Unsaturated Fluorocarbons Research Articles

Pyrolysis and laser ablation of plasma-polymerized fluorocarbon films: Effects of gold particles

Plasma-polymerized fluorocarbon (PPFC) films were analyzed by thermogravimetric analysis (TGA), direct pyrolysis/mass spectrometry, and laser-ablation/electron-impact mass spectrometry. Fourier transform mass spectrometry was used to detect products. The films were made by plasma polymerizing tetrafluoroethylene in an argon plasma. Two types of films were studied: with and without fine gold particles incorporated in the PPFC films. TGA showed that gold-containing films decompose more rapidly and at lower temperature with increasing gold content. Pyrolysis products were determined as a function of temperature. The predominant positive product ions, using 20 eV electron-impact ionization, were C2F4+, CF3+ and a distribution of higher-mass unsaturated fluorocarbon species, CnFm+, up to at least n=14 and m≥n+1. The predominant negative ions, formed by electron attachment, were also unsaturated fluorocarbon ions which extended up to 1145 u in mass. These species are different from those observed from polytetrafluoroethylene pyrolysis. No dependence of the positive-ion mass spectral distributions of pyrolysis products on gold content of the films was observed. However, the negative-ion pyrograms had a dramatically different temperature dependence for films with and without gold. The results imply that the gold-containing films have regions of lower molecular weight, and a possible formation mechanism is suggested. Laser ablation formed low-mass neutral fluorocarbon species. Ablation of the gold-containing film under direct laser ionization conditions (higher laser power), produced a spectrum resembling the pyrolysis spectrum, suggesting that the gold particles affect the mechanism of the ablation.

X-ray photoelectron and mass spectroscopic study of electron irradiation and thermal stability of polytetrafluoroethylene

Polytetrafluoroethylene (PTFE) was subjected to 3 keV electron bombardment and then heated in vacuum to 300 °C. The behavior of the material as a function of radiation dose and temperature was studied by x-ray photoelectron spectroscopy (XPS) of the surface and mass spectroscopy of the species evolved. A quantitative comparison of the radiation dose rate with that in other reported studies showed that, for a given total dose, the damage observed by XPS is greater for higher dose rates. Lightly damaged material heated to 300 °C evolved saturated fluorocarbon species, whereas unsaturated fluorocarbon species evolved from heavily damaged material. After heating the heavily damaged material, those features in the XPS that were associated with damage diminished, giving the appearance that the radiation damage annealed. The observations were interpreted by incorporating mass transport of severed chain fragments and thermal decomposition of severely damaged material into the branched and cross-linked network model of irradiated PTFE. The apparent annealing of the radiation damage was due to covering of the network by saturated fragments that easily diffused through the decomposed material to the surface region upon heating.

ChemInform Abstract: Pentafluorotellurium Oxide Derivatives of Fluorocarbons.

AbstractReaction of xenon bis(pentafluorotellurium oxide) (I) with unsaturated fluorocarbons gives the appropriate addition products.

Pentafluorotelluriumoxide derivatives of fluorocarbons

The reaction of xenon bis-pentafluorotelluriumoxide, Xe(OTeF 5) 2, with an excess of perfluorobutadiene gives almost exclusively TeF 5OCF 2CFCFCF 2OTeF 5 and only very little TeF 5OCF 2CF(OTeF 5)CFCF 2, the first examples of TeF 5O- substituted unsaturated fluorocarbons. A similar reaction of perfluorocyclohexene produces, depending on the reaction temperature, exclusively the addition product, c-C 6F 10(OTeF 5) 2, or predominantly c-C 6F 11OTeF 5, the mixed addition, fluorination product. In the case of TeF 5OF, an ambient temperature reaction with perfluorobenzene results, depending on the stoichiometry of the reaction, in the addition of either one TeF 5OF or two molecules of TeF 5OF accompanied by the oxygenation of the ring to a cyclohexanone derivative.

Syntheses and reactions of some fluorinated dienes, cyclobutenes and furans

Abstract There are many reports 1 of the pyrolysis of fluorinated organic compounds, including the defluorination of cyclic fluorocarbons over iron to give aromatic compounds. Extending this technique we have investigated the flow pyrolysis of some readily accessible unsaturated fluorocarbons, such as I, II, and III, and found these to be synthetically useful routes to fluorinated dienes, cyclobutenes, and furans. Pyrolyses were carried out using a nitrogen flow over platinum, iron or caesium fluoride heated at 430–700°. The various products can all be rationalized in terms of intermediate allylic radicals, and the solid substrate influences which allylic radicals are formed. We are also investigating the chemistry of those now accessible compounds, such as IV, V, and VI, and some of the preliminary results are described. For example the fluoride ion induced dimerisation of IV gave two major products VII and VIII via a particular interesting mechanism.

