Microanalysis of perfluoro compounds

Summary Because of the extremely high thermal and chemical stability of perfluoro organic compounds, special methods of analysis are required for carbon, hydrogen and fluorine. Sulfur, phosphorus, and halogens can be determined by conventionalCarius digestion and subsequent gravimetric methods. Nitrogen is determined by theDumas method. Oxygen cannot be determined by the usualUnterzaucher method.Carbon and hydrogen are determined by combustion in oxygen with a tube filling consisting of (Ag; 3 MgO · Al₂O₃; Ag) at 950° C; (Ag; Pb₂O₃) at 450° C; (Ag;PbO₂;Ag) at 180° C. The sample burner is operated at 950° to 1000° C.Fluorine is determined by reaction with sodium in a conventional sodium peroxide bomb with lead or copper gasket. The lower part of the bomb is held at red heat with a torch for about 20 seconds. The sodium fluoride from the reaction is titrated with thorium nitrate.

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Zusammenfassung Für die Bestimmung von Kohlenstoff, Wasserstoff und Fluor in organischen perfluorierten Verbindungen sind wegen deren außerordentlich hoher thermischer und chemischer Stabilität spezielle analytische Methoden notwendig. Schwefel, Phosphor und die Halogene können nachCarius bzw. mit den üblichen gravimetrischen Methoden bestimmt werden. Sauerstoff kann nicht nach derUnterzaucher- Methode bestimmt werden.Kohlenstoff und Wasserstoff sind bestimmbar bei Verbrennung mit einer Rohrfüllung aus (Ag; 3 MgO · Al₂O₃; Ag) bei 900°; (Ag; Pb₂O₃) bei 450°: (Ag; PbO₂; Ag) bei 180°. Der bewegliche Brenner wird auf einer Temperatur von 950° bis 1000° gehalten.Fluor kann durch Umsetzung mit Natrium in einer gewöhnlichen Peroxyd-Bombe mit Blei- oder Kupfer-Dichtung bestimmt werden. Der untere Teil der Bombe wird mit einem Gebläse für 20 Sekunden auf Rotglut erhitzt. Das gebildete Natriumfluorid wird in der gewöhnlichen Weise mit Thoriumnitrat titriert.

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Résumé La grande stabilité thermique et chimique des composés organiques perfluorés impose l'emploi de méthodes spéciales pour le dosage du carbone, de l'hydrogène et du fluor. Il est possible de déterminer le soufre, le phosphore, et les halogènes par digestion classique deCarius suivie d'un dosage gravimétrique approprié. L'azote est dosé par la méthode deDumas; quant à l'oxygène, il ne peut être déterminé par la méthode habituelle deUnterzaucher.Le carbone et l'hydrogène sont déterminés par combustion dans l'oxygène à l'intérieur d'un tube comportant un remplissage constitué par (Ag; 3 MgO · Al₂O₃; Ag) à 950°, (Ag; Pb₂O₃) à 450° (Ag; PbO₂; Ag) à 180° C. Le brûleur mobile permet d'obtenir une température de 950 à 1000° C.Le fluor est dosé après minéralisation par le sodium dans une bombe courante à peroxyde de sodium, comportant un joint de plomb ou de cuivre. La partie inférieure de la bombe est portée au rouge à l'aide d'un chalumeau pendant environ 20 secondes. Le fluorure de sodium obtenu est titré à l'aide de nitrate de thorium.

     

Synthesis of difunctional organooxasilacycloalkanes

2,8-Dichloro-2,4,4,6,6,8,10,10,12,12-decamethyl-5-carbacyclohexasiloxane, 4,7-dichloro-2,2,4,7-tetramethyl-1,3-dioxa-2,4,7-trisilacyclohepatane, and 4,8-dichloro-2, 2,4,8-tetramethyl-1,3-dioxa-2,4,8-trisilacyclooctane were prepared for the first time by heterofunctional condensation of 1,1,7,7-tetrachloro-1,3,3,5,5,7-hexamethyl-4-carbatetrasiloxane with 1,3-dihydroxy-1,1,3,3-tetramethyldisiloxane, of 2,2,5,5-tetrachloro-2,5-disilahexane with dihydroxydimethylsilane, and of 2,2,6,6-tetrachloro-2,6-disilaheptane with dihydroxydimethylsilane, respectively. Hydrolysis of the resulting compounds afforded the corresponding dihydroxy derivatives, andtrans-isomers of some of these derivatives were isolated in individual form. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1436–1441, August, 2000.     

Synthesis of perfluoro(methyl vinyl ether) polymer at high pressures

Polymer of perfluoro(methyl vinyl ether) was synthesized for the first time. Polymerization was carried out at pressures from 300 to 1500 MPa and temperatures from 80 to 200 °C. The polymer synthesized is elastic, transparent, and soluble in perfluorobenzene, perfluorodecalin, and other perfluorinated solvents. The intrinsic viscosity of the polymer reaches 2 dL g^s-1. The study of the thermal stability on a derivatograph showed that the weight loss of the polymer sample occurred at 372 °C, being 0.1%.     

