The thermal isomerization of 1.2-dimethyl cyclo propane I. Cis-trans isomerization

1960 ◽  
Vol 257 (1288) ◽  
pp. 122-131 ◽  
Keyword(s):  
Gas Chromatography ◽  
High Pressure ◽  
Order Rate Constant ◽  
Enthalpy Change ◽  
Reaction Vessel ◽  
Unimolecular Reaction ◽  
Arrhenius Parameters ◽  
Geometrical Isomerization ◽  
First Order ◽  
Structural Isomerization

This isomerization has been investigated between 380 and 453 °C. In this temperature range, in an ' aged ’ reaction vessel, cis-trans isomerization occurs as a reversible homogeneous unimolecular reaction. The rates of this geometrical isomerization have been measured and the Arrhenius parameters evaluated. In the case of cis 1. 2 -dimethyl cyclo propane, the rate equation obtained is k ∞ = 10 15.25 exp ( - 59 420 ± 500/ RT ) sec -1 . The values of the equili­brium constant for the reaction have also been determined at various temperatures between 380 and 476 °C, and the value of the enthalpy change calculated. The first-order rate constant begins to decrease at about 16 mm, and has fallen to approximately 70 % of the high-pressure value at 0.1 mm. Occurring simultaneously with the geometrical isomerization is a structural isomerization to yield cis and trans pent-2-ene, 2-methylbut-l-ene and 2-methylbut-2-ene. The geometrical isomerization is considerably faster than the structural isomerization. Approximate values for the Arrhenius parameters relating to the various products of the structural isomerization have been determined. Gas chromatography, by means of a katharometer detector with electronic integration, has been used throughout and has been developed to give a precision of ± 0.5 % in the analysis of the reaction mixtures.

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 THERMAL DECOMPOSITION OF ETHANE: PART II. THE UNIMOLECULAR DECOMPOSITION OF THE ETHANE MOLECULE AND THE ETHYL RADICAL

1966 ◽  
Vol 44 (20) ◽  
pp. 2357-2367 ◽  
Author(s):  
M. C. Lin ◽  
M. H. Back
Keyword(s):  
High Pressure ◽  
Rate Constant ◽  
Order Rate Constant ◽  
Methyl Radicals ◽  
Unimolecular Decomposition ◽  
First Order ◽  
Order Rate ◽  
Ethyl Radical ◽  
Lower Temperature ◽  
Ethyl Radicals

The rate of the elementary dissociation of ethane into two methyl radicals has been measured in its pressure-dependent region at temperatures from 913–999 °K and at pressures from 1–200 mm. The high-pressure first-order rate constant obtained by extrapolation was in agreement with that obtained at lower temperatures,[Formula: see text]Comparison with calculated Kassel curves showed that the best fit of the data was obtained with the Kassel parameter s = 12 ± 1. The high-pressure first-order rate constant for the decomposition of the ethyl radical was obtained by extrapolation of the data reported in Part I, assuming the rate constant for combination of ethyl radicals is independent of temperature.[Formula: see text]From the measured constant for the dissociation of ethane, the rate constant for the combination of methyl radicals was calculated and compared with the values measured in a lower temperature region. Differences in the values of the rate constants and in the shapes of the unimolecular falloff curves are discussed.

Fast reaction kinetics of the binding of bromide to iron(III) studied on a high pressure laser temperature jump apparatus

1979 ◽  
Vol 57 (1) ◽  
pp. 77-82 ◽  
Author(s):  
Brian B. Hasinoff
Keyword(s):  
High Pressure ◽  
Activation Volume ◽  
Temperature Jump ◽  
Ion Pairs ◽  
Order Rate Constant ◽  
Fast Reaction ◽  
First Order ◽  
Laser Temperature Jump ◽  
Kinetics Of ◽  
Inner Sphere Complexes

The kinetics of the binding of Br− to Fe(III) were studied as a function of [H+] and [Br−] on a high pressure laser temperature jump apparatus up to 2.76 kbar. At constant [H+] the pseudo first order rate constant for formation of FeBr2+ showed little dependence on pressure or on [Br−] over the range 0.02 to 1.9 M. The results were interpreted by a mechanism in which Fe3+ and FeOH2+ react with Br− to form ion pairs prior to formation of their inner sphere complexes. The kinetic activation volume for the conversion of the Fe3+, Br− ion pair to FeBr2+ appears to be quite negative, consistent with an associative interchange (Ia) mechanism.

Thermal decomposition of di-tert-butyl peroxide at high pressure

1968 ◽  
Vol 46 (16) ◽  
pp. 2721-2724 ◽  
Author(s):  
D. H. Shaw ◽  
H. O. Pritchard
Keyword(s):  
Carbon Dioxide ◽  
Thermal Decomposition ◽  
High Pressure ◽  
Shock Tube ◽  
Total Pressure ◽  
Order Rate Constant ◽  
Kcal Mole ◽  
First Order ◽  
Tert Butyl ◽  
Butyl Peroxide

The thermal decomposition of di-tert-butyl peroxide has been studied in the presence of carbon dioxide at total pressures from 0.05 to 15 atm and temperatures from 90–130 °C. The first-order rate constant for the decomposition is independent of total pressure in this range, with Arrhenius parameters E = 37.8 ± 0.3 kcal/mole and log A(s−1) = 15.8+0.2. A reevaluation of previous data on this reaction leads us to recommend E = 37.78 ± 0.06 kcal/mole and log A(s−1) = 15.80 ± 0.03 over the temperature range 90–350 °C; extension of this range to higher temperatures using a shock tube would be worthwhile.

