Kinetics of tetrachloroethylene photochlorination

Photochlorination of tetrachloroethylene has been studied in a homogeneous liquid system. Kinetic parameters such as reaction orders for chlorine, tetracholoroethylene and light intensity, preexponential factor, and activation energy were evaluated from experimental data. The following kinetic equation was obtained by parameter estimation following the Marquardt procedure:      

Kinetics of benzene photochlorination

An empirical approach to the kinetic investigations of photo-initiated liquid-phase chlorination of benzene is presented. Reaction order and the reaction constants for chlorine consumption and for the production of hexachlorocyclohexane isomers were evaluated from experimental data.     

The kinetic isotope effect in the photochlorination of methane

The kinetic isotope effect for the photochemically initiated chlorination of methane-d₂ has been determined. The value is k_H/k_D = 12·1 at 0°C., and the variation with temperature is given by k_H/k_D = 1·09 exp (1300/RT. The results are considered in terms of a semiempirical potential energy surface, and the general subject of the magnitudes of primary kinetic isotope effects is discussed.     

Poly(trifluoroethylene) adsorption and heterogeneous photochlorination reactions

Heterogeneous (gas-solid) photochlorination reactions of poly(trifluoroethylene) (PF 3E) films were studied as a function of reaction time and light intensity. The rate of chlorination was found to be faster in high-intensity light when compared to the reaction in ambient light. PF 3E irreversibly adsorbed to oxidized silicon and covalently attached amine monolayers supported on silicon, producing hydrophobic thin films in the thickness range of 8-40 A. Adsorption conditions such as polymer concentration and solvent composition were investigated. Radical grafting of maleic anhydride to the polymer backbone resulted in increased adsorption on oxidized silicon.     

Synthesis of a solvent-sensitive highly fluorescent derivative of perfluorocyclopentene

A solvent-sensitive highly fluorescent compound, N-[2-(1′,3′,4′,4′,5′,5′-hexafluorocyclopentenyl)]-4-(5-methoxy-thiazolyl)pyridine (1D) was synthesized as an unexpected product of the reaction of 4-bromo-5-methoxy-2-(4-pyridyl)thiazole (1B) with perfluorocyclopentene in the presence of n-BuLi. Primary mechanism of this reaction was proposed, and the photophysical properties of 1D in different solvents were studied.     

Interpretation of the infrared and laser-Raman spectra of cyclopentene and perfluorocyclopentene

The infrared spectra of gaseous and polycrystalline cyclopentene and perfluorocyclopentene have been recorded from 3500 to 200 cm^?1. Raman spectra of the gaseous, liquid and crystalline states for the respective molecules have also been studied and depolarization values determined. In addition, the farinfrared spectrum of solid perfluorocyclopentene has been recorded from 33 to 300 cm^?1. The 33 normal modes of each molecule have been assigned on the basis of the measured depolarization ratios, relative band intensities and group frequency correlations. A series of lines associated with the Δv = 2 transitions of the ring-puckering vibration of gaseous cyclopentene were readily detected in the Raman spectrum. The ring-puckering fundamental of perfluorocyclopentene is assigned to the Raman line centered at 100 cm^?1. The data for these molecules will be discussed in conjunction with similar studies on other cyclic systems.     

Facile synthesis of hypercrosslinked resin via photochlorination of p-xylene and succedent alkylation polymerization

A combination of photochlorination of p-xylene and succedent Friedel-Crafts alkylation polymerization was firstly used in the preparation of the hypercrosslinked adsorptive resin.The data of GC-MS and GC showed that a series of chlorizates were produced when p-xylene was photochlorinated.Hypercrosslinked resins could be synthesized by copolymerization,self-polymerization of chlorizates or post crosslinking reaction.The chemical structure and micromorphology of the porous resins were characterized by BET,FT-IR,SEM and elementary analysis(EA).The results showed that the novel adsorptive resins possess high BET surface near to 1038 m~2/g and large pore volumes range from 0.5 to 1.2 cm~3/g.     

