Reaction of CF3 radicals with CO and O2. Isolation of bis(trifluoromethyl)peroxydicarbonate,CF3OC(O)OOC(O)OCF3, and identification of bis(trifluoromethyl)trioxydicarbonate,CF3OC(O)OOOC(O)OCF3

The synthesis of CF3OC(O)OOCF3, CF3OC(O)OOC(O)OCF3, and CF3OC(O)OOOC(O)OCF3 is accomplished by the photolysis of a mixture of (CF3CO)2O, CO, and O2. Pure CF3OC(O)OOCF3 and CF3OC(O)OOC(O)OCF3 are isolated after thermal decomposition of CF3OC(O)OOOC(O)OCF3 and repeated trap-to-trap condensation. Additional spectroscopic data of known CF3OC(O)OOCF3 are obtained by recording NMR, IR, Raman, and UV spectra: At room temperature CF3OC(O)OOC(O)OCF3 is stable for days in the liquid or gaseous state. The melting point is -38 degrees C, and the boiling point is extrapolated to 73 degrees C from the vapor pressure curve log p = 8.657-1958/T (p/mbar, T/K). The new compound is characterized by molecular mass determination and by NMR, vibrational, and UV spectroscopy. The new trioxide CF3OC(O)OOOC(O)OCF3 cannot be separated from CF3-OC(O)OOC(O)OCF3 by distillation due to their similar boiling points. CF3OC(O)OOOC(O)OCF3 decomposes at room temperature within hours into a mixture of CF3OC(O)OOC(O)OCF3, CF3OC(O)OOCF3, CO2, and O2. Its characterization is discussed along with a possible mechanism for formation and decomposition reactions.     

Difluorophosphoryl Nitrene F2P(O)N: Matrix Isolation and Unexpected Rearrangement to F2PNO

Triplet difluorophosphoryl nitrene F₂P(O)N (X³A′′) was generated on ArF excimer laser irradiation (λ=193 nm) of F₂P(O)N₃ in solid argon matrix at 16 K, and characterized by its matrix IR, UV/Vis, and EPR spectra, in combination with DFT and CBS‐QB3 calculations. On visible light irradiation (λ>420 nm) at 16 K F₂P(O)N reacts with molecular nitrogen and some of the azide is regenerated. UV irradiation (λ=255 nm) of F₂P(O)N (X³A′′) induced a Curtius‐type rearrangement, but instead of a 1,3‐fluorine shift, nitrogen migration to give F₂PON is proposed to be the first step of the photoisomerization of F₂P(O)N into F₂PNO (difluoronitrosophosphine). Formation of novel F₂PNO was confirmed with ¹⁵N‐ and ¹⁸O‐enriched isotopomers by IR spectroscopy and DFT calculations. Theoretical calculations predict a rather long P? N bond of 1.922 Å [B3LYP/6‐311+G(3df)] and low bond‐dissociation energy of 76.3 kJ mol^?1 (CBS‐QB3) for F₂PNO.     

Molecular structure, spectroscopy and matrix photochemistry of fluorocarbonyl iodide, FC(O)I

The molecular structure of FC(O)I has been determined by gas electron diffraction. High-level ab initio methods, including coupled-cluster and the new correlation-consistent basis sets for fourth row elements, have been used to calculate the structure of FC(O)I. A comprehensive vibrational spectroscopic study (both IR and Raman) complemented by high-level calculations has also been performed. Furthermore, UV, mass, and NMR spectra have been recorded for FC(O)I. The matrix photochemistry of FC(O)I has been studied with a low-pressure mercury lamp and with a high-pressure xenon lamp in combination with interference and cut-off filters. UV photolysis revealed the formation of the OC. IF and OC.FI complexes and further photolysis of these complexes at lambda>320 nm resulted in a re-formation of FC(O)I. The structural conformation of the complexes has been characterized by comparing shifts in their CO and IF vibrational modes with respect to those of the free species. The structures, vibrational properties, and stability of the complexes were analyzed with the aid of coupled-cluster ab initio calculations.     

