CW-CO2 laser-induced and SF6-sensitized decomposition of trifluoroacetic acid

1981 ◽  
Vol 46 (11) ◽  
pp. 2854-2859 ◽  
Author(s):  
Josef Pola
Keyword(s):  
Trifluoroacetic Acid ◽  
Surface Reaction ◽  
Reaction Scheme ◽  
Conventional Heating ◽  
Reaction Products ◽  
First Order ◽  
Cw Co2 Laser ◽  
Kinetics Of ◽  
Induced Reaction ◽  
Carbonyl Fluoride

CW-CO2 laser-induced and SF6-sensitized decomposition of trifluoroacetic acid affords reaction products different from those yielded by a conventional heating and offers a new way for decomposition of this compound. The kinetics of the laser-induced reaction is also different, being of a second order and of a first order in SF6. The reaction scheme proposed for the laser-induced process shows .CF2CO2. biradical to be mainly decomposed to carbon monoxide and carbonyl fluoride and implies that the fate of this species during conventional thermal decomposition is controlled by heterogeneous surface reaction.

CW-CO2 laser-induced and SF6-sensitized decomposition of trifluoroacetic anhydride

1981 ◽  
Vol 46 (11) ◽  
pp. 2860-2864 ◽  
Author(s):  
Josef Pola
Keyword(s):  
Thermal Stability ◽  
Trifluoroacetic Acid ◽  
Heterogeneous Reaction ◽  
Thermal Conditions ◽  
Trifluoroacetic Anhydride ◽  
Conventional Heating ◽  
Kinetics Of ◽  
Relative Thermal Stability ◽  
Induced Reaction ◽  
Carbonyl Fluoride

CW-CO2 laser-induced and SF6-sensitized decomposition of trifluoroacetic anhydride affords carbonyl fluoride, carbon monoxide and trifluoroacetyl fluoride, the products different from those given by a conventional heating. The products and the kinetics of the laser-induced reaction reflect a different behaviour of presumably formed transient .CF2CO2. biradical under conditions precluding heterogeneous reaction on the reactor walls and point out that the fate of the .CF2CO2. species formed during the laser-powered homogeneous pyrolysis of trifluoroacetic acid and that of trifluoroacetic anhydride is under these conditions identical. The reverse order of thermal stability for trifluoroacetic acid and trifluoroacetic anhydride observed during the conventional and laser-induced pyrolysis suggests the laser-powered homogeneous process as a tool for modification of compounds' (relative) thermal stability ascertained under conventional thermal conditions including participation of heterogeneous surface reactions.

scholarly journals Frequency Dependent Kinetics of the CW CO2 Laser Induced Reaction of CF3CF2Cl

1987 ◽  
Vol 7 (5-6) ◽  
pp. 271-277
Author(s):  
R. N. Zitter ◽  
D. F. Koster ◽  
N. Siddiqua
Keyword(s):  
Activation Energy ◽  
Absorption Band ◽  
Co2 Laser ◽  
Laser Frequency ◽  
Kcal Mole ◽  
Band Center ◽  
Laser Frequencies ◽  
Cw Co2 Laser ◽  
Kinetics Of ◽  
Induced Reaction

Kinetics of the decomposition of CF3CF2Cl at 50 torr by a cw CO2 laser have been studied over a range of laser frequencies extending 36 cm−1 below an absorption band center at 980 cm−1. At constant translational temperature, the change in the rate constant with laser frequency is a factor of 100, comparable to the effect previously observed in CF2ClCF2Cl. Arrhenius plots show an activation energy of 86.2 kcal/mole, independent of frequency.