Rotating sector study of the gas phase photochlorination of 2,2-dichloro-1,1,1-trifluoroethane

The rate constant for the combination of 2,2-dichloro-1,1,1-trifluoroethyl radicals has been measured by applying the rotating sector technique to the gas phase photochlorination of 2,2-dichloro-1,1,1-trifluoroethane at 315°K. The observed value is 6.89 × 10¹² cc/mole.sec. This value is in excellent agreement with measurements by Wampler and Kuntz which yielded a temperature-independent value of 6.6 × 10¹² cc/mole.sec. The measurement by Wampler and Kuntz was determined from the photochemical system (CF₃CCl₃ + C-C₆H₁₂ + hν). The Arrhenius parameters for the reaction CF₃CCl₂· + Cl₂ → CF₃CCl₃ + Cl were found to be given by the expression log k₃ = 12.10 ? 5830/2.3RT (units in mole, cc, and sec). This is a relatively high activation energy for a chlorination reaction and makes the reaction ever slower than the chlorination of chloroform.     

Tunneling dynamics and spatial correlations of long chain growth in solid-state photochlorination of ethylene at low temperatures

A novel method is described for preparing reactive cryocrystals by deposition of argondiluted reactant beams and subsequent crystallization during evaporation of the inert gas. Photochlorination of equimolecular ethylene—chlorine mixtures obtained by this method and studied by means of kinetic UV- and IR-spectroscopy reveals activationless chain growth with mean length 300 units in the temperature range 17–45 K. Mean chain lengths greater than 100 are observed up to the conversion degree of 0.6–0.7. Comparison of the experimental data with computer simulations shows that the tunneling reaction is due to the formation of a closely packed reaction complex with high amplitudes of zero-point vibrations which lower the reaction barrier. The commensurability of reactant and product crystal lattices results in linear propagation of chains without accumulation of deformation strain. The chain termination mechanism associated with the spatial correlations of chains is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 687–700, April, 1993.The authors are grateful to Academician V.I. Goldanskii, Dr. D.E.Makarov, and Prof. S. Sato for useful discussion and to A.U.Goldschleger for assistance with the experiments.     

Investigation on photochromism of 1,2-bis(1,4-dimethyl-2-phenyl)perfluorocyclopentene

The photochromic diarylethene, 1,2-bis(1,4-dimethyl-2-phenyl)perfluorocyclopentene has been synthesized and its single crystal can be obtained in hexane at -4℃. The structure of diphenylperluorocyclopentene bearing C2/c space group and monoclinic crystal system is very different from that of dithienylperfluorocyclopentene derivatives bearing Pī space group and triclinic crystal system by X-ray crystallographic analysis. The compound undergoes the phototchromic reaction in solution but no optical activity in single crystal. In addition, its optimum conformation in solvent is also discussed.     

Photochromism of bis(2-alkyl-1-benzofuran-3-yl)perfluorocyclopentene derivatives

[reaction: see text] Photochromic diarylethene derivatives having benzofuran heteroaryl groups, bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene and bis(2-butyl-1-benzofuran-3-yl)perfluorocyclopentene, were synthesized, and their photochromic performance was examined in hexane solution as well as in the single-crystalline phase. The compounds exhibited photochromic reactivity even in the single-crystalline phase.     

Thermal decomposition product of 1,2-bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene

1,2-Bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene shows photochromism in n-hexane at room temperature. We have identified a new compound produced by the thermal decomposition in a mixture of cis- and trans-decahydronaphthalene above 100?°C in the absence of light.     

Reaction of perfluorocyclopentene with various carbon nucleophiles--heteroaromatic lithium reagents, enolate and phosphonium ylide

The addition of heteroaromatic lithium reagents 2 to a THF solution of perfluorocyclopentene (1) provided preferentially the corresponding monosubstituted products 5, while the addition of 1 to 2 effectively gave the 1,2-disubstituted products 6 in good to excellent yields. The reaction of 1 with sodiomalonate 3 or phosphonium ylide 4 also proceeded smoothly to form the 1,3-disubstituted product 8 or 10 in high yield, respectively.     

Photochromic 1,2-dihetarylethenes with perfluorocyclopentene bridge: Synthesis and spectral and kinetic study

A spectral and kinetic study was carried out of some substituted 1,2-dithienylperfluorocyclopentenes and 1,2-bis(benzo[b]thienyl)perfluorocyclopentenes suitable for use as photosensitive components of photochromic recording media for optical memory. The introduction of nitro groups into the benzothienyl moieties dramatically decreases photodegradation and increases the fatigue resistance of these photochromes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2697–2700, December, 2005.     

