Kinetics of neopentyl chloride pyrolysis. II. The radical-chain decomposition

1968 ◽  
Vol 46 (8) ◽  
pp. 1351-1359 ◽  
Author(s):  
J. S. Shapiro ◽  
E. S. Swinbourne
Keyword(s):  
Rate Coefficient ◽  
Surface Effect ◽  
High Surface ◽  
Volume Ratio ◽  
Unimolecular Decomposition ◽  
Radical Chain ◽  
Small Surface ◽  
First Order ◽  
Initiation Step ◽  
Kinetics Of

The radical-chain thermal decomposition of neopentyl chloride was studied in the temperature range of 410–496 °C and over the pressure range of 22 to 340 mm. A small surface effect was noted after prolonged conditioning of the vessel and in a vessel of high surface/volume ratio. The reaction is of three-halves order and the rate coefficient is expressible by k3/2 (11/2 mole−1/2 s−1) = 1013.55 ± 0.67 × e−56300 ± 2100/RT. The experimental facts are shown to be consistent with a mechanism involving chlorine atoms as the principal propagating radicals, with a first-order initiation step and a termination step involving the combination of methyl and chloromethyl radicals. The relative concentrations of the various radicals, calculated from known and estimated kinetic parameters, have been shown to be dependent on the hydrogen chloride produced from the concurrent unimolecular decomposition of neopentyl chloride reported in Part I. 1,1-Dimethylcyclopropane, found as a reaction product, is believed to be formed directly from neopentyl chloride by a radical-chain mechanism.

The kinetics of the thermal decomposition of trifluoroacetaldehyde

1965 ◽  
Vol 18 (10) ◽  
pp. 1561 ◽  
Author(s):  
NL Arthur ◽  
TN Bell
Keyword(s):  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Rate Equation ◽  
Surface Effect ◽  
Inert Gases ◽  
Radical Chain ◽  
Small Surface ◽  
Experimental Rate ◽  
Products Of Reaction ◽  
Kinetics Of

The thermal decomposition of trifluoroacetaldehyde has been studied at temperatures between 471� and 519�, and at pressures up to 180 mm. The main products of reaction are trifluoromethane and carbon monoxide in equal amounts; small amounts of hexafluoroethane and hydrogen are also formed. The experimental rate equation governing the observed kinetics is of the form Rate = k?[CF3CHO]3/2, where k? = 1012.2exp(-49000/RT) l.� mole-1 sec-1 A small surface effect is apparent, an increase in surface area causing an increase in rate. Inert gases, namely carbon monoxide and dioxide, increase the rate of decomposition, the experimental rate equation assuming the form Rate = (k'[CF3CHO]3 + k"[CF3CHO]2.2[M])� A mechanism is proposed which predict,^ the experimental form of the rate equation and involves initiation through a second-order energy transfer process followed by a radical chain mechanism, the length of which is 1200 with P(CF3CHO) = 200 mm. Termination is considered to be through the third-order recombination of trifluoromethyl radicals.

Kinetics of aquation of the fluoropentaamminecobalt(III) ion

1970 ◽  
Vol 48 (7) ◽  
pp. 1054-1058 ◽  
Author(s):  
T. W. Swaddle ◽  
W. E. Jones
Keyword(s):  
Ionic Strength ◽  
Rate Coefficient ◽  
Hydrogen Ion ◽  
Fluoride Ion ◽  
Kcal Mole ◽  
First Order ◽  
Order Rate ◽  
Relationship Of ◽  
The Relationship ◽  
Kinetics Of

The kinetics of the hydrogen-ion-independent pathway for the replacement of fluoride in aqueous (NH3)5CoF2+ by H2O have been reinvestigated using a specific fluoride-ion electrode, with due regard for the concomitant autocatalytic loss of the ammine ligands. In perchlorate media of ionic strength 0.1 M, the first-order rate coefficient is 1.22 × 10−6 s−1 at 45°, and the kinetics are represented by ΔH* = 24.4 kcal mole−1 and ΔS* = −9 cal deg−1 mole−1 over the range 35–75° at least. The relationship of these data to those for the aquation of other species of the type ML5Xn+ is discussed.

The kinetics of the pyrolysis of Cyclohexyl chloride.

1958 ◽  
Vol 11 (3) ◽  
pp. 314 ◽  
Author(s):  
ES Swinbourne
Keyword(s):  
Gas Phase ◽  
Hydrogen Chloride ◽  
Rate Coefficient ◽  
Initial Pressure ◽  
Order Reaction ◽  
Rate Coefficients ◽  
Homogeneous Reaction ◽  
First Order ◽  
Induction Periods ◽  
Kinetics Of

cycloHexy1 chloride has been shown to decompose in the gas phase at 318-385 �C almost exclusively to cyclohexene and hydrogen chloride. With clean glass-walled reactors the reaction was largely heterogeneous, but after the walls were coated with a carbonaceous film a homogeneous first-order reaction was found to predominate. For initial pressures within the range 4-40 cm mercury the rate coefficients for the homogeneous reaction were expressible as������� k = 5.88 x 1013exp(-50,000 cal/RT) sec-1. There was some evidence for the rate coefficient becoming pressure-dependent below 5-10 mm initial pressure of reactant. The reaction exhibited no induction periods and the velocity was virtually unaffected by the addition of large amounts of propene or cyclohexene and traces of chlorine or bromine. The results were consistent with a unimolecular elimination of hydrogen chloride.