Kinetics of the thermal decomposition of bis(trifluoromethyl) peroxydicarbonate,CF3OC(O)OOC(O)OCF3

Thermal decomposition of bis(trifluoromethyl) peroxydicarbonate has been studied. The mechanism of decomposition is a simple bond fission, homogeneous first‐order process when the reaction is carried out in the presence of inert gases such as N₂ or CO. An activation energy of 28.5 kcal mol^?1 was determined for the temperature range of 50–90°C. Decomposition is accelerated by nitric oxide because of a chemical attack on the peroxide forming substances different from those formed with N₂ or CO. An interpretation on the influence of the substituents in different peroxides on the O? O bond is given. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 15–19, 2003     

Early barriers in the matrix photochemical formation of syn-anti randomized FC(O)SeF from the OCSe:F(2) complex

The photochemically induced reaction of OCSe and F(2), isolated together in an Ar matrix at about 15 K, leads to formation of the hitherto-unknown fluorocarbonylselenyl fluoride FC(O)SeF. The reaction occurs via a van der Waals complex O=C=Se...F-F that favors very early formation of the anti conformer. The presence and subsequent decay of a band assigned to the F-F vibration correlated with perturbed OCSe bands seems to confirm this hypothesis. Subsequent irradiation of the matrix leads to randomized FC(O)SeF by a photochemically induced conformational equilibrium between syn and anti forms. Another photochemical reaction channel is the formation of CO and SeF(2) molecules, which are produced in the same matrix cage and then form a loose complex. The changes were monitored and the products characterized experimentally by their IR spectra, and the spectra analyzed in the light of the results of theoretical calculations.     

Thermal decomposition of the perfluorinated peroxides CF3OC(O)OOC(O)F and CF3OC(O)OOCF3

Gas phase thermal decomposition of CF(3)OC(O)OOC(O)F and CF(3)OC(O)OOCF(3) was studied at temperatures between 64 and 98 degrees C (CF(3)OC(O)OOC(O)F) and 130-165 degrees C (CF(3)OC(O)OOCF(3)) using FTIR spectroscopy to follow the course of the reaction. For both substances, the decompositions were studied with N(2) and CO as bath gases. The rate constants for the decomposition of CF(3)OC(O)OOC(O)F in nitrogen and carbon monoxide fit the Arrhenius equations k(N)2 = (3.1 +/- 0.1) x 10(15) exp[-(29.0 +/- 0.5 kcal mol(-1)/RT)] and k(CO) = (5.8 +/- 1.3) x 10(15) exp[-(29.4 +/- 0.5 kcal mol(-1)/RT)], and that for CF(3)OC(O)OOCF(3) fits the equation k = (9.0 +/- 0.9) x 10(13) exp[-(34.0 +/- 0.7 kcal mol(-1)/RT)] (all in units of inverted seconds). Rupture of the O-O bond was shown to be the rate-determining step for both peroxides, and bond energies of 29 +/- 1 and 34.0 +/- 0.7 kcal mol(-1) were obtained for CF(3)OC(O)OOC(O)F and CF(3)OC(O)OOCF(3). The heat of formation of the CF(3)OCO(2)(*) radical, which is a common product formed in both decompositions, was calculated by ab initio methods as -229 +/- 4 kcal mol(-1). With this value, the heat of formation of the title species and of CF(3)OC(O)OOC(O)OCF(3) could in turn be obtained as Delta(f) degrees (CF(3)OC(O)OOC(O)F) = -286 +/- 6 kcal mol(-1), Delta(f) degrees (CF(3)OC(O)OOCF(3)) = -341 +/- 6 kcal mol(-1), and Delta(f) degrees (CF(3)OC(O)OOC(O)OCF(3)) = -430 +/- 6 kcal mol(-1).     

Infrared and Raman Spectroscopy of Methylcyanodiacetylene (CH3C5N)

A spectroscopic study combining IR absorption and Raman scattering is presented for methylcyanodiacetylene (CH₃C₅N). Gas‐phase, cryogenic matrix‐isolated, and pure solid‐phase substance was analyzed. Out of 16 normal vibrational modes, 14 were directly observed. The analysis of the spectra was assisted by quantum chemical calculations of vibrational frequencies, IR absorption intensities, and Raman scattering activities at density functional theory and ab initio levels. Previous assignments of gas‐phase IR absorption bands were revisited and extended.     

