-thione) were prepared by reduction of copper(II) halides and studied by i.r. spectroscopy in the 4000–200 cm^– range. Evidence for ligand coordination to the metal through sulphur was found in each case. The(CuCI) vibration in all the chloro derivatives falls atca. 240 cm^–.     

Reasons for Selective C–C Bond Rupture upon Photodegradation of the Long-Lived Perfluoro-2,4-dimethyl-3-ethylpentyl-3 Radical

A difference in the mechanisms of photoinduced and thermal decomposition of [(CF₃)₂CF]₂C · C₂F₅ radical was demonstrated on the basis of comparison of experimental results and quantum-chemical calculation data. Irradiation with light of < 320 nm resulted in transition of the radical to an excited state followed by the rupture of the CF₂–CF₃ bond having the greatest length in the ground state. In the thermal degradation of this radical (heating up to 373 K), the rupture >CF–CF₃ bonds is more favorable because of low activation barriers for the process (42–54 kJ/mol). The CF₂–CF₃ bond rupture during thermolysis is unlikely, since the corresponding activation barrier is as high as 84–109 kJ/mol.     

Polar addition of perfluoro-tert-hexyl iodide to alkenes and alkynes

The effective charges on the atoms in molecules of perfluoroalkyl halides of general formula (CF₃)_nCF_3–nX (X=Cl, Br, I) have been calculated by the AM1 semiempirical method. In polar solvents perfluoro-tert-hexyl iodide is reduced under the action of alkenes and aromatic hydrocarbons to form 2-hydroperfluoro-2-methyl-pentane and perfluoro-2-methyl-2-pentene. In ethyl acetate the regio- and stereo-specific addition of perfluoro-tert-hexyl iodide to alkenes, butadiene, and alkynes takes place, which is associated with the realization of a polar ion-radical mechanism for the reaction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2057–2061, September, 1989.     

Direct and indirect electrochemical reduction of organic halides in aprotic media

Cyclic voltammetric reduction of 17 different organic halides including alkyl, allyl, and benzyl chlorides, bromides, and iodides in aprotic media (DMF, DMSO, and acetonitrile, AN), containing 0.1 M Bu₄NClO₄, have been reported at glassy carbon (gc) and graphite as working electrodes. A single two-electron irreversible and diffusion-limited reduction of the carbon-halogen bond is observed, the reduction potentials ranging from –1.20 to –2.70 V (versus silver wire quasireference electrode) depending on the halide, the solvent, and the electrode. Indirect reduction of these 17 halides, however, is effected at much lower potentials (–0.79 to –0.92 V versus SCE) depending on the experimental conditions by in situ electrogenerated superoxide ion (O ₂ ^– ) by CPE. The products have been characterized by TLC, GC, CV, or chemical estimation. The diorganic peroxide and the organic hydroperoxide were the major products. In case of tertiary alkyl halides, however, alkenes predominated, due to basic nature of O ₂ ^– in these reactions. These studies indicate sufficient strength of O ₂ ^– as a nucleophile or base depending on the experimental conditions.From Elektrokhimiya, Vol. 41, No. 3, 2005, pp. 350–355.Original English Text Copyright © 2005 by Vasudevan.This article was submitted by the author in English.     

Thermally induced isomerisation and decomposition of diethylenetriamine complexes of nickel(II) in the solid state

Summary Complexes [NiL₂]X₂·nH₂O (L=diethylenetriamine; n=O when X=CF₃CO₂ or CCl₃CO₂; n=1 when X=Cl or Br, and n=3 when X=0.5SO₄ or 0.5SeO₄) and NiLX₂·nH₂O (n=1 when X=Cl or Br; n=3 when X=0.5SO₄ or 0.5SeO₄) have been synthesised and investigated thermally in the solid state. NiLSO₄ was synthesised pyrolytically in the solid state from [NiL₂]SO₄·[NiL₂]X₂ (X=Cl or Br) undergo exothermic irreversible phase transitions (242–282° C and 207–228° C; H=–11.3 kJ mol^–1 and –1.9 kJ mol^–1 for [NiL₂]Cl₂ and [NiL₂]Br₂, respectively). [NiL₂]-phenomenon (158–185° C; H=2.0 kJ mol^–1). NiLX₂· nH₂O (n=1 or 3) undergo simultaneous deaquation-isomerisation upon heating. All the complexes possess octahedral geometry.     

