scholarly journals Norbornadiene as a Universal Substrate for Organic and Petrochemical Synthesis

2017 ◽  
Vol 3 (2) ◽  
pp. 73 ◽  
Author(s):  
V.R. Flid ◽  
O.S. Manulik ◽  
D.V. Dmitriev ◽  
V.B. Kouznetsov ◽  
E.M. Evstigneeva ◽  
...  
Keyword(s):  
Reaction Rate ◽  
Double Bonds ◽  
Polycyclic Hydrocarbons ◽  
Petrochemical Synthesis ◽  
Unsaturated Compounds ◽  
Wide Range ◽  
Catalytic Processes ◽  
Universal Substrate

A wide range of rare polycyclic hydrocarbons can be obtained through catalytic processes involving norbornadiene (NBD). The problem of selectivity is crucial for such reactions. The feasibility of controlling<br />selectivity and reaction rate has been shown for cyclic dimerization, co-dimerization, isomerization and allylation of NBD. Kinetic rules have been scrutinized. Consistent mechanisms have been proposed. Factors<br />affecting directions of the reactions and allowing us to obtain individual stereoisomers quantitatively, have been established. A series of novel unsaturated compounds has been synthesized; they incorporate a<br />set of double bonds with different reactivity and can find an extremely wide range of applications.

scholarly journals Selective synthesis of thioethers in the presence of a transition-metal-free solid Lewis acid

2016 ◽  
Vol 12 ◽  
pp. 2627-2635 ◽  
Author(s):  
Federica Santoro ◽  
Matteo Mariani ◽  
Federica Zaccheria ◽  
Rinaldo Psaro ◽  
Nicoletta Ravasio
Keyword(s):  
Reaction Rate ◽  
Solid Acid ◽  
Amorphous Solid ◽  
Solid Acid Catalysts ◽  
Acid Catalysts ◽  
Alumina Catalyst ◽  
Reaction Conditions ◽  
Solvent Free Conditions ◽  
Wide Range ◽  
Silica Alumina

The synthesis of thioethers starting from alcohols and thiols in the presence of amorphous solid acid catalysts is reported. A silica alumina catalyst with a very low content in alumina gave excellent results in terms of both activity and selectivity also under solvent-free conditions. The reaction rate follows the electron density of the carbinol atom in the substrate alcohol and yields up to 99% and can be obtained for a wide range of substrates under mild reaction conditions.

scholarly journals Reaction Rate Retardation as a Method for Serum Alkaline Phosphatase Isoenzyme Measurement

1980 ◽  
Vol 17 (4) ◽  
pp. 192-198 ◽  
Author(s):  
Pamela B Brown ◽  
K O Lewis
Keyword(s):  
Alkaline Phosphatase ◽  
Reaction Rate ◽  
Serum Alkaline Phosphatase ◽  
Enzyme Reaction ◽  
Intestinal Alkaline Phosphatase ◽  
Wide Range ◽  
Alkaline Phosphatase Isoenzymes ◽  
Sensitivity And Selectivity ◽  
Rate Retardation ◽  
Alkaline Phosphatase Isoenzyme

A method for serum alkaline phosphatase isoenzymes using an enzyme reaction rate analyser is described. The complete urea-induced degradation of enzyme activity is monitored, from which individual isoenzyme activities are obtained by calculating the constituent exponential components of the degradation curve. Activities have been measured with adequate sensitivity and selectivity for up to four isoenzyme components in normal and in pathological sera. The identity of each isoenzyme present is assigned from its characteristic degradation half-life, and by this method bone and liver alkaline phosphatase are clearly distinguished and quantitated, and a composite value for placental-intestinal alkaline phosphatase activity is obtained. The approach promises to be applicable to a wide range of isoenzymes, and in analogy with ‘reaction rate’ the term ‘reaction rate retardation’ is suggested for the procedure.

Investigation of Factors Influencing the Formation of Tungstate-Based Inorganic-Organic Hybrid Nanobelts/Nanotubes

2007 ◽  
Vol 352 ◽  
pp. 85-88 ◽  
Author(s):  
De Liang Chen ◽  
Yoshiyuki Sugahara
Keyword(s):  
Reaction Rate ◽  
Molar Ratio ◽  
Long Range Order ◽  
Interlayer Water ◽  
Organic Hybrid ◽  
Lamellar Structures ◽  
Factors Influencing ◽  
Wide Range ◽  
Formation Behavior ◽  
Apparent Diameter