The trifluoromethoxy carbonyl peroxy radical CF3OC(O)OO

CF3OC(O)OO radicals are generated by low-pressure flash thermolysis of CF3OC(O)OOOC(O)OCF3 highly diluted in inert gases and followed by subsequent isolation in an inert-gas matrix at low temperatures. The by-products CO2, COF2, CF3O, and CF3OO are detected. The new peroxy radical is characterized by IR and UV spectroscopy and by its UV photolytic decay which leads to the formation of CF3OO and CO2. According to DFT calculations the exitence of three stable rotamers is predicted and two of them are found experimentally.     

The missing link: triplet fluorocarbonyl nitrene FC(O)N

The elusive triplet fluorocarbonyl nitrene, FC(O)N (X³A′′), has been generated in high yield from matrix‐isolated FC(O)N₃ by ArF excimer laser photolysis (λ=193 nm). As a side product FNCO was formed. The novel nitrene was characterized by IR, UV/Vis, EPR spectroscopy, and quantum‐chemical calculations. All six fundamental vibrations of FC(O)N at 1681.3, 1193.8, 879.8, 646.5, 588.7, and 434.8 cm^?1 (argon matrix, 16 K), their ^12/13C, ^16/18O, and ^14/15N isotopic shifts, and four electronic transitions at T₀=13 890, 25 428, 29 166, and 30 900 cm^?1 that exhibit vibrational fine structures have been detected. Under visible‐light irradiation at λ≥495 nm, FC(O)N reacted with molecular N₂ in the matrix cage at 6 K to give back FC(O)N₃, whereas near‐UV irradiation at λ≥335 nm yielded FNCO. The singlet–triplet energy gaps of different carbonyl nitrenes are discussed.     

Trifluoromethyl trifluoromethanesulfonate (CF3SO2OCF3)

Trifluoromethyl trifluoromethanesulfonate ($\text{1}$) was synthesized by the reaction of silver trifluoromethanesulfonate with trifluoromethyl iodide in a benzene solution. Reaction of $\text{1}$ with an enamine gave trifluoromethanesulfonyl compound. This is the first example of SO₂-O bond fission of alkyl trifluoromethanesulfonate.     

Rate constants for the reactions of OH radicals with CH3OCF2CF3, CH3OCF2CF2CF3, and CH3OCF(CF3)2

The rate constants for the reactions of OH radicals with CH₃OCF₂CF₃, CH₃OCF₂CF₂CF₃, and CH₃OCF(CF₃)₂ have been measured over the temperature range 250–430 K. Kinetic measurements have been carried out using the flash photolysis, laser photolysis, and discharge flow methods combined respectively with the laser induced fluorescence technique. The influence of impurities in the samples was investigated by using gas‐chromatography. The following Arrhenius expressions were determined: k(CH₃OCF₂CF₃) = (1.90) × 10⁻¹² exp[−(1510 ± 120)/T], k(CH₃OCF₂CF₂CF₃) = (2.06) × 10⁻¹² exp[−(1540 ± 80)/T], and k(CH₃OCF(CF₃)₂) = (1.94) × 10⁻¹² exp[−(1450 ± 70)/T] cm³ molecule⁻¹ s⁻¹. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 846–853, 1999     

Methanesulfenyl fluoride, CH3SF, a missing link in the family of sulfenyl halides: formation and characterization through the matrix photochemistry of methyl thiofluoroformate, FC(O)SCH3

