The gas-phase photochemistry and thermal decomposition of glyoxylic acid

1985 ◽  
Vol 63 (2) ◽  
pp. 542-548 ◽  
Author(s):  
R. A. Back ◽  
S. Yamamoto
Keyword(s):  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Absorption Spectrum ◽  
Gas Phase ◽  
Singlet State ◽  
Glyoxylic Acid ◽  
Static System ◽  
First Order ◽  
Increasing Temperature ◽  
Homogeneous Formation

The photolysis of glyoxylic acid vapour has been studied at five wavelengths, 382, 366, 346, 275, and 239 nm, and pressures from about 1 to 6 Torr, at a temperature of 355 K. Major products were CO2 and CH2O, initially formed in almost equal amounts, while minor products were CO and H2. Except at 382 nm, the system was complicated by the rapid secondary photolysis of CH2O. Three primary processes are suggested, each involving internal H-atom transfer followed by dissociation.The absorption spectrum is reported and shows the three distinct absorption systems. A finely-structured spectrum from about 320 to 400 nm is attributed to a transition to the first excited π* ← n+ singlet state; a more diffuse absorption ranging from about 290 nm to a maximum at 239 nm is assigned to the π* ← n− state, while a much stronger absorption beginning below 230 nm is attributed to the π* ← π transition. Product ratios vary with wavelength and depend on which excited state is involved.The thermal decomposition was studied briefly in a static system at temperatures from 470 to 710 K and pressures from 0.4 to 8 Torr. Major products were again CO2 and CH2O, but the latter was always less than stoichiometric. First-order rate constants for the apparently homogeneous formation of CO2 are described by Arrhenius parameters log A (s−1) = 7.80 and E = 30.8 kcal/mol. Carbon monoxide and H2 were minor products, and the CO/CO2 ratio increased with increasing temperature and showed some surface enhancement at lower temperatures. The SF6-sensitized thermal decomposition of glyoxylic acid, induced by a pulsed CO2 laser, was briefly studied, with temperatures estimated to be in the 1100–1600 K range, and the CO/CO2 ratio increased with increasing temperature, continuing the trend observed in the static system.

Photolysis of ketene. I

1968 ◽  
Vol 46 (14) ◽  
pp. 2353-2360 ◽  
Author(s):  
A. N. Strachan ◽  
D. E. Thornton
Keyword(s):  
Carbon Monoxide ◽  
Quantum Yield ◽  
Triplet State ◽  
Singlet State ◽  
Inert Gases ◽  
Inert Gas ◽  
Excited Singlet State ◽  
Intersystem Crossing ◽  
Excited Singlet ◽  
Increasing Temperature

Ketene has been photolyzed at 3660 and 3130 Å both alone and in the presence of the inert gases C4F8 and SF6. The quantum yield of carbon monoxide has been determined at both wavelengths as a function of pressure and temperature. At 3660 Å the quantum yield decreases with increasing pressure but increases with increasing temperature. At 3130 Å the quantum yield with ketene alone remains 2.0 at both 37 and 100 °C at pressures up to 250 mm. At higher pressures of ketene or with added inert gas the quantum yield decreases with increasing pressure. The results are interpreted in terms of a mechanism in which intersystem crossing from the excited singlet state to the triplet state occurs at both wavelengths, and collisional deactivation of the excited singlet state by ketene is single stage at 3660 Å but multistage at 3130 Å.

COMPARATIVE ANALYSIS OF THE CONTENT OF TOXIC SUBSTANCES IN THE GAS PHASE OF AEROSOL OF CIGARETTES AND HEATED TOBACCO STICKS FOR ELECTRIC TOBACCO HEATING SYSTEMS

2020 ◽  
Author(s):  
С.Н. МЕДВЕДЕВА ◽  
Т.А. ПЕРЕЖОГИНА ◽  
Е.В. ГНУЧИХ
Keyword(s):  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Comparative Analysis ◽  
Gas Phase ◽  
Control Sample ◽  
Toxic Substances ◽  
Heating Systems