Tungstate-based inorganic−organic hybrid nanobelts/nanotubes were synthesized in a system of H2W2O7·xH2O/n-octylamine/heptane (n-octylamine:H2W2O7·xH2O molar ratio: 30), and the effects of the volume ratios of heptane to n-octylamine and the amounts of interlayer water in H2W2O7·xH2O on the formation behavior of the hybrids were investigated. The belt/tubelike hybrids obtained were 10–20 +m in length and 200–500 nm in apparent diameter. Large volume ratios of heptane to n-octylamine not only enhanced the degree of the long-range order of the lamellar structures in the hybrids, but they also improved the morphologic uniformity of the hybrids. The existence of interlayer water in H2W2O7·xH2O was indispensable to the formation of tungstate-based inorganic−organic hybrid nanobelts/nanotubes. The amounts of interlayer water in H2W2O7·xH2O varied over a wide range (x, from 0.85 to 4.1), had a neglectable effect on the morphology of the tungstate-based nanophase hybrids, but exerted a remarkable influence on the rate of the reaction of H2W2O7·xH2O with n-octylamine in the heptane solvent. The larger the amount of interlayer water, the more rapid the reaction rate.

scholarly journals Kinetic and Mechanistic Study of Rhodamine B Degradation by H2O2 and Cu/Al2O3/g-C3N4 Composite

Catalysts ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 317 ◽  
Author(s):  
Chunsun Zhou ◽  
Zhongda Liu ◽  
Lijuan Fang ◽  
Yulian Guo ◽  
Yanpeng Feng ◽  
...  
Keyword(s):  
Rate Constant ◽  
Rhodamine B ◽  
Active Sites ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Mechanistic Study ◽  
Al2o3 Composite ◽  
Degradation Rates ◽  
Wide Range ◽  
Alkaline Conditions

The classic Fenton reaction, which is driven by iron species, has been widely explored for pollutant degradation, but is strictly limited to acidic conditions. In this work, a copper-based Fenton-like catalyst Cu/Al2O3/g-C3N4 was proposed that achieves high degradation efficiencies for Rhodamine B (Rh B) in a wide range of pH 4.9–11.0. The Cu/Al2O3 composite was first prepared via a hydrothermal method followed by a calcination process. The obtained Cu/Al2O3 composite was subsequently stabilized on graphitic carbon nitride (g-C3N4) by the formation of C−O−Cu bonds. The obtained composites were characterized through FT-IR, XRD, TEM, XPS, and N2 adsorption/desorption isotherms, and the immobilized Cu+ was proven to be active sites. The effects of Cu content, g-C3N4 content, H2O2 concentration, and pH on Rh B degradation were systematically investigated. The effect of the catalyst dose was confirmed with a specific reaction rate constant of (5.9 ± 0.07) × 10−9 m·s−1 and the activation energy was calculated to be 71.0 kJ/mol. In 100 min 96.4% of Rh B (initial concentration 20 mg/L, unadjusted pH (4.9)) was removed in the presence of 1 g/L of catalyst and 10 mM of H2O2 at 25 °C, with an observed reaction rate constant of 6.47 × 10−4 s−1. High degradation rates are achieved at neutral and alkaline conditions and a low copper leaching (0.55 mg/L) was observed even after four reaction cycles. Hydroxyl radical (HO·) was identified as the reactive oxygen species by using isopropanol as a radical scavenger and by ESR analysis. HPLC-MS revealed that the degradation of Rh B on Cu/Al2O3/CN composite involves N-de-ethylation, hydroxylation, de-carboxylation, chromophore cleavage, ring opening, and the mineralization process. Based on the results above, a tentative mechanism for the catalytic performance of the Cu/Al2O3/g-C3N4 composite was proposed. In summary, the characteristics of high degradation rate constants, low ion leaching, and the excellent applicability in neutral and alkaline conditions prove the Cu/Al2O3/g-C3N4 composite to be a superior Fenton-like catalyst compared to many conventional ones.

Practical Deoxygenation of Oxazole N-Oxides by PCl3/Collidine

Synthesis ◽  
2018 ◽  
Vol 51 (02) ◽  
pp. 414-420
Author(s):  
Valerii Shirinian ◽  
Ilya Lonshakov ◽  
Alexey Zakharov ◽  
Andrey Lvov ◽  
Mikhail Krayushkin
Keyword(s):  
Functional Groups ◽  
Heterocyclic Compounds ◽  
Phosphorus Trichloride ◽  
Double Bonds ◽  
Wide Range

A new chemoselective method for the synthesis of 2-aryl-1,3-oxazoles by deoxygenation of the corresponding N-oxides has been developed. As the deoxygenation reagent, a previously unknown complex of collidine with phosphorus trichloride in a 2:1 ratio has been used. The developed method enabled the preparation of a wide range of 2-aryl-1,3-oxazoles comprising various functional groups in good yields. The advantage of this reagent is its tolerance to nitro, methyl, hydroxyl, formyl, and acetyl groups, and double bonds. Due to chemoselectivity and availability of reagents, the method may be used for deoxygenation of N-oxides of other heterocyclic compounds (thiazole, pyridine, quinoline, etc.).

