scholarly journals The thermal decomposition of acetaldehyde and the existence of different activated states

1933 ◽  
Vol 141 (843) ◽  
pp. 41-55 ◽  
Keyword(s):  
High Pressures ◽  
Initial Pressure ◽  
Bimolecular Reaction ◽  
Bimolecular Reactions ◽  
First Order ◽  
Straight Line ◽  
Gas Reactions ◽  
Pass Through ◽  
Low Pressures ◽  
Kinetics Of

Homogeneous thermal gas reactions were at one time tacitly assumed to possess a definite order, unimolecular and bimolecular reactions, for example, being sharply distinguished. The kinetics of the decomposition of acetalde­ hyde, CH 3 CHO = CH 4 + CO, over the pressure range of 100 to 400 mm. were found to satisfy the criterion of a bimolecular reaction, namely, that the reciprocal of the time for half change (1/ t 1/2 ) )plotted against the initial pressure ( p 0 ) gave a straight line inclined to the axes. The line, however, did not pass through the origin, as may be seen in fig. 1 of the present paper. This indicated the presence of some first order reaction, the nature of which was not determined. Subsequently, in accordance with the collision theory of activation and deactivation, it was shown that certain reactions, sometimes called quasiummolecular, change their order from the second at low pressures to the first at high pressures. This apparently was the reverse of the behaviour shown by acetaldehyde.

THE KINETICS OF THE DECOMPOSITION REACTIONS OF THE LOWER PARAFFINS: II. ISOBUTANE

1938 ◽  
Vol 16b (8) ◽  
pp. 260-272 ◽  
Author(s):  
E. W. R. Steacie ◽  
I. E. Puddington
Keyword(s):  
Rate Constants ◽  
Pressure Range ◽  
Reaction Rate ◽  
High Pressures ◽  
Initial Pressure ◽  
First Order ◽  
Decomposition Reactions ◽  
Order Rate ◽  
Reaction Proceeds ◽  
Kinetics Of

The kinetics of the thermal decomposition of isobutane has been investigated over an initial pressure range of from 5 to 60 cm., and at temperatures from 522 to 582 °C. The initial first order rate constants at high pressures are given by[Formula: see text]The results are in general agreement with those obtained by previous investigators. The reaction rate falls off with diminishing pressure, and the first order rate constants in a given run diminish strongly as the reaction proceeds. This behavior is similar to that of n-butane.Analyses of the products of the reaction were made at various stages, temperatures, and initial pressures by low-temperature distillation in a still of the Podbielniak type. The initial products were found by extrapolation to be H2, 35; CH4, 14; C2H4, 0.9; C2H6, 0.9; C3H6, 14; and C4H8, 35%. The results are compared with those of other workers.

THE THERMAL DECOMPOSITION OF ETHANE: PART III. SECONDARY REACTIONS

1966 ◽  
Vol 44 (20) ◽  
pp. 2369-2380 ◽  
Author(s):  
M. C. Lin ◽  
M. H. Back
Keyword(s):  
High Temperatures ◽  
Low Temperatures ◽  
High Pressures ◽  
Thermal Dissociation ◽  
First Order ◽  
Butyl Radical ◽  
Secondary Reactions ◽  
Low Pressures ◽  
Kinetics Of ◽  
Subsequent Decomposition

The kinetics of the secondary reactions producing methane, butane, and butene-1 in the pyrolysis of ethane have been investigated over the temperature range 550–726 °C and at pressures from 600–10 mm. The rate of secondary methane production was second order in ethylene at high pressures but was first order in ethylene at low pressures and high temperatures. In the latter region it is concluded that isomerization of the n-butyl radical to sec-butyl with subsequent decomposition to CH3 + C3H6 was the main source of methane. The rate of butane formation increased with time at low temperatures and decreased with time at high temperatures. It is shown that the decrease in rate was mainly due to the thermal dissociation of butane. The main source of butene-1 was probably decomposition of the n-butyl radical.

scholarly journals The thermal decomposition of nitrous oxide at pressures up to forty atmospheres

1934 ◽  
Vol 144 (852) ◽  
pp. 386-412 ◽  
Keyword(s):  
Activation Energy ◽  
Nitrous Oxide ◽  
Atmospheric Pressure ◽  
Initial Pressure ◽  
Bimolecular Reaction ◽  
Absolute Temperature ◽  
Velocity Constant ◽  
A Value ◽  
Straight Line ◽  
Rate Of Reaction