KINETICS OF CATALYTIC REACTIONS ON A UNIFORM SURFACE AND SINGLE SITES: SIMILARITY AND DIFFERENCE

2009 ◽  
Vol 16 (05) ◽  
pp. 757-760 ◽  
Author(s):  
VLADIMIR P. ZHDANOV
Keyword(s):  
Reaction Scheme ◽  
Catalytic Reactions ◽  
First Order ◽  
Metal Atoms ◽  
Catalytic Sites ◽  
Reaction Orders ◽  
Similarities And Differences ◽  
Similarity And Difference ◽  
Kinetics Of ◽  
Kinetics Of Catalytic Reactions

To illustrate typical similarities and differences in the reaction kinetics occurring on a uniform surface and single sites (e.g. on single metal atoms incorporated into the inner walls of zeolite), we analyze a generic reaction scheme of N2O decomposition running in the presence of oxygen. In both cases, there are three reaction regimes, (i) controlled exclusively by the N2O -decomposition step, (ii) partly inhibited by oxygen, or (iii) limited by oxygen desorption. Regime (i) is kinetically similar (first order in N2O ) in the two cases. The states of the catalytic sites are however different. Regime (ii) exhibits different reaction orders in oxygen (-0.5 for the surface and -1 for single sites). Regime (iii) is fully identical in both the cases.

Frequency dependent kinetics of the cw CO2 laser induced reaction of CF3Br

1986 ◽  
Vol 59 (4) ◽  
pp. 259-262 ◽  
Author(s):  
R.N. Zitter ◽  
D.F. Koster ◽  
M.S. Parvez
Keyword(s):  
Co2 Laser ◽  
Frequency Dependent ◽  
Cw Co2 Laser ◽  
Kinetics Of ◽  
Induced Reaction

The thermal decomposition of diethyl ether. III. The action of inhibitors and the mechanism of the reaction

1958 ◽  
Vol 245 (1240) ◽  
pp. 49-67 ◽  
Keyword(s):  
Nitric Oxide ◽  
Thermal Decomposition ◽  
Diethyl Ether ◽  
Rate Constant ◽  
Initial Pressure ◽  
Direct Analysis ◽  
Reaction Products ◽  
First Order ◽  
Molecular Decomposition ◽  
Induced Reaction

Small quantities of nitric oxide reduce the rate of thermal decomposition of diethyl ether at 525 °C to about one-quarter. Much larger amounts accelerate the decomposition, but the concentration ranges in which the ‘ maximally inhibited ’ reaction and the ‘ nitric-oxide-induced’ reaction can be studied are so widely separated that these reactions can be treated as two distinct entities. The ‘uninhibited’ reaction constitutes a third. Reaction products and kinetics are recorded for all three, and nitric oxide consumption is measured for the first two. In all three the major products are the same, with secondary differences which are discussed. In the presence of nitric oxide small amounts of cyanides and other compounds are formed. In the nitric-oxide-induced reaction 1.4 molecules of ether are decomposed for each molecule of nitric oxide used up: in the maximally inhibited reaction the ratio, which is dependent on the ether pressure, is very much greater. The rate of the maximally inhibited reaction is independent of the concentration of nitric oxide, or of propylene, and the same for the two inhibitors (as is now proved by direct analysis). The first-order rate constant varies with the initial pressure of ether according to the equation k inhib. = ( A [ether])/(1 + B [ether]) + C [ether]. The rate constant of the uninhibited reaction varies with ether pressure according to an expression which, although probably of different algebraical form, is empirically similar to the above over a considerable range. The nitric-oxide-induced reaction is nearly of the first order with respect both to ether pressure and to nitric oxide pressure. The maximally inhibited reaction is shown to be most probably a molecular decomposition of the ether. The uninhibited reaction is predominantly a chain reaction, the mechanism of which is discussed. The nitric-oxide-induced reaction, it is suggested on the basis of the experimental evidence, is largely initiated by a generation of radicals in an attack of nitric oxide on ether. It is possibly also in part a molecular decomposition of ether caused by collision with nitric oxide.