Mechanisms of radical production in radiofrequency discharges of CF3Cl, CF3Br, and certain other plasma etchants: Spectrum of a transient species

Radiofrequency discharges in CF3Cl, CF3Br, and C2F6 emit a broad continuum centered at ∼614 nm. The variation of emission intensity with residence time, oxygen additions, power and pressure are evidence that this continuum originates from a common excited species produced by electron impact dissociation of the halocarbon feed gases. The hypothesis that this species is an excited state of the CF3 radical, which undergoes a transition to a repulsive state to yield CF2+F, is consistent with the spectral evidence and explains the presence of CF2 and unsaturated fluorocarbons in these discharges.

Infrared absorption intensities of formyl fluoride

The i.r. absorption intensities of gaseous HCOF and DCOF have been measured under high pressure. The intensity analysis has been carried out, and the derivatives of molecular dipole-moment with respect to a bond stretching or a valence angle deformation have been determined as intensity vectors by the least squares method. Assuming the directions of intensity vectors are those calculated by the CNDO/2 or INDO method, their magnitudes have been determined as follows: a CH = − 0.22, a CO = − 2.90 and a CF = − 5.02( D/Å). Above values are close to those of intensity vectors of unsaturated fluorocarbons. The effect of π electrons on the intensity vectors is briefly discussed.

Shake up phenomena in some unsaturated fluorocarbons

Shake up processes accompanying core ionizations for some simple unsaturated fluorocarbon systems have been studied experimentally by ESCA. Comparison has been made of shake up intensities with those calculated theoretically within the sudden approximation using the equivalent cores concept and the INDO SCF MO formalism. The observed transitions are identified as arising from π*←π excitation accompanying core ionizations and the theoretical calculations give a good overall account of the transition probabilities.

Reactivity reactions of SiMn, GeMn, and SnMn bonds with unsaturated fluorocarbons

The reactions of (CH 3) 3SiMn(CO) 5 with C 2F 4, C 2F 3H, and C 3F 6 and of (CH 3) 3MMn(CO) 5 (MSi or Ge) with perfluorocyclobutene, perfluoro-2-butyne and 3,3,3-trifluoropropyne are described. The new compounds which are formed are either the products of insertion into the MMn bond, or compounds formed by the decomposition of such insertion products.

The role of fluorocarbons in oxidative-addition and -elimination reactions

This lecture describes a comprehensive study of the reactions of unsaturated fluorocarbons with zero-valent complexes of nickel, palladium and platinum. Many stable complexes L2M(AB), where A:B = CF2:CFX LX = F, Cl, CF3 etc], (CF3)2C:O and (CF3)2C:NR [R = H or Me]. have been prepared, as well as five-membered ring complexes L2]\fA.BAn. The various factors which determine the nature of the products are discussed, and it is shown that several of the five-membered ring complexes are formed from the adducts II L,M•A•B. The formation of azine metal complexes from (CF3)2CN2 is also described, INTRODUCTION In 1960, at Harvard University, my research group discovered several methods for synthesizing fluorocarbon—transition metal complexes These included some reactions in which metal ions with a d8-configuration are formally oxidized by a fluorocarbon. viz. Fe(CO)5 + C2F51 -÷ Fe(CO)4(C2F5)I + CO d8 (Fe°) d6 (Fe) Co(CO)2(ir-C5H5) + 2CF2 CF2 oCF2(CF2)2F2(ic-C5H5)(CO) + CO d8 d6 (Co') These syntheses are now known to be examples of a widespread class of reaction in which the metal's oxidation state and coordination number are both increased as a result of interaction with a substrate molecule5' In this context reactions of Vaska's7 iridium(i) complex, Ir(PPh3)2(CO)Cl, have been intensively studied, the term oxidative—addition being used to describe the over-a]] processes given in Scheme 1. Two types of product may be recognized according to whether in the reaction with a substrate molecule AB the reactant has been cleaved into two fragments forming distinct Ir—A and Jr—B bonds, or whether the reactant merely complexes with the iridium ion to form an adduct with a three-centre interaction Ir(AB). In the former case the coordination number of the metal has clearly changed from four to six so that it is no longer coordinatively unsaturated and its oxidation number has increased from +1 to + III, following the accepted convention6. In the latter case, a bond, albeit modified in character compared with that in

The ultraviolet and photoelectron spectra of some unsaturated fluorocarbon derivatives

The ultraviolet spectra and ionization potentials (by photoelectronspectroscopy) of some unsaturated amines, phosphines and stibines are reported.

Stereochemical aspects of nucleophilic substitution at unsaturated fluorocarbon

Stereochemical aspects of nucleophilic substitution at unsaturated fluorocarbon