F:Flammable;
71-43-2Relevant articles and documents
Photochemistry of Benzene Isomers. 1. Fulvene and 3,4-Dimethylenecyclobutene
Kent, Jay E.,Harman, Peter J.,O'Dwyer, Michael F.
, p. 2726 - 2730 (1981)
The photochemical behavior of the benzene isomer fulvene is investigated at various excitation wavelengths.The only observable photoproduct is benzene, produced in high quantum yield below about 275-nm excitation.The quantum yield is dependent upon excitation wavelength indicating the photoisomerization requires vibrational activation.Quenching by various added gases is efficient and suggests that the photochemistry does not invove triplet-state or free-radical mechanisms.Another isomer, 3,4-dimethylenecyclobutene, also shows photochemical behavior upon excitation at 240 and 215 nm to produce a polymeric material.
Alkylation of benzene by alkyl cations. Stability of the tert-butyl benzenium ion
Sharma, D. K. Sen,Ikuta, S.,Kebarle, P.
, p. 2325 - 2331 (1982)
The kinetics and eqilibria of the gas phase reaction tert-C4H9+ + C6H6 = tert-C4H9C6H6+ were studied with a high ion source pressure pulsed electron beam mass spectrometer.Equilibria could be observed in the temperature range 285-325 K, van't Hoff plots of the equilibrium constants led to ΔH10 = -22+/-2 kcal mol-1 and ΔS10 = -49+/-5 cal K-1 mol-1.The rate constants at 305 K were k1f = 1.5*10-28 molecules-2 cm6 s-1 and k1r = 2.9*10-19 molecules-1 cm3 s-1. tert-C4H9C6H6+ dissociates easily via not only because of the low dissociation energy (-ΔH10) but also because of the unusually favorable entropy (-ΔS10).The occurence of transalkylation reactions: tert-C4H9C6H6+ + alkylbenzene = tert-C4H9 alkylbenzene+ + benzene, was discovered in the present work.
Pyrolysis of Styrene. Kinetics and Mechanism of the Equilibrium Styrene Benzene + Acetylene
Grela, M. A.,Amorebieta, V. T.,Colussi, A. J.
, p. 9861 - 9865 (1992)
The thermal unimolecular decomposition of styrene into benzene and acetylene, C6H5CH=CH2 -> C6H6 + HCCH (1), was investigated in a low pressure (ca. 10 mTorr) flow reactor by on-line mass spectrometry between 1180 and 1350 K.Measured rates can be calculated, via RRKM extrapolation, from the expression log (K1, s-1) = 14.38 - 17076/T, which was derived by detailed balance from high-pressure (ca. 50 Torr) low-temperature (878-973 K) kinetic data for the reverse reaction.This value of E1 = 77.9 kcal/mol allows for the generation of vinylidene, H2C=C:; the carbene isomer of acetylene, as a primary product of the title reaction.A non-radical process involving the rate-determining extrusion of H2C=C: from a -7-methylene cyclohepta-2,4-diene intermediate in equilibrium with styrene is consistent with kinetic and thermochemical considerations.
Kinetic Parameters for the Unimolecular Dissociation of Styrene Ion
Dunbar, Robert C.
, p. 3283 - 3286 (1990)
Time-resolved photodissociation measurements of the laser-induced fragmentation of styrene molecular ion have been carried out at 355 nm.Taking thermal energy content into account, a unimolecular dissociation rate of 6.3 * 103 s-1 at an internal energy of 3.66 eV was derived.The new measurement has been combined with previous data from photodissociation and photoionization to give a dissociation rate-energy curve spanning 2 decades of rate values.By RRKM fitting to this curve, unimolecular kinetic parameters E0 = 2.43 +/- 0.05 eV and ΔS% (1000K) = -3.9 +/- 1 cal mol-1 K-1 were derived.The conclusion that this dissociation proceeds through a rate-limiting thight activated complex at E0 = 2.43 eV was affirmed.
Probing ensemble effects in surface reactions. 3. Cyclohexane adsorption on clean and bismuth-covered Pt(III)
Rodriguez,Campbell
, p. 826 - 835 (1989)
The adsorption and chemistry of cyclohexane on clean and Bi-covered Pt(111) surfaces have been studied with thermal desorption mass spectroscopy (TDS), deuterium labeling, Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS). The thermal experiments show that, on clean Pt(111), cyclohexane is adsorbed in three molecular states with desorption temperatures of approx. 236 (monolayer), approx. 181 (second monolayer), and approx.154 K (multilayer). There is little isotopic exchange in the molecularly desorbing cyclohexane. Benzene is formed at approx. 236 K on the clean Pt(111) surface is a product of the dehydrogenation of adsorbed cyclohexane. This process is 13-fold slower for perdeuterated cyclohexane. An analysis of quantitative XPS data and the effect of Bi poisoning on the chemisorption of cyclohexane shows that an ensemble of about five Pt atoms is necessary to chemisorb C6H12. The dehydrogenation of adsorbed cyclohexane is poisoned at very low bismuth coverages (θ$-Βi$/0.1) according to mechanism dominated by steric, site-blocking effects.