Представлены результаты анализа содержания монооксида углерода, бензола, 1,3-бутадиена в газовой фазе аэрозоля (ГФА) образцов нагреваемых табачных палочек (стики) для электрических систем нагревания табака, пяти марок коммерческих сигарет, контрольной сигареты 3R4F с помощью тестирования на курительной машине в стандартном режиме прокуривания ISO и интенсивном ISO Intense. Установлено значительное снижение содержания монооксида углерода, бензола и 1,3-бутадиена в аэрозоле образцов стиков по режиму ISO Intense и ISO. Количество образующегося монооксида углерода в ГФА образцов стиков составляет 2% от его содержания в ГФА образца контрольных сигарет 3R4F, что подтверждает отсутствие процессов термического разложения (пиролиза) табака. Определено, что в ГФА образцов стиков содержится значительно меньше вредных и потенциально опасных соединений. Установлено снижение содержания бензола и 1,3-бутадиена более чем на 99% по сравнению с контрольным образцом 3R4F и пятью образцами популярных в России марок сигарет. The results of the analysis of the content of carbon monoxide, benzene, 1,3-butadiene in the aerosol gas phase (AGPh) of heated tobacco sticks for electric tobacco heating systems, five brands of commercial cigarettes, 3R4F control cigarette using testing on a Smoking machine in standard ISO smoking mode and ISO Intense are presented. A significant decrease in the content of carbon monoxide, benzene and 1,3-butadiene in stick aerosols according to the ISO Intense and ISO modes was found. The amount of carbon monoxide produced in the effluent AGPh is 2% of its content in the AGPh of 3R4F control cigarettes, which confirms the absence of thermal decomposition (pyrolysis) of tobacco. It was determined that the AGPh of verses contains significantly fewer harmful and potentially dangerous compounds. A decrease in the content of benzene and 1,3-butadiene was found by more than 99% compared to the control sample of 3R4F cigarettes and five brands of cigarettes popular in Russia.

The Near-ultraviolet Absorption Spectrum of Diimide in Liquid Ammonia and its Decomposition between −65 and −38 °C

1974 ◽  
Vol 52 (13) ◽  
pp. 2513-2515 ◽  
Author(s):  
R. A. Back ◽  
C. Willis
Keyword(s):  
Absorption Spectrum ◽  
Gas Phase ◽  
Room Temperature ◽  
Liquid Ammonia ◽  
Vibrational Structure ◽  
Ultraviolet Absorption ◽  
Ultraviolet Absorption Spectrum ◽  
First Order ◽  
Rapid Decomposition ◽  
Near Ultraviolet

The near-ultraviolet absorption spectrum of diimide in liquid ammonia at −50 °C is shifted about 500 Å to the red compared with the gas-phase spectrum, with λmax = 4000 Å. The spectrum is also broadened and the vibrational structure largely obscured. It is suggested that hydrogen bonding is responsible for these changes.Diimide is much more stable in liquid ammonia between −65 and −38 °C than in the gas phase at room temperature. A first-order decay is observed with Arrhenius parameters of A = 1.9 × 103 s−1 and E = 6.6 kcal/mol; this is always preceded by a more rapid, higher-order initial decay which may be related to the rapid decomposition observed during vaporization.

Catalysis by hydrogen halides in the gas phase. XVIII. Methyl formate and hydrogen bromide

1968 ◽  
Vol 21 (7) ◽  
pp. 1711
Author(s):  
DA Kairaitis ◽  
VR Stimson
Keyword(s):  
Carbon Monoxide ◽  
Gas Phase ◽  
Decomposition Product ◽  
Methyl Formate ◽  
Arrhenius Equation ◽  
Hydrogen Bromide ◽  
Radical Chain ◽  
Hydrogen Halides ◽  
Chain Decomposition ◽  
First Order

Hydrogen bromide catalyses the decomposition of methyl formate into carbon monoxide and methanol at 390-460�. The radical chain decomposition product, methane, is formed in only a small amount that is further reduced by the addition of inhibitor. The reaction is homogeneous and molecular, is first order in each reactant, and follows the Arrhenius equation: k2 = 1012.50exp(-32200/RT)sec-1 ml mole-1 It is not reversed by added methanol.