Polyesterification of halogen containing difunctional compounds

The increasing interest in halogen containing polymers has led us to re-evaluate the different methods for the polycondensation of fluorinated and chlorinated monomers to form polyesters. The use of acid chlorides easily gives polymers with relatively high molecular weights (above 3000). We also describe in this work a new method of polytransesterification from the bishydroxyethyl esters of fluorinated and chlorinated diacids at temperatures below 200°C.     

Interaction of anions with perfluoro aromatic compounds

The complexes formed by a variety of anions with perfluoro derivatives of benzene, naphthalene, pyridine, thiophene, and furan have been calculated using DFT (B3LYP/6-31++G**) and MP2 (MP2/6-31++G** and MP2/6-311++G**) ab initio methods. The minimum structures show the anion interacting with the pi-cloud of the aromatic compounds. The interaction energies obtained range between -8 and -19 kcal mol(-1). The results obtained at the MP2/6-31++G** and MP2/6-311++G** levels are similar. However, the B3LYP/6-31++G** results provide longer interaction distances and smaller interaction energies than do the MP2 results. The interaction energies have been partitioned using an electrostatic, polarization, and van der Waals scheme. The AIM analysis of the electron density shows a variety of topologies depending on the aromatic system considered.     

Synthesis of fluorinated difunctional monomers

In order to obtain fluorinated difunctional monomers for fluoropolyurethanes, we synthesized novel fluorinated aliphatic diisocyanates [OCNCH₂(CF_c2)_nCH₂NCO] from corresponding diols [HOCH₂CH₂(CF₂)_nCH₂CH₂OH]. Oxidation of the diols with chromium trioxide-sulfuric acid gave α, α, ω, ω-tetrahydroperfluoroalkylene dicarboxylic acids in high yields. Then treating the acids with phosphorus pentachloride afforded corresponding dicarboxyl chlorides, which are easily converted to dicarboxyl azides with hydrazoic acid-pyridine complex. Finally, on Curtius rearangement of the azides, the end products, α, α, ω, ω-tetrahydroperfluoroalkylene diisocyanates were obtained in 53% (n=4) and 19% (n=6) yields from the starting diols.     

Synthesis and polycondensation of difunctional tetraazacyclododecanes

We have developed a method for getting the tetraazacyclododecane structure into the backbone of a macromolecular chain. Two different reaction processes were investigated: polycondensation from diacid macrocycles using activation of the acid functions by thionyl chloride and polycondensation from diester macrocycles by aminolysis with different aliphatic diamines. Cyclic and linear oligomers have been obtained by polycondensation of 1,7-di(ethylacetate)-4,10-ditosyl-1,4,7,10-tetraazacyclododecane with ethylenediamine and dodecanediamine. In both cases, we managed to get oligomers containing several macrocycle units into their backbone. Furthermore, these results highlighted the classical problem of the competition between cyclisation and macromolecular chain formation encountered during polycondensation reactions.     

The synthesis of perfluoro(alkyletherphenyl) phosphines

The first perfluorophenyl substituted phosphine, C₆F₅)₃P was prepared by Wall et al. [1]. Since then numerous pentafluorophenylphosphorous compounds [2] have been prepared and their properties studied. Substituted perfluorophenylphosphines (R_fC₆F₄)₃P however not been extensively studied. Those that have been reported are all solids: (C₆F₅)₃P, m.p. 116° [1]; (p-CF₃C₆F₄)₃P, m.p. 103-105° [3]; (p-C₈F₁₇C₆F₄)₃P m.p. 117° [3]; and (p-C₆F₅OC₆F₄)₃P, m.p. 135-137° [4].     

Synthesis of perfluoro[2.2]paracyclophane

A synthesis of perfluoro[2.2]paracyclophane has been sought ever since the partially fluorinated octafluoro[2.2]paracyclophane (AF4) was prepared and its chemistry studied. This compound has now been prepared in 39% yield from the precursor, 1,4-bis(chlorodifluoromethyl)-2,3,5,6-tetrafluorobenzene by its reaction with Zn when heated in acetonitrile at 100 degrees C. Two preparations of the precursor, first from 1,4-dicyano-2,3,5,6-tetrachlorobenzene and an improved method beginning from 1,2,4,5-tetrachlorobenzene, are also described as are key comparisons to our related synthesis of AF4.     

Reaction of a 2-aminoindole with difunctional compounds

The reaction of a 2-aminoindole with arylidenemalonic and arylidenecyanoacetic esters was studied. The effect of substituents in the benzene ring of the arylidenemalonic ester on the reaction pathway is demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 899–902, July, 1992.     