Tunneling dynamics and spatial correlations of long chain growth in solid-state photochlorination of ethylene at low temperatures

A novel method is described for preparing reactive mixed crystals by vapor deposition in argon and subsequent evaporation of the argon. The kinetics of photochlorination chain reactions of ethylene-chlorine mixtures prepared by this method have been studied by dynamic UV and IR spectroscopy. Activationless chain growth occurs with mean length 260±70 in the temperature range 17–45 K. Chain lengths greater than 100 are observed up to 60–70% conversion to products. Comparison of the experimental data with computer simulations shows that the tunneling reaction is due to formation of a close-packed reaction complex with high amplitude zero-point vibrations which lower the vibrationally adiabatic barrier to reaction. The commensurability of reactant and product crystal lattices results in linear propagation of long chains without accumulation of deformation strain. Spatial correlations caused by nonlinear propagation are considered.     

Synthesis, structure, and some reactions of 1,2-bis(2-alkylthio-3-thienyl)perfluorocyclopentene

The synthesis of 1,2-bis(2-ethylthio-3-thienyl)perfluorocyclopentene is described. Metallation with n-BuLi and subsequent treatment with DMF or CO₂ gave the corresponding 5,5-diformyl and dicarboxy derivatives. The structure of 1,2-bis(2-ethylthio-3-thienyl)perfluorocyclopentene was studied by x-ray structural analysis. It was established that the unit cell contains two crystallographically independent molecules with geometrical and conformational parameters close to one another. The thiophene rings were inclined at an angle of 60° to the plane of the perfluorocyclopentene fragment, the thioalkyl groups were disposed antiparallel to it.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 927–933, July, 1998.     

Effect of a perfluorocyclopentene core unit on the structures and photoluminescence of fluorene- and anthracene-based compounds

A novel series of blue luminescent compounds, in which three identical functional groups, such as fluorene, anthracene, and spiro-bifluorene, are linked distortedly around a perfluorocyclopentene core, have been synthesized and characterized. The introduction of a perfluorocyclopentene linkage into the molecular framework leads to an enhancement of the photoluminescence (PL) efficiency and thermal stability. All compounds exhibit intense blue photoluminescence, which has been attributed to fluorene- or anthracene-based π→π* transitions. The maximum emission wavelengths of all compounds at room temperature are in the region of 420-480 nm, with higher PL quantum efficiencies than in 9,10-diphenylanthracene. The electroluminescent (EL) properties of compound 4, 1,2-bis(9,9′-spirobifluoren-2-yl)-3,3,4,4,5,5-hexafluorocyclopentene, were investigated. A multilayer EL device with the configuration of ITO/2TNATA(60 nm)/NPB(20 nm)/ADN:2%-compound-4(35 nm)/Alq₃(20 nm)/LiF(2 nm)/Al has been successfully fabricated.     

Preparation of perfluorocyclopentenylmetal species and their cross-coupling reaction with electrophiles—Remarkable accesses to versatile perfluorocyclopentene derivatives

On treating perfluorocyclopentene with bis(tributylstannyl)cyanocuprate in THF at −78 °C for 1 h, perfluorocyclopentenylstannane was obtained in good yield. The reaction of the fluorinated vinylstannane with n-BuLi in THF at −78 °C for 1 h, followed by addition of carbonyl compounds, gave the corresponding allyl alcohols in good yields. On the other hand, Pd(0)-catalyzed cross-coupling reaction of perfluorocyclopentenylstannane with benzyl chloroformate in THF at reflux temperature for 2 h proceeded smoothly to form the decarbonated coupling product in high yield.     

Synthesis of 1,2-bis[2-methyl-5(3,4-difluorophenyl)-3-thienyl] perfluorocyclopentene

2-Methylthiophene (1) was treated at 0°C with liquid bromine to form 3,5-dibromo-2-methylthiophene (2) which reacted with tributyl borate to give 2-methyl-3-bromo-5-boronate thiophene (3) at −78°C. Treatment of 3 with 3,4-difluorobrombenzene gave 2-methyl-3-bromo-5-(3,4-difluorophenyl)thiophene (4). Finally, a novel photochromic dithienylethene compound, 1,2-bis [2-methyl-5(3,4-difluorophenyl)-3-thienyl]perfluorocyclopentene (DT-1), was synthesized by the reaction of 4 with perfluorocyclopentene at −78°C. The compound (DT-1) was characterized by IR, NMR, MS, elemental analysis and its photochromic behavior was also discussed. __________ Translated from Chinese Journal of Organic Chemistry, 2007, 27(10): 1282–1284 [译自: 有机化学]