Nitrous oxide decomposes to nitrogen and oxygen at velocities which can be conveniently measured at temperatures between 600° and 850° C. M. A. Hunter investigated the reaction by streaming the gas through a porcelain bulb in a furnace and measuring the decomposition for different times of passage. No attempt was made to determine whether the reaction is homogeneous or heterogeneous. The effect of wide variation of pressure was not used to determine its order, since the reaction was followed only over small ranges of decomposition at atmospheric pressure. From the velocity of decomposition, however, bimolecular constants were obtained which could be represented by the equation: ln k = 24·12 - 31800/T, where k is the bimolecular velocity constant and T the absolute temperature. If this equation holds, the activation energy of the bimolecular reaction is 62,040 cal./gm. mol. A much more thorough examination of the reaction was made by Hinshelwood and Burk, who measured the rate of reaction by following the pressure increase at constant volume in a silica bulb. The reaction was proved to be homogeneous. The initial pressure was varied between 50 and 500 mm. Hg, and it was found that the reciprocal of the half-lives when plotted against the initial pressures gave a straight line. true bimolecular reaction requires the straight line 1/ t ½ = ka , where t ½ is the half-line, and k the velocity constant, and a the initial concentration. The line through the experimental points showed a small intercept on the 1/ t ½ axis for which no explanation was offered at the time. From the variation of the bimolecular constants between 565° and 852° C. the activation energy of the reaction was calculated to be 58,450 cal./gm. mol. If the reaction were a bimolecular one dependent on immediate decomposition at each activating collision of the molecules the number of molecules reacting per second should be equal to Z x e -E/RT , where Z is the number of molecules colliding per second and E is the activation energy. From the observed rate of reaction at 1000° K. a value of 55,000 cal./gm. mol. was found for the activation energy. The fairly close agreement between the two values of the activation energy, 58,450 and 55,000 cal./gm. mol. and the manner in which the half-life varied with pressure provided good grounds for believing the reaction to be a simple bimolecular one, dependent only on collisions between the molecules.

THE KINETICS OF THE DECOMPOSITION REACTIONS OF THE LOWER PARAFFINS: I. n-BUTANE

1938 ◽  
Vol 16b (5) ◽  
pp. 176-193 ◽  
Author(s):  
E. W. R. Steacie ◽  
I. E. Puddington
Keyword(s):  
Reaction Rate ◽  
High Pressures ◽  
The Other ◽  
First Order ◽  
Decomposition Reactions ◽  
Temperature And Pressure ◽  
Products Of Reaction ◽  
Kinetics Of ◽  
Good Agreement ◽  
Mechanism Of The Reaction

The kinetics of the thermal decomposition of n-butane has been investigated at pressures from 5 to 60 cm. and temperatures from 513 to 572 °C. The initial first order rate constants at high pressures are given by[Formula: see text]The results are in good agreement with the work of Frey and Hepp, but differ greatly from that of Paul and Marek. The reaction rate falls off strongly with diminishing pressure; this is rather surprising for a molecule as complex as butane. The first order constants in a given run fall rapidly as the reaction progresses. The last two facts suggest that chain processes may be involved.A large number of analyses of the products of reaction have been made at various pressures, temperatures, and stages of the reaction, the method being that of low-temperature fractional distillation. The products are virtually independent of temperature and pressure over the range investigated. The initial products, obtained by extrapolation to zero decomposition, are:—H2, 2.9; CH4, 33.9; C3H6, 33.9; C2H4, 15.2; C2H6, 14.1%. The mechanism of the reaction is discussed, and the results are compared with those of the other paraffin decompositions.

The kinetics of isomerization of allylbenzene homogeneously catalysed by palladium(II) in acetic acid

1973 ◽  
Vol 26 (12) ◽  
pp. 2635 ◽  
Author(s):  
BI Cruikshank ◽  
NR Davies
Keyword(s):  
Acetic Acid ◽  
Catalytic Activity ◽  
Experimental Evidence ◽  
Active Catalyst ◽  
Bimolecular Reaction ◽  
Equilibrium System ◽  
Constant Concentration ◽  
First Order ◽  
Rate Determining Step ◽  
Kinetics Of