Infrared multiphoton dissociation of styrene ions by low-power continuous CO2 laser irradiation
Dunbar, Robert C.,Zaniewski, Rebecca C.
, p. 5069 - 5075 (1992)
The kinetics of infrared multiphoton dissociation of styrene ions under collision-free conditions in the ion cyclotron resonance ion trap were studied as a function of the intensity of the cw CO2 laser at powers up to 6 W.Following the beginning of irradiation an induction time was observed.Followed by dissociation according to a first-order rate constant.The kinetics could be fitted to a random-walk simulation of a master-equation model, in the same way as previous studies.A matrix-algebra solution of the master-equation model is described which gave a better fit with greater computational convenience.From the modeling the rate of radiation of infrared photons (assumed to be at 940 cm-1) from the ions was estimated as 350 s-1 at an ion internal energy of around 3 eV.When the dissociation threshold E, was treated as an unknown it was found that master-equation modeling of the kinetic results could give an estimate of Et, but with large uncertainty.Application of simple thermal kinetic theory via Tolman's theorem gave good qualitative understanding of the results, and predicted the intensity dependence of the dissociation rate with a deviation of about 30percent.
Kinetic Energy Release in Thermal Ion-Molecule Reactions: Single Charge-Transfer Reactions of V2+ and Ta2+ with Benzene
Gord, James R.,Freiser, Ben S.,Buckner, Steven W.
, p. 8274 - 8279 (1991)
Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) has been used to study the single charge-transfer reactions of V2+ and Ta2+ with benzene under thermal conditions.Thermal charge-transfer rate constants of 2.0 x 10-9 and 1.2 x 10-9 cm3 molecule-1s-1 were measured for V2+ and Ta2+, respectively.The total kinetic energy of the product ions was determined to be 1.91 +/- 0.50 eV for the V2+ case and 2.82 +/- 0.50 eV for the Ta2+ case.These results and a previous study of the Nb2+ - benzene single charge-transfer system suggest a simple long-distance electron-transfer mechanism proceeding by ionization of the 1a2u orbital of benzene with significant internal excitation of the nascent C6H6+ product.
Methane chemistry in the hot supersonic nozzle
Somorjai,Kim,Romm
, p. 7025 - 7030 (2001)
The combination of pyrolysis and expansion to a supersonic molecular beam was shown to be very effective in conversion of pure CH4 to heavier hydrocarbons. Pure CH4 conversion reached 70% when it reacted in a hot (1000°-1150°C) supersonic nozzle made of quartz with 100 μ dia orifice. Hydrogen, acetylene, benzene, methyl, and propargyl radicals were the major products in the distribution. CH4 conversion rate was not improved with the addition of O2, NO, or CO2 as O2 reacted primarily with surface carbon formed by CH4 decomposition. No oxygen containing hydrocarbon derivatives were observed. The lifetime of the nozzle was longer than pure CH4 as a reactant resulting from surface carbon removal by oxygen. The mechanism involved pyrolytic rather than catalytic surface generation of free hydrocarbon radicals with subsequent coupling to heavier hydrocarbon products prior to desorption to the gas phase and expansion to the supersonic beam.
Facile formation of benzene from a novel cyclohexane derivative
Liu, Xiadong,Zhang, Guangtao,Verkade, John G.
, p. 4449 - 4451 (2001)
Upon acidification, benzene forms at room temperature from the novel 1,3,5-cis-trisubstituted cyclohexane wherein the substituents are the azido phosphine cage moieties N3P(MeNCH2CH2)3N. The dominant reaction in the decomposition of this unusually thermally stable intermediate in the presence of HA is the formation of nitrogen and the salt [H2N=P(MeNCH2CH2)3N]A in addition to benzene. Evidence for a transannulated cage intermediate is presented.
Reaction of Hydrogen Atom with Benzene: Kinetics and Mechanism
Nicovich, J. M.,Ravishankara, A. R.
, p. 2534 - 2541 (1984)
The rate coefficients for the reactions H + C6H6 -> products (k1) (1), H + C6D6 -> products (k2) (2), D + C6H6 -> products (k3) (3), and D + C6D6 -> products (k4) (4) have been measured in the temperature range of 298-1000 K by using the pulsed photolysis-resonance fluorescence technique.On the basis of the obtained kinetic information, it is shown that the primary path in all these reactions is addition of the atom to the benzene ring form cyclohexadienyl radical.The rate coefficient for the thermal decomposition of the cyclohexadienyl radical has also been measured.When the rate coefficients for the formation and decomposition of the cyclohexadienyl radical are used, the standard heat of formation of cyclohexadienyl radical at 298 K is calculated to be 45.7 kcal/mol.The measured values of k1-k4 are compared with the results of previous investigations.Most of the observed kinetic behavior in these reactions has been explained on the basis of the addition-decomposition reaction scheme.