Eigenanalysis of the Coupled First-Order Isomerization Reactions of the Bis[(S)-alaninato]dinitrocobaltate(III) Ion

1989 ◽  
Vol 42 (10) ◽  
pp. 1647
Author(s):  
JK Beattie ◽  
MB Celap ◽  
MT Kelso ◽  
SM Nesic
Keyword(s):  
Differential Equations ◽  
Aqueous Solutions ◽  
Rate Constants ◽  
Chromatographic Separation ◽  
Reaction Scheme ◽  
Isomerization Reaction ◽  
Geometric Isomers ◽  
First Order ◽  
Kinetics Of ◽  
First Order Differential Equations

Three of the five possible geometric isomers of the bis[(S)-alaninato] dinitrocobaltate (III) ion isomerize to the stable fourth isomer by a series of first-order reactions. The fifth isomer is not observed. The kinetics of the isomerizations in neutral, aqueous solutions between 65 and 95 C have been studied by chromatographic separation of the isomers. The data were fitted by eigenanalysis of the coupled first-order differential equations. The results are consistent with a reaction scheme requiring five rate constants, kxy, where xy represents isomerization from isomer x to isomer y. lsomer A is the Λ-(-)589-cis-NO2/cis-N/cis-O complex; isomer B the trans-NO2/cis-N/cis-O complex; isomer C the trans-NO2/trans-N/trans-O complex; and isomer D is the mixture of both diastereomers of the cis-NO2/trans-N/cis-O complex that is formed from B and C. The rate constants required are kAB, kbc , kBD , kCB and kCD . The same reaction scheme had been found previously for the analogous glycinato complexes, but the activation energies differ. For the valine and leucine analogues, the rate constants and activation enthalpies for the first isomerization reaction, represented by kAB, are similar to that of the alanine complex.

Carbonyl fluoride formation by cw-CO2 laser-induced and sulfur hexafluoride-sensitized decomposition of hexafluoroacetone

1981 ◽  
Vol 46 (5) ◽  
pp. 1254-1257 ◽  
Author(s):  
Josef Pola ◽  
Pavel Engst ◽  
Milan Horák
Keyword(s):  
Gas Phase ◽  
Co2 Laser ◽  
Sulfur Hexafluoride ◽  
Phase Decomposition ◽  
First Order ◽  
First Order Kinetics ◽  
Cw Co2 Laser ◽  
Carbonyl Fluoride

The cw-CO2 laser-induced gas phase decomposition of hexafluoroacetone sensitized with sulfur hexafluoride (both 0.7-5.2 kPa) affords, besides perfluorinated hydrocarbons and minor amounts of trifluoroacetyl fluoride, carbonyl fluoride the formation of that obeys first-order kinetics and is favored with higher SF6 content.

Vulcanization of Elastomers. 30. Kinetics of the Decrease of Sulfur Concentration during Vulcanization

1961 ◽  
Vol 34 (2) ◽  
pp. 606-628 ◽  
Author(s):  
Walter Scheele ◽  
Martin Cherubim
Keyword(s):  
Initial Rate ◽  
Order Reaction ◽  
Usual Sense ◽  
Complex Nature ◽  
Reaction Products ◽  
Sulfur Concentration ◽  
First Order ◽  
Synthetic Rubber ◽  
Kinetics Of ◽  
Characteristic Trend

Abstract The present discussion deals with the explanation and critical analysis of the kinetics of the decrease in concentration of sulfur in accelerated and unaccelerated vulcanizations of natural and synthetic rubber. A marked distinction is made between the time law and the dependence on concentration of the rate of decrease of sulfur, since there is lack of agreement between them, both in accelerated and unaccelerated vulcanizations, which indicates the complex nature of vulcanization. In unaccelerated vulcanization, the sulfur concentration drops, at all temperatures and independent of the concentration, according to a time law with exponent n=0.6. On the other hand, the dependence on concentration of the initial rate of sulfur decrease proceeds according to a first order reaction. These relations make it seem probable that sulfur decrease involves a process which is catalyzed by reaction products. In accelerated vulcanization, the reduction of concentration of sulfur also is expressed by a time law with the exponent n<1, and this too is independent of temperature and concentration of reactants (sulfur and accelerator). However, the concentration dependence of the rate of sulfur decrease cannot be expressed by a power law, so that we find no order of reaction in the usual sense. We attempt to explain the characteristic trend of the initial rate of sulfur decrease with sulfur concentration at constant accelerator content, or with accelerator concentration at constant sulfur content, by assuming that the vulcanization takes place through intermediate compounds. The pertinent theoretical conceptions are disclosed and critically examined and the attempt is made to show the extent to which they may be brought into accord with the experimental data.