The changes in the kinetics observed during the isomerization of allylbenzene catalysed by palladium(II) are interpreted in terms of the slow formation of a hydrido complex of palladium(II) which subsequently attains a constant concentration in an equilibrium system. The kinetics during these phases are shown to be consistent with first-order dependence on the concentration of an active catalyst formed in a bimolecular reaction from a mononuclear palladium(II) complex and with a regenerative hydrido-π-alkene-σ-alkyl mechanism of isomerization. The hypothesis that a further stage in the kinetics reflects a change in the rate determining step to one involving alkene displacement from the catalyst is supported by the experimental evidence. The concentration of active catalyst is shown not to fall appreciably until all the allylbenzene has undergone isomerization, but thereafter there is a slow reduction of catalytic activity which is not completely restored by the addition of further allylbenzene. It is suggested that the slow formation of a π-allylic complex is responsible.

Mechanistic Information on the Aquations of Complexes of the Pentaamminecobalt(III) Series from Kinetic Studies at High Pressures

1972 ◽  
Vol 50 (17) ◽  
pp. 2739-2746 ◽  
Author(s):  
W. E. Jones ◽  
L. R. Carey ◽  
T. W. Swaddle
Keyword(s):  
High Pressures ◽  
Rate Coefficient ◽  
Kinetic Studies ◽  
Quadratic Equation ◽  
Water Molecules ◽  
First Order ◽  
Unit Slope ◽  
Straight Line ◽  
The Mean ◽  
The Stability

The logarithm of the pseudo-first-order rate coefficient k for the aquation of Co(NH3)5X(3–n)+ can be represented by a quadratic equation in the pressure P, or, better, by[Formula: see text]where P is in kbar, [Formula: see text] is the volume of activation at P = 0, and x is the increase in the number of water molecules solvating the complex as it goes to the transition state. For [Formula: see text]Cl−, Br−,[Formula: see text] and [Formula: see text] at 25° [Formula: see text] and ionic strength I = 0.1 M LiClO4/HClO4, [Formula: see text] −10.6, −9.2, −6.3, and +16.8 cm3 mol−1, and x = 8.0, 4.1, 3.9, 1.9, and −4.2; for Xn− = NCS−, the mean ΔV* from P = 0.001 to 2.5 kbar at 88° is −4 cm3 mol−1. Detailed consideration of these data, especially their correlation with the molar volume of reaction by a straight line of unit slope for [Formula: see text] Cl−, Br−, NO3−, and H2O, provides strong evidence for a dissociative interchange mechanism. For [Formula: see text] the separating entity is probably HN3 rather than [Formula: see text] For Xn− = NCS−, aquation is incomplete, at practical complex concentrations; at 88.0°, 1 bar, and I = 0.1 M LiClO4/HClO4, k = 3.3 × 10−6 s−1 and the stability constant of Co(NH3)5NCS2+ is 490 M−1.

Non-equilibrium kinetics of bimolecular reactions. Part 6. Transient rate coefficients

1994 ◽  
Vol 72 (3) ◽  
pp. 714-720
Author(s):  
Chris Carruthers ◽  
Heshel Teitelbaum
Keyword(s):  
Population Distribution ◽  
Bimolecular Reaction ◽  
Rate Coefficients ◽  
Exchange Reactions ◽  
Equilibrium Conditions ◽  
Bimolecular Reactions ◽  
Wide Range ◽  
Vibrational Population ◽  
Kinetics Of ◽  
Non Equilibrium

The master equation is solved numerically for the time dependence of the vibrational level populations of HCl (treated as a simple harmonic oscillator) during the bimolecular exchange reaction, Br + HCl → HBr + Cl, taking into account the competition between reaction and vibrational equilibration subject to Landau–Teller T–V excitation. Strong deviations from Boltzmann distributions are found. A wide range of reactant concentrations, diluent concentrations and temperatures were explored. It was found that no significant reaction occurs before the establishment of a steady vibrational population distribution, confirming that the rate coefficient for non-equilibrium bimolecular exchange reactions can be determined from a simple analytical steady state treatment (J. Chem. Soc. Faraday Trans. 87, 229 (1991)). The rate of an isolated elementary bimolecular reaction, A + BC → AB + C, under non-equilibrium conditions can deviate seriously from the standard expression, Keq [A][BC], and is better given by the law[Formula: see text]where [R] is the concentration of the collisional equilibrator, R, and a and g are constants depending only on temperature. This generalized rate law describes not only the initial rate but also the rate all the way up to completion, in the absence of the reverse reaction.