The thermal isomerization of 1. 2-dimethyl cyclo propane II. Structural isomerization

1961 ◽  
Vol 260 (1302) ◽  
pp. 424-432 ◽  
Keyword(s):  
Transition State ◽  
Thermal Isomerization ◽  
Reaction Vessel ◽  
Rate Equations ◽  
Arrhenius Parameters ◽  
Temperature Range ◽  
Structural Isomerization ◽  
Electronic Integration ◽  
Ring Transition State

This isomerization has been investigated between 434 and 475 °C. In this temperature range, in an ‘aged’ reaction vessel, the structural isomerization from either cis or trans 1. 2-dimethyl cyclo propane occurs as a unimolecular transformation which is slower than the reversible cis-trans isomerization. The products of the reaction are 2-methylbut-1-ene, 2-methylbut-2-ene and cis and trans pent-2-ene. The rates of formation of these compounds have been measured and the Arrhenius parameters evaluated. The rate equations for the formation of 2-methylbut-1-ene and 2-methylbut-2-ene are k ∞ = 10 13.93 exp(-61900/ RT ) S -1 and 10 14.08 exp (-62300/ RT ) S -1 respectively and are the same for their production from either the cis or the trans dimethyl cyclo propane. The pent-2-enes are formed more rapidly from cis 1. 2-dimethy cyclo propane than from the trans compound. From cis 1.2-dimethyl cyclo propane cis and trans pent-2-ene are formed at rates given by the equations k ∞ = 10 13.92 exp (-61400/ RT )s -1 and 10 13.96 exp (-61200/ RT )s -1 , respectively. From trans 1.2-dimethyl cyclo propane the rate equations are k ∞ = 10 14.40 exp (-63600/ RT )s -1 and 10 14.30 exp (-62900/ RT )s -1 . The possible mechanisms for both the geometrical and structural isomerizations have been discussed and it has been concluded than an ‘expanded ring’ transition state gives a satis­factory explanation of the results obtained. It is also suggested that this strengthens the case for a similar mechanism in the case of the isomerization of cyclo propane. Gas chromato­graphy, by means of a katharometer detector with electronic integration, has been used throughout and has been developed to give a precision of ±0.5% in the analysis of the reaction mixtures.

Development of Sustained Release Multi-Component Microparticulate System of Diclofenac Sodium and Tizanidine Hydrochloride

1970 ◽  
Vol 1 (1) ◽  
pp. 97-105
Author(s):  
Kamlesh Dashora ◽  
Shailendra Saraf ◽  
Swarnalata Saraf
Keyword(s):  
Particle Size ◽  
Sustained Release ◽  
Cellulose Acetate ◽  
Rate Constant ◽  
Diclofenac Sodium ◽  
Order Rate Constant ◽  
Anomalous Transport ◽  
First Order ◽  
Sem Study ◽  
Transport Type

Sustained released tablets of diclofenac sodium (DIC) and tizanidine hydrochloride (TIZ) were prepared by using different proportions of cellulose acetate (CA) as the retardant material. Nine formulations of tablets having different proportion of microparticles developed by varied proportions of polymer: drug ratio ‘’i.e.’’; 1:9 -1:3 for DIC and 1:1 – 3:1 for TIZ. Each tablet contained equivalent to 100 mg of DIC and 6mg of TIZ. The prepared microparticles were white, free flowing and spherical in shape (SEM study), with  the particle size varying from 78.8±1.94 to 103.33±1.28 µm and 175.92± 9.82 to 194.94±14.28µm for DIC  and TIZ, respectively.  The first order rate constant K1 of formulations were found to be in the range of  K1 = 0.117-0.272 and 0.083- 0.189 %hr-1for DIC and TIZ, respectively. The value of exponent coefficient (n) was found to be in the range of 0.6328-0.9412  and 0.8589-1.1954 for DIC and TIZ respectively indicates anomalous  to  non anomalous transport type of diffusions among different formulations

Kinetics of bioactive compounds in functional spice Jiangpo during thermal processing

2012 ◽  
Vol 8 (3) ◽  
Author(s):  
Xiaoyan Dai ◽  
Chenhuan Yu ◽  
Qiaofeng Wu
Keyword(s):  
Kinetic Parameters ◽  
Bioactive Compounds ◽  
Thermal Processing ◽  
Order Rate Constant ◽  
Heat Processing ◽  
Order Kinetic ◽  
Time Intervals ◽  
First Order ◽  
Order Kinetic Model ◽  
Kinetics Of

Abstract Jiangpo is an increasingly popular East Asian spice which is made from Mangnolia officinalis bark and ginger juice. Since it induces bioactive compounds decomposition and has influence on final flavor and fragrance, cooking is regarded as the key operation in preparation of Jiangpo. To evaluate the bioactive compounds content changes of Jiangpo during thermal processing, kinetic parameters including reaction order, rate constant, T1/2 and activation energy of bioactive markers namely honokiol, magnolol and curcumin were determined. Cooking was set at temperatures 60, 90 and 120 °C for selected time intervals. Results displayed the thermal kinetic characteristics of the three compounds. Thermal degradation of Honokiol and magnolol both followed first order kinetic model and the loss of curcumin fitted second order. A mathematical model based on the obtained kinetic parameters has also been developed to predict the degradation of honokiol, magnolol and curcumin in non-isothermal state. All the information in this paper could contribute necessary information for optimizing the existing heat processing of Jiangpo.

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