Kinetics of the thermal reactions of ethylene. Part II. Ethylene–ethane mixtures

1968 ◽  
Vol 46 (14) ◽  
pp. 2427-2433 ◽  
Author(s):  
M. L. Boyd ◽  
M. H. Back
Keyword(s):  
Free Radical ◽  
Product Formation ◽  
Radical Chain ◽  
Thermal Reactions ◽  
Temperature Range ◽  
Initiation Step ◽  
Chain Polymerization ◽  
Main Effects ◽  
Kinetics Of ◽  
Simplified Mechanism

Mixtures of ethane and ethylene have been pyrolyzed in the temperature range 563–600 °C and at pressures from 30–60 cm. The products were similar to those obtained from the pyrolysis of ethylene by itself, described m Part I, with a marked increase in the yields of the saturated products. The initial rates of product formation and the dependence of these rates on the concentration of ethane suggest that the initiation step is the same as that proposed in the pyrolysis of ethylene alone, viz.[Formula: see text]and that the reaction[Formula: see text]is not an important source of radicals. A simplified mechanism is outlined to account for the main effects of ethane on the free radical chain polymerization.

scholarly journals THE THERMAL UNIMOLECULAR ISOMERIZATION OF 1,2-DICHLOROETHYLENE

1966 ◽  
Vol 44 (18) ◽  
pp. 2143-2148 ◽  
Author(s):  
L. D. Hawton ◽  
G. P. Semeluk
Keyword(s):  
Volume Ratio ◽  
No Decomposition ◽  
Radical Scavenger ◽  
Radical Chain ◽  
Limits Of Detection ◽  
First Order ◽  
First Order Kinetics ◽  
Trans Isomerization ◽  
Conversion Formula

The thermal cis–trans isomerization of 1,2-dichloroethylene in a toluene carrier was found to follow first order kinetics at temperatures below 846 °K. Within the limits of detection, no decomposition was observed, but there was evidence of a surface contribution to the isomerization. The results, extrapolated to a surface to volume ratio of zero, give for the cis to trans conversion[Formula: see text]and for the reverse action[Formula: see text]It is concluded that previous investigations which did not use a radical scavenger most probably were observations of a mixture of radical chain, heterogeneous, and unimolecular contributions to the isomerization.

The thermal decomposition of trimethylacetyl bromide

1970 ◽  
Vol 23 (3) ◽  
pp. 525 ◽  
Author(s):  
BS Lennon ◽  
VR Stimson
Keyword(s):  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Hydrogen Bromide ◽  
Transition States ◽  
Volume Ratio ◽  
Reaction Vessel ◽  
Chain Mechanism ◽  
Radical Chain ◽  
First Order ◽  
Polar Transition

Trimethylacetyl bromide decomposes at 298-364� into isobutene, carbon monoxide, and hydrogen bromide in a first-order manner with rate given by k1 = 138 x 1014exp(-48920/RT) sec-1 The rate is unaffected by addition of the products or of inhibitors, or by increase of the surface/volume ratio of the reaction vessel. The likely radical chain mechanism is considered and rejected. The reaction is believed to be a molecular one, and possible cyclic and polar transition states are discussed.

scholarly journals Size Also Matters in Biodegradable Composite Microfiber Reinforced by Chitosan Nanofibers

2014 ◽  
Vol 1621 ◽  
pp. 59-69
Author(s):  
Elisabete D. Pinho ◽  
Albino Martins ◽  
José V. Araújo ◽  
Rui L. Reis ◽  
Nuno M. Neves
Keyword(s):  
Biomedical Applications ◽  
High Surface ◽  
High Surface Area ◽  
Volume Ratio ◽  
Electrospun Nanofibers ◽  
Butylene Succinate ◽  
Biodegradable Composite ◽  
Biological Performance ◽  
Different Diameters ◽  
Kinetics Of

ABSTRACTPioneer works on nanocomposites were focused in carbon nanofibers or nanotubes dispersed in epoxy matrix, a viscous liquid facilitating the compounding stage. The interest in developing new composites aimed for biomedical applications led us to design new nanocomposites based in biodegradable polymers with demonstrated biological performance.We report herein the development of micro-nano composites by extruding poly(butylene succinate) (PBS) microfibers with two different diameters, 200 and 500 µm, reinforced with electrospun chitosan nanofibers. Analysis of the microfibers showed high levels of alignment of the reinforcing phase and excellent distribution of the nanofibers in the composite. Its geometry facilitates the development of orthotropy, maximizing the reinforcement in the axial fiber main axis.The biodegradable microfiber composites show an outstanding improvement of mechanical properties and of the kinetics of biodegradation, with very small fractions (0.05 and 0.1 wt.%) of electrospun chitosan nanofibers reinforcement. The high surface area-to-volume ratio of electrospun nanofibers combined with the increased water uptake capability of chitosan justify the accelerated kinetics of biodegradation of the composite as compared with the unfilled synthetic polymer.