Conductance behavior of 1∶1 electrolytes in N,N-dimethylmethanesulfonamide

The conductances of eleven 1:1 salts have been measured at 50°C in N,N-dimethylmethanesulfonamide (DMMSA) for electrolyte concentrations of 1.2–55.0×10^–4 mol-dm^–3. The conductance data were analyzed using the equation of Lee and Wheaton. Calculations for different values of the distance parameter R indicate that all salts studied are only slightly associated in DMMSA. Association was somewhat greater for the trimethylphenylammonium halides than for the tetraalkylammonium salts. Ionic limiting molar conductances were estimated using the tris (isopentyl) butylammonium tetraphenylborate approximation. The markedly smaller value for _o (Na⁺) compared to the values for _o (Br^–) and _o (I^–) indicates that the sodium ion is probably more extensively solvated than the halide ion. In general, it appears that DMMSA (dielectric constant=80.31 at 50°C) is similar in its solvent properties to dipolar aprotic heterocyclic solvents such as 2-cyanopyridine and 3-methyl-2-oxazolidone which have similar dielectric constants.     

Catalytic phosphorylation of polyfluoroalkanols. 15. Catalytic phosphorylation of α-polyfluoroalkylbenzyl alcohols by bis(polyfluoroalkyl) chlorophosphates

The catalytic phosphorylation of -polyfluoroalkylbenzyl alcohols by bis(polyfluoroalkyl) chlorophosphates is a convenient method for the synthesis of various bis(polyfluoroalkyl)(-polyfluoroalkylbenzyl) phosphates, including those having donor substituents in the benzene ring. It was shown that in the series of p-methyl--trifluoromethylbenzyl phosphates p-CH₃C₆H₄CH-(CF₃)OP(O)XY (where X, Y=Cl, CF₃CH₂O), the ability to act as O-alkylating agents with respect to polyfluorinated alcohols is a common characteristic, and the alkylating ability increases symbatically with increase in the overall electron-acceptor strength of the X and Y substituents at the phosphorus atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 878–886, April, 1990.     

Synthesis of Boron–Nitrogen–Phosphorus Compounds from N-Silylphosphoranimines

Two modes of reactivity of N-silylphosphoranimines have been utilized to prepare the title compounds containing either B–N=P or Si–N=P–N–B linkages. First, silicon-nitrogen bond cleavage reactions of the N-silylphosphoranimines, Me₃SiN=PMe(R)OCH₂CF₃ (1: R=Me, 2: R=Ph), with various chloroboranes gave the new N-borylphosphoranimines, Ph(Me₂N)B–N=PMe₂OCH₂CF₃ (2) and [(Me₃Si)₂N](Cl)B–N=PMe₂OCH₂CF₃ (10). In other cases, however, the expected B–N=P products were unstable and cyclic phosphazenes [Me(R)P=N]_3,4 were obtained. Second, deprotonation-substitution reactions of the aminophosphoranimines, Me₃SiN=P(R)Me–N(R)H, were used to prepare a series of novel (borylamino)-phosphoranimines, Me₃SiN=P(R)(Me)–N(R)–B(NMe₂)₂ (18: R=Me, R=t-Bu; 19: R=R=Me; 20: R=Ph, R=t-Bu; 21: R=Ph, R=Me) and Me₃SiN=PMe₂–N(t-Bu)–B(Ph)X (22: X=NMe₂, 23: X=OCH₂CF₃). All of the new boron–nitrogen–phosphorus products were fully characterized by multinuclear NMR (¹H, ¹³C, and ³¹P) spectroscopy and elemental analysis.     

MD Simulation of an Infinitely Dilute Aqueous Solution of Formamide. Study of Thermodynamic, Structural, Dynamic, and Spectroscopic Properties

A molecular dynamics simulation of an infinitely dilute aqueous solution of formamide was carried out using an MP2-CP ab initio potential to describe the solute–solvent interaction. Various static and dynamic properties were calculated using this potential obtained by fitting the formamide–water interaction energies to a 12-6-1 type function. These energies were calculated with the supermolecular approach by considering the MP2 correlation and the CP superposition. The values presented for the thermodynamic functions (H _S–W = –25.5 kcal-mol^–1 and G _S–W = –15.9 kcal-mol^–1), the structure of the first hydration layer (with 5 to 6 solvent molecules bonded to the solute), the solute's translational (D= 1.50 × 10^–5 cm²-s^–1) and rotational ( = 6.6 ps) mobility in the surrounding medium, and the positions of the H···O hydrogen bond spectral bands corresponding to these motions (_i = 92, 246, 379, and 636 cm^–1), are in agreement with the available results for this and other similar systems. In addition, the results are compared with those obtained by using parameters transferred from other systems. We observed that these values depend strongly on the potential used and concluded that it is advisable to avoid the use of such parameters.     