THE KINETICS OF CUPRENE GROWTH

1950 ◽  
Vol 28b (7) ◽  
pp. 358-372
Author(s):  
Cyrias Ouellet ◽  
Adrien E. Léger
Keyword(s):  
Nitric Oxide ◽  
Activation Energy ◽  
Carbon Monoxide ◽  
Apparent Activation Energy ◽  
Copper Catalyst ◽  
Maximum Velocity ◽  
Static System ◽  
Reaction Velocity ◽  
First Order ◽  
Kinetics Of

The kinetics of the polymerization of acetylene to cuprene on a copper catalyst between 200° and 300 °C. have been studied manometrically in a static system. The maximum velocity of the autocatalytic reaction shows a first-order dependence upon acetylene pressure. The reaction is retarded in the presence of small amounts of oxygen but accelerated by preoxidation of the catalyst. The apparent activation energy, of about 10 kcal. per mole for cuprene growth between 210° and 280 °C., changes to about 40 kcal. per mole above 280 °C. at which temperature a second reaction seems to set in. Hydrogen, carbon monoxide, or nitric oxide has no effect on the reaction velocity. Series of five successive seedings have been obtained with cuprene originally grown on cuprite, and show an effect of aging of the cuprene.

Theoretical Study of the Kinetics and Mechanism of the Thermal Decomposition of 3-Oxetanone in the Gas Phase

2017 ◽  
Vol 42 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Mohammad Khavani ◽  
Javad Karimi
Keyword(s):  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Ethylene Oxide ◽  
Gas Phase ◽  
Transition States ◽  
Decomposition Reaction ◽  
Kinetics And Mechanism ◽  
Methyl Radical ◽  
Decomposition Products ◽  
Concerted Mechanism

The kinetics and mechanism of the thermal decomposition reaction of 3-oxetanone in the gas phase were studied using quantum chemical calculations. The major products of this reaction are formaldehyde, ketene, carbon monoxide, ethylene oxide, ethylene and methyl radical. Formaldehyde, ketene, carbon monoxide and ethylene oxide are the initial decomposition products and other species are the products of ethylene oxide decomposition. The results of B3LYP and QCISD(T) calculations reveal that thermal decomposition of 3-oxetanone to ethylene oxide and carbon monoxide is more probable than to formaldehyde and ketene from an energy viewpoint. Moreover, quantum theory of atoms in molecules and natural bond orbital analysis indicate that 3-oxetanone decomposition to formaldehyde, ketene, carbon monoxide and ethylene occurs via a concerted mechanism and bonds that are involved in the transition states have a covalent character. Moreover, the calculated changes in bond lengths in the transition states reveal that bond breaking and new bond formation occur asynchronously in a concerted mechanism.

The visible absorption spectrum of 1,2-cyclobutanedione in the gas phase

1986 ◽  
Vol 64 (11) ◽  
pp. 2152-2161 ◽  
Author(s):  
R. A. Back ◽  
J. M. Parsons
Keyword(s):  
Absorption Spectrum ◽  
Gas Phase ◽  
Singlet State ◽  
Energy Levels ◽  
Vibrational Structure ◽  
Visible Absorption Spectrum ◽  
Excited Singlet ◽  
Bending Vibration ◽  
Visible Absorption ◽  
Out Of Plane

The visible absorption spectrum of 1,2-cyclobutanedione has been measured in the gas phase at wavelengths between 4000 and 5100 Å. The absorption is attributed to the allowed π* ← n+, 1B1 ← 1A1 transition corresponding to the first excited singlet state. The spectrum shows a complex well-resolved vibrational structure which has been analysed, with some 125 bands measured and assigned. The bands at the longer wavelengths show sharp rotational fine structure, not yet analysed. The strongest band in the spectrum at 4933 Å has been assigned as the 0–0 band, while a band almost as strong at 4820 Å is attributed to excitation of one quantum of [Formula: see text], the a2 out-of-plane carbonyl bending vibration, and it is suggested that this band owes its intensity to vibronic coupling. A number of symmetric vibrations are also excited in the spectrum, but with no long progressions. Sequence bands running to the blue with an interval of about 72 cm−1 are prominent throughout the spectrum, and are assigned to v13, the a2 ring-twisting vibration. Other hot bands were also observed involving v13 which permitted estimation of energy levels for this vibration both in the ground state and the excited state. The infrared spectrum was also measured and analysed in the gas phase between 600 and 4000 cm−1, and 14 bands were assigned to fundamental vibrations; some of these assignments, at the lower frequencies, are uncertain.