scholarly journals Second messenger molecules have a limited spread in olfactory cilia

2018 ◽  
Vol 150 (12) ◽  
pp. 1647-1659 ◽  
Author(s):  
Hiroko Takeuchi ◽  
Takashi Kurahashi
Keyword(s):  
Molecular Diffusion ◽  
High Surface ◽  
Olfactory Receptors ◽  
Volume Ratio ◽  
Second Messenger ◽  
Limited Information ◽  
Olfactory Cilia ◽  
Integer Multiple ◽  
Messenger Molecules ◽  
Kinetics Of

Odorants are detected by olfactory receptors on the sensory cilia of olfactory receptor cells (ORCs). These cylindrical cilia have a diameters of 100–200 nm, within which the components required for signal transduction by the adenylyl cyclase–cAMP system are located. The kinetics of odorant responses are determined by the lifetimes of active proteins as well as the production, diffusion, and extrusion/degradation of second messenger molecules (cAMP and Ca2+). However, there is limited information about the molecular kinetics of ORC responses, mostly because of the technical limitations involved in studying such narrow spaces and fine structures. In this study, using a combination of electrophysiology, photolysis of caged substances, and spot UV laser stimulation, we show that second messenger molecules work only in the vicinity of their site of generation in the olfactory cilia. Such limited spreading clearly explains a unique feature of ORCs, namely, the integer multiple of unitary events that they display in low Ca2+ conditions. Although the small ORC uses cAMP and Ca2+ for various functions in different regions of the cell, these substances seem to operate only in the compartment that has been activated by the appropriate stimulus. We also show that these substances remain in the same vicinity for a long time. This enables the ORC to amplify the odorant signal and extend the lifetime of Ca2+-dependent adaptation. Cytoplasmic buffers and extrusion/degradation systems seem to play a crucial role in limiting molecular spreading. In addition, binding sites on the cytoplasmic surface of the plasma membrane may limit molecular diffusion in such a narrow space because of the high surface/volume ratio. Such efficient energy conversion may also be broadly used in other biological systems that have not yet been subjected to systematic experiments.

scholarly journals Effects of Nanoparticles on properties of Self Compacting Concrete (SCC) and Self Compacting Mortar (SCM)

2019 ◽  
Vol 8 (3) ◽  
pp. 2977-2979
Keyword(s):  
Construction Industry ◽  
Surface Effect ◽  
High Surface ◽  
Volume Ratio ◽  
Recent Time ◽  
Nano Particles ◽  
Gel Formation ◽  
Self Compacting Concrete ◽  
Research Areas ◽  
Insight Into

Nanotechnology is the most attractive research areas because of its useful applications that have gradually recognized itself in the recent time. Nanoparticles are potential materials in construction industry. Nanoparticles have excellent properties and high surface-to-volume ratio, are known to improve the microstructure of concrete, accelerate the CSH gel formation, and improve the properties of concrete. This study aims to understand the properties of self-compacting concrete (SCC) containing nanoparticles such as nano SiO2, TiO2, ZrO2, CuO. Influence of nano particles to SCC and SCM has received extensive interest from both researchers and construction industry due to their interface improving effect, surface effect and smaller size. This study significantly reviews recent research carried out on the influence of Nano particles on properties of both SCC and SCM. Detailed review on the fresh, strength, microstructural and durability properties of Self Compacting Concrete containing Nano particles are presented. This paper also aims to provide a widespread knowledge insight into possible application of Nanopartices on SCC and SCM in the construction industry. Keywords: Nanotechnology, nanoparticles, CSH gel formati

Kinetics and mechanisms of the thermal decomposition of propane II. The reaction inhibited by nitric oxide

1962 ◽  
Vol 270 (1341) ◽  
pp. 254-266 ◽  
Keyword(s):  
Nitric Oxide ◽  
Volume Ratio ◽  
Inflexion Point ◽  
Kcal Mole ◽  
Large Excess ◽  
First Order ◽  
Partial Pressures ◽  
Pressure Time ◽  
Initiation Reaction ◽  
Kinetics Of

The kinetics of the pyrolysis of propane inhibited by nitric oxide were investigated from 640 to 560 °C and at partial pressures of propane from 25 to 550 mm Hg. The pressure-time curves were found to be S-shaped, and the induction period was lengthened considerably as the propane pressure was lowered. Complete inhibition by nitric oxide was obtained with 10 to 12% nitric oxide. The initial rates were found to be proportional to the 3/2 power of the pressure over most of the temperature range, and to a slightly lower power at the highest temperatures. The orders of reaction corresponding to the inflexion point are close to unity at the highest temperatures, and increase steadily as the temperature is lowered. The activation energy calculated from the inflexion rates in the first-order region was 69.4 kcal/ mole. The rates decreased with an increase in the surface to volume ratio. The addition of a large excess of carbon dioxide had no effect on the fully inhibited rates. The results are shown to be consistent with a mechanism in which the initiation reaction involves the abstraction of a hydrogen atom from propane by nitric oxide, and in which the termination reaction is between HNO and a propyl radical.

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