Solid state thermal isomerisation of diethylenetriamine complexes of NiX2 (X=NO3, ClO4, BF4 and CF3SO3)

Summary [Ni(dien)₂]X₂·nH₂O (dien=diethylenetriamine; n=0, X=NO₃ or CF₃SO₃; n=0.5, X=ClO₄ or BF₄ and n=2, X=CF₃SO₃) complexes have been prepared and investigated thermally in the solid state. [Ni(dien)₂](NO₃)₂ (1) and [Ni(dien)₂](CF₃SO₃)₂ (2) undergo endothermic irreversible phase transitions (209–247°C and 184–205°C; H=5.6 kJ mol^–1 and 7.7 kJ mol^–1 for (1) and (2), respectively). [Ni(dien)₂](ClO₄)₂·0.5H₂O (3) shows an endothermic irreversible phase transition after deaquation (201–216°C; H=7.7 kJ mol^–1). [Ni(dien)₂](BF₄)₂·0.5H₂O also shows an endothermic irreversible phase transition after deaquation, accompanied by partial decomposition. All the complexes possess octahedral geometry with the ligands arranged meridionally. The phase transitions are explained in terms of conformational changes of the triamine chelate rings.Author to whom all correspondence should be directed. Supplementary data available: i.r. spectra (Table 4) and x-ray diffraction patterns (Table 5).     

New water-soluble and film-forming aminocellulose tosylates as enzyme support matrices with Cu<Superscript>2+</Superscript>-chelating properties

Within the framework of our studies on enzyme-compatible support matrix structures, we succeeded in making further derivatives of the new aminocellulose type P–CH₂–NH–(X)–NH₂ (P = cellulose); (X) = –(CH₂)₂– (EDA), –(CH₂)₂–NH–(CH₂)₂– (DETA), –(CH₂)₃–NH–(CH₂)₃– (DPTA), –(CH₂)₂–NH–(CH₂)₂–NH–(CH₂)₂– (TETA) accessible by nucleophilic substitution reaction with ethylenediamine (EDA) and selected oligoamines starting from 6(2)-O-tosylcellulose tosylate (DS_tosylate = 0.8). The ¹³C-NMR data show that the EDA and oligoamine residues are at C6 of the anhydroglucose unit (AGU) and that OH and tosylate are also (partially) present at C6. OH and partially tosylate are at C2/C3. All the synthesized aminocellulose tosylates were soluble in water and formed transparent films from their solutions. The aminocellulose tosylate solutions and the films prepared from them formed blue-coloured chelate complexes with Cu²⁺ ions, whose absorption maxima at wavelengths in the VIS region were located similarly to those of the Cu²⁺ chelate complexes with EDA and with the oligoamines. AFM investigations have shown that the aminocellulose films, depending on structural and environment-induced factors influencing e.g. SiO₂ polymer films, exhibit flat topographies (<1 nm), and on protonated NH₂ polymer films, such as aminopropyl-functionalized polysiloxane films, nanostructured topographies of derivative-dependent shape and nanostructure size as film supports in the form of nanotubes. The aminocellulose films could be covalently coupled with glucose oxidase enzyme by various known and novel bifunctional reactions via NH₂-reactive compounds. In this connection, it was confirmed again that the immobilized enzyme parameters, such as enzyme activity/area and K_M value, can be changed by the interplay of aminocellulose film, coupling structure and enzyme protein in the sense of an application-relevant optimization.     

Investigation of the structure and reactivity of the stable perfluorodiisopropylethylmethyl radical by ESR and molecular mechanics

The hyperfine coupling (HFC) constants of the unpaired electron with the fluorine nuclei in the stable radical [(CF₃)₂CF]₂CF₂CF₃ (II) were determined by ESR. The stable conformation and the barriers to rotation of the substituents in this radical were calculated by molecular mechanics. The results were consistent with the ESR data. The kinetics of the destruction of the radical (II) were investigated, and the kinetic parameters of the dissociation were determined (k₁₄₀=4.6·10^–4 sec^–1, E_act=30±5 kcal/mole). The disappearance of the radical (II) is accompanied by the accumulation of the new radical (CF₃)₂CF(CF₃)CF(CF₃)CF₂CF₃ (IV), which was studied by ESR. Heating of (II) in the presence of electron donors leads to the partly reversible reduction of the radical (II).Translated from Izvestiva Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1507–1512, July, 1991.     