The thermal decomposition of cyclobutane-1,2-dione

1985 ◽  
Vol 63 (11) ◽  
pp. 2945-2948 ◽  
Author(s):  
J.-R. Cao ◽  
R. A. Back
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Vapor Pressure ◽  
Gas Phase ◽  
Rate Constant ◽  
Surface Reaction ◽  
Order Rate Constant ◽  
Reaction Vessel ◽  
Arrhenius Parameters ◽  
First Order

The thermal decomposition of cyclobutane-1,2-dione has been studied in the gas phase at temperatures from 120 to 250 °C and pressures from 0.2 to 1.5 Torr. Products were C2H4 + 2CO, apparently formed in a simple unimolecular process. The first-order rate constant was strongly pressure dependent, and values of k∞ were obtained by extrapolation of plots of 1/k vs. 1/p to1/p = 0. Experiments in a packed reaction vessel showed that the reaction was enhanced by surface at the lower temperatures. Arrhenius parameters for k∞, corrected for surface reaction, were log A (s−1) = 15.07(±0.3) and E = 39.3(±2) kcal/mol. This activation energy seems too low for a biradical mechanism, and it is suggested that the decomposition is probably a concerted process. The vapor pressure of solid cyclobutane-1,2-dione was measured at temperatures from 22 to 62 °C and a heat of sublimation of 13.1 kcal/mol was estimated.

The gas-phase thermal decomposition of cyclobutanol

1982 ◽  
Vol 60 (20) ◽  
pp. 2537-2541 ◽  
Author(s):  
R. A. Back
Keyword(s):  
Thermal Decomposition ◽  
Gas Phase ◽  
Hydrogen Transfer ◽  
Frequency Factor ◽  
Static System ◽  
Cyclic Transition ◽  
Surface Catalysis ◽  
Cyclic Transition State ◽  
Strong Surface ◽  
A Minor

The thermal decomposition of cyclobutanol has been studied in the gas phase in a static system at pressures from 3–6 Torr and temperatures from 250 to 450 °C. The major products observed were ethylene and acetaldehyde, while n-butyraldehyde was a minor product. First-order rate constants based on ethylene formation in a Pyrex vessel conditioned by carbon deposition gave Arrhenius parameters of A = 2.14 (± 0.2) × 1014 s−l and E = 57.3 (± 1) kcal/mol. Under the same conditions, the ratio n-butyraldehyde/ethylene increased with decreasing temperature, corresponding to an activation energy of about 50 kcal/mol for butyraldehyde formation and a frequency factor about 104 times lower than that for ethylene production. In an untreated Pyrex vessel the decomposition showed strong surface catalysis with much lower activation energies for both processes. It is suggested that both ethylene and n-butyraldehyde are formed from a common ĊH2CH2CH2ĊHOH biradical by cleavage and by hydrogen transfer through a 6-membered cyclic transition state respectively. The thermal decomposition is thus the reverse of the Type II and II′ processes observed in the photolysis of n-butyraldehyde.

Di-tert-butyl peroxide decomposition behind shock waves

1976 ◽  
Vol 54 (4) ◽  
pp. 581-585 ◽  
Author(s):  
David K. Lewis
Keyword(s):  
Thermal Decomposition ◽  
Gas Phase ◽  
Single Pulse ◽  
First Order ◽  
Tert Butyl ◽  
First Order Kinetics ◽  
Peroxide Decomposition ◽  
Butyl Peroxide ◽  
Temperature Work ◽  
Lower Temperature

The homogeneous, gas phase thermal decomposition of di-tert-butyl peroxide has been studied in a single pulse shock tube. Samples containing 0.05% to 0.5% reactant in argon were heated to 528–677 K at total pressures of about 1 atm. Acetone and ethane were the only significant products. The reaction obeyed first order kinetics. The Arrhenius parameters, log A (s−1) = 15.33 ± 0.50, Eact (kJ/mol) = 152.3 ± 5.8, are in agreement with the bulk of the earlier reported results of lower temperature work, and with a recently reported result obtained via the very low pressure pyrolysis technique. Indications from some of the earlier work that the A factor may decline at high temperatures are not supported by the present study.

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