Mechanism of Rubber Vulcanization with Sulfur

1938 ◽  
Vol 11 (1) ◽  
pp. 107-130
Author(s):  
W. K. Lewis ◽  
Lombard Squires ◽  
Robert D. Nutting
Keyword(s):  
Natural Rubber ◽  
Temperature Coefficient ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Reaction Rate ◽  
Complex Behavior ◽  
Double Bonds ◽  
Irreversible Reaction ◽  
Sulfur Addition

Abstract THAT vulcanization of rubber with sulfur always involves a chemical reaction consisting in the addition of sulfur to the double bonds of the rubber molecule has been conclusively established (18, 28). The facts indicate that this addition of sulfur to rubber is an irreversible reaction (31). The temperature coefficient of the reaction is high, increasing about 2.65 fold per 10° C. at ordinary curing temperatures (31). Furthermore, the reaction is apparently exothermic (4, 24). It is noteworthy that catalysts are apparently necessary, since synthetic rubbers prepared from pure materials add sulfur slowly, if at all. The proteins and perhaps the resins in natural rubber undoubtedly serve as accelerators. The curves for combined sulfur vs. time of cure for typical mixes are shown in Figures 1 and 2. Figure 1 is taken from the data of Kratz and Flower (16); the composition and temperature of cure for this mix are shown in Cranor's Table I (9). Figure 2, curve 1, is from Table I of Eaton and Day (10), and curve 2 from data obtained in this laboratory (27, Table I). Superficial inspection of these curves shows extraordinary divergence of type. Figure 1 is a typical fadeaway curve, characteristic of most chemical reactions, where the reaction rate decreases with decreasing concentration of the reacting materials. Curve 1, Figure 2, is an entirely different type, where the rate of sulfur addition is constant until nearly 70 per cent of the initial sulfur has reacted. Curve 2, Figure 2, shows even more complex behavior. Again the rate is constant in the initial portions of the cure. However, following this period, the rate increases markedly but later falls off, approaching zero, to give an S-shaped eurve.

Modeling of Gas Turbine Combustors—A Convenient Reaction Rate Equation

1972 ◽  
Vol 94 (3) ◽  
pp. 173-180 ◽  
Author(s):  
D. Kretschmer ◽  
J. Odgers
Keyword(s):  
Rate Equation ◽  
Reaction Rate ◽  
Reaction Order ◽  
Bimolecular Reaction ◽  
Rate Equations ◽  
Combustion System ◽  
Wide Range ◽  
Simple Mass ◽  
Rich Mixtures ◽  
Reaction Rate Equation

In order to model a practical combustion system successfully, it is necessary to develop one or more reaction rate equations which will describe performance over a wide range of conditions. The equations should be kept as simple as possible and commensurate with the accuracy needed. In this paper a bimolecular reaction is assumed, based upon a simple mass balance. Temperatures derived from the latter are related to measured practical ones such that, if required, an evaluation of the partly burned product composition can be made. A convenient reaction rate equation is given which describes a wide range of blow-out data for spherical reactors at weak mixture conditions. NVP2φ={1.29×1010(m+1)[5(1−yε)]φ[φ−yε]φe−C/(Ti+εΔT)}/{0.082062φyε[5(m+1)+φ+yε]2φ[Ti+εΔT]2φ−0.5} Analysis of the components used in the above equation (especially the variation of activation energy) clearly shows its empirical nature but does not detract from its engineering value. Rich mixtures are considered also, but lack of data precludes a reliable analysis. One of the major results obtained is the variation of the reaction order (n) with equivalence ratio (φ): weak mixtures, n = 2φ; rich mixtures, n = 2/φ. Some support for this variation has been noticed in published literature of other workers.

scholarly journals The Role Of Chemical Reaction In Waste-Form Performance

1987 ◽  
Vol 112 ◽  
Author(s):  
P. L. Chambré ◽  
C. H. Kang ◽  
W. W.-L. Lee ◽  
T. H. Pigford
Keyword(s):  
Mass Transfer ◽  
Steady State ◽  
Dissolution Rate ◽  
Chemical Reaction ◽  
Borosilicate Glass ◽  
Reaction Rate ◽  
Waste Form ◽  
Spent Fuel ◽  
Wide Range ◽  
Chemical Reaction Rate

AbstractThe dissolution rate of waste solids in a geologic repository is a complex function of waste form geometry, chemical reaction rate, exterior flow field, and chemical environment. We present here an analysis to determine the steady-state mass transfer rate, over the entire range of flow conditions relevant to geologic disposal of nuclear waste. The equations for steady-state mass transfer with a chemical-reaction-rate boundary condition are solved by three different mathematical techniques which supplement each other. This theory is illustrated with laboratory leach data for borosilicate-glass and a spherical spent-fuel waste form under typical repository conditions. For borosilicate glass waste in the temperature range of 57°C to 250°C, dissolution rate in a repository is determined for a wide range of chemical reaction rates and for Peclet numbers from zero to well over 100, far beyond any Peclet values expected in a repository. Spent-fuel dissolution in a repository is also investigated, based on the limited leach data now available.

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