Electrochemistry in blood substitutes based on perfluoro compounds

The electrochemical properties of Fluosol 43, an aqueous emulsion of perfluorotri-butylamine used as a blood substitute are reported. A saturated calomel electrode prepared in Fluosol 43 is a suitable reference system. The electroactivity ranges were determined for mercury, silver, platinum, vitreous carbon and boron carbide working electrodes; they are analogous to those observed in water under the same conditions. The diffusion coefficients of some typical cations are smaller in the emulsion than in water. The reduction of dissolved oxygen is discussed; the electrochemical procedures characterize the whole emulsion and not only the aqueous phase.     

EPR study of radiolysis of perfluoro(isobutyl-p-methylcyclohexane)

Conclusions Radiation of perfluoro(isobutyl-p-methylcyclohexane) results in the formation of at least three types of perfluorocarbon radicals that have long lives in the liquid. The extremely low probability of their recombination in the liquid at room temperature may be due to steric shielding of the unpaired electron. The lifetime of the LRs that are formed depends on the radiation dose and temperature.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1260–1263, June, 1988.The authors wish to express their appreciation to K. N. Makarov for assistance in this work.     

Synthesis of difunctional 1,4-dimethyl-1,4-disilacyclohexanes

Transformations of HVinSiCl₂, HVinSi(Me)Cl, HVinSi(Me)Ph, and HVinSi(Me)NEt₂ in the presence of Pt catalyst were studied. In dilute solutions, the reaction gave a mixture of structural and stereoisomers of five- and six-membered disilacyclanes, resulting from intramolecular cyclization of the initially formed linear dimer. In the case of methyl(phenyl)disilacyclane, the structural isomers were separated andtrans-1,4-dimethyl-1,4-diphenyl-1,4-disilacyclohexane was isolated. The reaction of this product with HCl in the presence of AlCl₃ followed by hydrolysis resulted in the synthesis oftrans-1,4-dichloro- andtrans-1,4-dihydroxy-1,4-dimethyl-1,4-disilacyclohexanes. The structures of the structural and stereoisomers synthesized were confirmed by¹H,¹³C, and²⁹Si NMR and IR spectroscopies and mass spectrometry. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1734–1738, September, 1999.     

Synthesis of a difunctional orthogonal coupler for the preparation of carbohydrate-functionalized sP(EO-stat-PO) hydrogels

The synthesis and characterization of a new difunctional coupler (4) based on trimethylolpropane (TMP) are described. The coupler is used to connect biologically active N-acetylglucosamine (GlcNAc) on amino-reactive microtiter plates and on star-shaped poly[(ethylene oxide)-stat-(propylene oxide)] hydrogel layers in microtiter plates. The biological activity of immobilized carbohydrates is determined using an enzyme-linked lectin assay.     

Standard enthalpies of formation of perfluoro(2-methyl-3-oxa)hexanoic and perfluoro(2,5-dimethyl-3,6-dioxa)nonanoic acids

The energies of combustion of perfluoro(2-methyl-3-oxa)hexanoic and perfluoro(2,5-dimethyl-3,6-dioxa)nonanoic acids are for the first time measured in a calorimeter with a rotating platinized bomb and used to calculate the standard enthalpies of formation of these compounds in the liquid state. Based on the enthalpies of formation, the contribution from the [-CF₂OCF(CF₃)-] group to the enthalpies of formation of perfluoro acids is calculated.     

Synthesis of difunctional initiator via the Peterson reaction

This paper presents an improved method to prepare divinylphenyl compounds which are a useful class of precursors in preparing difunctional organolithium initiators. In the past, most of the divinylphenyl compounds reported were prepared from reactions of phosphorus-substituted carbanions with aldehydes and ketones (Wittig reaction). The phosphorus by-product of the Witting reaction was difficult to be completely removed from the final products. In this paper, we apply the Peterson reaction (silane substituted carbanions) to the synthesis of divinylphenyl compounds. This reaction appears to be operationally simpler and cleaner than the Wittig reaction since the by-product of silane is easily removed by silica Gel chromatography. The syn-elimination of β-hydroxylsilane is complete and clean under NaH condition with no detectable isomers in the final product. The reaction of the divinylphenyl compound with S-butylithium forms a difunctional organolithium initiator which is used to prepare triblock copolymers with the desirable microstructure in each block.     

Synthesis and structure of a difunctional siloxane dendron

A difunctional dendron composed of three spiro-linked cyclosiloxane fragments was synthesized by a convergent way. This is of interest for the preparation of cylindrical and spherical dendritic molecules with the inorganic siloxane core and peripheral organic layer. The structures of the dendron synthesized and intermediates containing the Si-Cl, Si-H, Si-OH groups were confirmed by data from mass-spectrometry and X-ray diffraction.