scholarly journals Effects of Microwave Irradiation on Activation Energy and Reaction Rate of Synthesis of Dodecylmethyldihydroxyl Ammonium Bromide

2011 ◽  
Vol 396-398 ◽  
pp. 1044-1047 ◽  
Author(s):  
Tao Yan Mao ◽  
Cheng Zheng ◽  
Jimmy Yu
Keyword(s):  
Activation Energy ◽  
Microwave Irradiation ◽  
Reaction Rate ◽  
Conventional Heating ◽  
Irradiation Condition ◽  
Ammonium Bromide ◽  
Reaction Conditions ◽  
First Order ◽  
Conventional Condition ◽  
Kinetics Of

The reaction kinetics of the synthesis of quaternary ammonium salt under two sets of different reaction conditions, including microwave irradiation condition and conventional heating condition, were studied. In order to make sure that the microwave would not be interrupted, the reaction temperature was maintained at the boiling point of reaction solvents. The results showed that the reaction was a first-order reaction under both set of conditions and microwave irradiation changed the value of the activation energy of the reaction, indicating a change in the reaction mechanism. The activation energy was 41.44 kJ/mol under microwave irradiation condition, and 61.21 kJ/mol under conventional condition.

Studies in polymerization - VII. The polymerization of N -carboxy-α-amino acid anhydrides

1954 ◽  
Vol 223 (1155) ◽  
pp. 495-520 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Amino Acid ◽  
Reaction Scheme ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
First Order ◽  
Molecular Weights ◽  
Rate Determining Step ◽  
Acid Anhydrides ◽  
Kinetics Of

The kinetics of the polymerization of the N -carbonic anhydrides of DL-leucine, DL-phenylalanine and sarcosine in nitrobenzene solution have been studied. When preformed polymer is used as initiator, and in the complete absence of water, the first two anhydrides polymerize at rates which show first-order dependence on the monomer (anhydride) and initiator con­centrations. The reaction of the sarcosine derivative, however, while first order in monomer, is very nearly second order in initiator, and is strongly catalyzed by carbon dioxide. This latter effect is attributed to the substituted carbamic acids formed by interaction of carbon dioxide and bases in the system. Other acids have been shown to be catalysts for the reaction. The observations are consistent with a reaction scheme (5) in which a complex is formed reversibly from the monomer and a base; this complex may then decompose with evolution of carbon dioxide by routes involving base or acid catalysis. The polymerizations of the DL-leucine and DL-phenylalanine carbonic anhydrides are simple cases of this reaction mechanism in which the formation of the complex is the rate-determining step. This difference explains the lower order of these reactions in the initiator concentration, the absence of catalysis, and also the observation that unlike the formation of polysarcosine these polymerizations have a positive temperature coefficient. When the dimethylamide of an amino-acid is used as initiator the first stage of the reaction is faster than the subsequent stages involving polymers, since the initiator is a stronger base than the polymers. The kinetics for these reactions have been worked out, and shown to agree with experiment. The tertiary bases pyridine and quinoline when quite pure have been shown to be ineffective as initiators of the polymerization of sarcosine carbonic anhydride. Initiation by water and amino-acids is discussed. The molecular weights and molecular weight distribution are not affected by the presence of acid catalysts. The distribution for a reaction in which the first step has a rate different from that of the subsequent ones has been calculated.

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