scholarly journals Technical note: Entrainment-limited kinetics of bimolecular reactions in clouds

2021 ◽  
Author(s):  
Christopher D. Holmes
Keyword(s):  
Atmospheric Chemistry ◽  
Reaction Rates ◽  
Bimolecular Reaction ◽  
Technical Note ◽  
Cloud Chemistry ◽  
Bimolecular Reactions ◽  
Kinetic Rate ◽  
First Order Kinetics ◽  
Fractional Cloud ◽  
Kinetics Of

Abstract. The method of entrainment-limited kinetics enables atmospheric chemistry models that do not resolve clouds to simulate heterogeneous (surface and multiphase) cloud chemistry more accurately and efficiently than previous numerical methods. The method, which was previously described for reactions with first-order kinetics in clouds, incorporates cloud entrainment into the kinetic rate coefficient. This technical note shows how bimolecular reactions with second-order kinetics in clouds can also be treated with entrainment-limited kinetics, enabling efficient simulations of a wider range of cloud chemistry reactions. Accuracy is demonstrated using oxidation of SO2 to S(VI) – a key step in formation of acid rain – as an example. Over a large range of reaction rates, cloud fractions, and initial reactant concentrations, the numerical errors in the entrainment-limited bimolecular reaction rates are typically << 1 % and always < 4 %, which is far smaller than the errors found in several commonly used methods of simulating cloud chemistry with fractional cloud cover.

scholarly journals The influence of pressure on the spontaneous ignition of inflammable gas-air mixtures III—Hexane- and isobutane-air mixtures

1934 ◽  
Vol 146 (856) ◽  
pp. 113-129 ◽  
Keyword(s):  
Critical Pressure ◽  
High Pressures ◽  
Initial Pressure ◽  
Liquid Fuels ◽  
Spontaneous Ignition ◽  
Lower Range ◽  
Ignition Point ◽  
Wide Range ◽  
Temperature Ranges ◽  
Low Pressures

In two recent communications we described the results of investigations into the influence of varying initial pressure up to 15 atmospheres on the spontaneous ignition of butane- and pentane-air mixtures, showing that in each case the ignition were located in two distinct and widely separated temperature ranges, location in the higher range occurring at low pressures and in the lower range at high pressures. Transference of an ignition point from the higher to the lower range occurred sharply, at a critical pressure, which depended upon the hydrocarbon concerned and the composition of its mixture with air. The bearing of these observations upon the problem of knock was also discussed. A wide range of explosive media, comprising mainly the higher hydrocarbons contained in liquid fuels, is now being systematically studied, and the present paper summarizes the results obtained for hexane- and isobutane-air mixtures. So far, our results support the view (also recently endorsed by Neumann and Estrovitch) that the lower group of ignition points is the outcome of the survival and further rapid oxidation of certain intermediate bodies, a process favoured by high pressure. whereas the higher group results from ignitions mainly of the products of their thermal decompositions which are favoured by low pressure.

The kinetics and mechanism of the reactions between carbon monoxide and ruthenium(II) chlorides in solution

1970 ◽  
Vol 48 (23) ◽  
pp. 3613-3618 ◽  
Author(s):  
B. C. Hui ◽  
B. R. James
Keyword(s):  
Carbon Monoxide ◽  
Molecular Nitrogen ◽  
Second Order ◽  
Kinetics And Mechanism ◽  
Gas Uptake ◽  
First Order ◽  
Kinetics Of Formation ◽  
Low Pressures ◽  
Kinetics Of ◽  
Hcl Solution

The kinetics of formation of mono- and dicarbonyl complexes in two successive stages by direct carbonylation of ruthenium(II) chlorides in dimethylacetamide solution have been studied at 65–80° and up to 1 atm CO by gas uptake techniques. Both stages are first order in ruthenium. Formation of the monocarbonyl is independent of CO pressure; dicarbonyl formation is first order in CO at low pressures with the order decreasing towards zero with increasing pressure, and shows an inverse chloride dependence from 0.1–2.0 M added chloride. For both stages, the data are consistent with a mechanism involving predissociation. A similar mechanism is suggested for the corresponding reactions in 3 M HCl solution which had been studied earlier and which showed overall second-order kinetics.Discussion on the related formation of molecular nitrogen complexes of ruthenium(II) is presented.

Sign in / Sign up

Export Citation Format

Share Document