Silver(I) complexes ofN-ethylthiourea. An infrared study

Summary The following silver(I) complexes ofN-ethylthiourea, L, have been isolated in the solid state: AgLX (X = Cl, Br, ClO₄, BF₄, and CF₃CO₂), Ag₂L₃X₂ (X=ClO₄, BF₄ and CF₃CO₂), AgL₂ClO₄, AgL₃X (X = Cl, Br, I, ClO₄, BF₄ and CF₃CO₂). The decrease of the(CS) and (SCN₂) frequencies in the i.r. spectra of the complexes indicates S-coordination of the ligands. The(AgS) frequencies lie in the 267–252 cm^–1 range for terminal and 240-210 cm^–1 range for bridged or long Ag-S bonds. The following structures may be proposed for the complexes. AgLX (X = Cl and Br), polymeric trigonal coordination with bridging halide ions; Ag₂L₃A₂ (A = ClO₄ and BF₄), polymeric trigonal coordination with three bridging sulphur atoms; AgL₂ClO₄, polymeric tetrahedral coordination with four bridging sulphur atoms; AgL₃A (A = ClO₄ and BF₄), dimeric tetrahedral coordination with two terminal and two bridging sulphur atoms; AgLO₂CCF₃ and Ag₂L₃(O₂CCF₃)₂, trigonal and/or tetrahedral coordination with terminal sulphur bonds and bridging CO₂ groups; AgL₃O₂CCF₃, tetrahedral coordination with terminal sulphur bonds and a monodentate CO₂ group. In the trifluoroacetato complexes, a(AgO) band is observed at 185–209 cm^–1. The AgL₃X complexes (X = Cl, Br and I) show two(AgX) and two(AgS) bands with rather low frequencies corresponding to long metal-ligand bond distances.     

Atranes

The infrared absorption spectra over the range 400–1700 cm^–1 of ten organyl- and organoxysilatranes, p-CH₃C₆H₄O] are investigated. The SiN coordinate link in these compounds is largely unreflected in the fundamental vibration frequencies of the bonds of the central silicon atom or the internal vibration frequencies of the substituents X linked to that atom. However, all the IR spectra have an absorption band in the 570 cm^–1 region, related to the valence vibrations (SiN), or manifesting itself as the frequency (Si-O) of the XSi (O)₃ group, substantially lowered because of interaction between the Si-O and Si-N bonds. Evidence in favor of this bond is shift of the (Si-H) frequency in the spectrum of silatrane(X=H).For Part V see [1].     

Disordered Crystal Structures of Three Halogenated Propionamides CF3CFXCONH2 (X = Cl, Br, I)

The disordered crystal structures of three halogenated propionamides of the general formula CF₃CFXCONH₂, X = Cl (I), Br (II), and I (III), were studied by X-ray diffraction (CAD-4 automatic diffractometer, MoK ). All these structures are monoclinic with space group P2 _1/c . The structures were solved by direct methods and refined by the full-matrix least-squares procedure anisotropically for nonhydrogen atoms. It was established that structures II and III is isomorphic to each other, whereas structure I is not isomorphic to them, although it has a similar molecular packing. The same crystallographic position is statistically (with different probabilities) occupied by two identical molecules (I, II, or III) with different configurations, which may be regarded as one disordered molecule where two substituents at the C₂ atom (halogen X atom and CF₃ group) are mutually statistically interchangeable in the space of the unit cell. The amide fragment (–CONH₂) of these disordered molecules is practically ordered. The crystal structures of I, II, and III have a developed system of intermolecular H-bonds of N–H O type and unusual intramolecular H-bonds of N–H F–C type.     

Cardiac glycosides of theCheiranthus allioni. XII

The seeds ofCheiranthus allioni hort. have yielded three new cardenolides the structures of which have been established and which have been named as 4-dehydrosarmentogenin (II), 4-dehydrosarmentogenin rhamnoside (I), and 4-dehydrosarmentogenin rhamnoglucoside (IV). (II) — C₂₃H₃₂O₅. m.p. 296–302°, [] _D ²⁰ +26.2±3° (in pyridine) is 3,11,14-trihydroxy-14-card-4,20(22)-dienolide. (I) C₂₉-H₄₂O₉, m.p. 268–275°, [] _D ²⁰ –38.2±3° (chloroform-ethanol) is 11,14-dihydroxy-3--L-rhamnopyranosyloxy-14-card-4,20(22)-dienolide.(IV) C₃₅H₅₂O₁₄, [] _D ^20D –44.1±3° (methanol), is 3-(4-O--D-glucopyranosyl--L-rhamnopyranosyloxy)-14-card-4, 20(22)-dienolide. An independent synthesis of 4-dehydrosarmentogenin (II) has been carried out, starting from 3,5,11,14-tetrahydroxy-5,14-card-20(22)-enolide, which has confirmed its structure.For Communication XI, see [1].All-Union Scientific-Research Drug Institute, Kharkov. Kharkov State Pharmaceutical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 119–125, January–February, 1987.     

Electrophilic condensation of 1-hydroperfluoropropylene and 1-hydroperfluoro-1-butene with fluoroethylenes

Conclusions 1-Hydroperfluoropropylene reacts with tetrafluoroethylene in the presence of SbF₅ to form the corresponding 11 and 12 adduct olefins. The condensation is accomplished at both the CFH and CF₂ groups of the starting propylene. Under analogous conditions, 1-hydroperfluoro-1-butene condenses with fluoroethylenes exclusively at the CFH group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1591–1594, July, 1982.