Matrix-isolation experiments have afforded the means of preparing the hitherto unknown sulfur(II) fluoride, methanesulfenyl fluoride, CH3SF. Broadband UV-visible irradiation of methyl thiofluoroformate, FC(O)SCH3, isolated in a solid Ar matrix results, first, in photoisomerization of the syn into the anti form of the molecule, and, subsequently, in the elimination of CO with the concomitant formation of CH3SF. Continued irradiation brings about tautomerization of this product with the detachment and migration of a hydrogen from the methyl group to give the molecular complex H2C==S...HF. The changes have been monitored and the photoproducts detected and identified by the IR spectra of the matrices, and the conclusions confirmed: 1) with reference to the corresponding behavior of the perdeuterated molecule FC(O)SCD3; 2) by analogy with the properties of related molecules, for example, ClC(O)SCH3, CH3SCl, and H2C==S...HCl, and; 3) by comparison with the vibrational properties simulated for the different molecules by ab initio and density functional theory methods.     

Kinetics and products of chlorine atom initiated oxidation of HCF2OCF2OCF2CF2OCF2H and HCF2O(CF2O)n‐(CF2CF2O)mCF2H

Smog chamber/FTIR techniques were used to measure k(Cl + HCF₂OCF₂OCF₂‐CF₂OCF₂H) = k(Cl + HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H) = (5.0 ± 1.4) × 10^?17 cm³ molecule^?1 s^?1 in 700 Torr of N₂/O₂ diluent at 296 ± 1 K. The Cl‐initiated atmospheric oxidation of HCF₂OCF₂OCF₂CF₂OCF₂H and the sample of HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H used in this work gave COF₂ in molar yields of (476 ± 36)% and (859 ± 63)%, respectively, with no other observable carbon containing products (i.e., essentially complete conversion of both hydrofluoropolyethers into COF₂). The results are discussed with respect to the atmospheric chemistry and environmental impact of hydrofluoropolyethers of the general formula HCF₂O(CF₂O)_n(CF₂CF₂O)_mCF₂H. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 819–825, 2008     

Ultraviolet Photolysis Studies on XeO4 in Noble‐Gas and F2 Matrices and the Formation and Characterization of a New XeVIII Oxide, (η2‐O2)XeO3

The photolytic behavior of the thermochemically unstable xenon(VIII) oxide XeO₄ was investigated by UV irradiation in noble‐gas and F₂ matrices. Photolysis of Xe¹⁶O₄ or Xe¹⁸O₄ in noble‐gas matrices at 365 nm yielded XeO₃ and a new xenon(VIII) oxide, namely, (η²‐O₂)XeO₃, which, along with XeO₄, was characterized by matrix‐isolation IR spectroscopy and quantum‐chemical calculations. Calculations of the UV spectrum showed that the photodecomposition is induced by an n→σ* transition, but the nature of the excitation differs when different light sources are used. There is strong evidence for the formation of mobile ¹D excited O atoms in the case of excitation at 365 nm, which led to the formation of (η²‐O₂)XeO₃ by reaction with XeO₄. Matrix‐isolation IR spectroscopy in Ne and Ar matrices afforded the natural‐abundance xenon isotopic pattern for the ν₃(T₂) stretching mode of Xe¹⁶O₄, and ¹⁸O enrichment provided the ¹⁶O/¹⁸O isotopic shifts of XeO₄ and (η²‐O₂)XeO₃.     

ESR study of radicals formed by the reduction of α-diketones C(O)C(O)CF3 (R=(CF3)2CF, C6F5, (CF3)3C) with several group I–III metals

The ESR spectra of radical anions formed by reduction of α-diketones RC(O)C(O)CF₃ (R=(CF₃)₂CF, C₆F₅, (CF₃)₃C) with metals (Li, Na, K, Mg, Cd, Zn, Hg, In, and TI) in THF were studied. For R=(CF₃)₂CF and C₆F₅, the radical anions are formed ascis-isomers, whereas for R=(CF₃)₃C,trans-isomers are obtained. Line broadening due to solvation and desolvation of the cation is observed in the latter case. The reduction of α-diketone (CF₃)₂CFC(O)C(O)CF₃ with Group II metals (Mg, Cd, Zn) results in the formation of radical pairs. Translated fromIzvestiya Akadmii Nauk. Seriya Khimicheskaya, No. 11, pp. 2228–2231, November, 1998.