Decomposition reaction rate

The temperature rate factor can be used to decrease the decomposition reaction rate by storing the hydrogen peroxide in a refrigerator. 

It was alluded to earlier that decomposition reaction rate and mechanism were affected by the presence of other substances. The chemical reactions between explosives and other substances are called chemical incompatibilities. These are very important in explosive systems that must be stored for long periods of time. Compatibility studies are directed not only to address the problem of degradation of explosives by other materials in a system, but also to address the degradation of other parts of a system caused by the explosive. Examples of the latter are (1) a case where a substance in the explosive compound caused severe corrosion of the metal bridge wire in a hot wire initiator, and (2) where NO2 vapors given off by the slow decomposition of an explosive in one part of a weapon system caused severe corrosion and subsequent failure of a printed circuit in another area of the weapon. 

Self-Accelerating Decomposition Temperature The minimum temperature that a mass of material, capable of an exothermic decomposition reaction, must be held such that the heat of decomposition exceeds the amount of energy lost to the surroundings. This will result in an increase in the mass temperature and acceleration of the decomposition reaction rate. 

In accordance with this scheme the ratio of the decomposition reaction rates of the radical C6Hn entering into the Voevodsky reaction can be expressed through the concentration of the product in the cracking gases in the following way ... 

Figure 2. Dependence of the naphtha cracking decomposition reaction rate constant on temperature (a) dependence of the naphtha cracking overall kinetic order on conversion (b)...

Table 6.2 Rate Constants (at Temperature Given) and Activation Energies for Some Initiator Decomposition Reactions...

Thus, for a successful fluorination process involving elemental fluorine, the number of coUisions must be drasticaUy reduced in the initial stages the rate of fluorination must be slow enough to aUow relaxation processes to occur and a heat sink must be provided to remove the reaction heat. Most direct fluorination reactions with organic compounds are performed at or near room temperature unless reaction rates are so fast that excessive fragmentation, charring, or decomposition occurs and a much lower temperature is desirable. 

Solvent polarity also affects the rate of peroxide decomposition. Most peroxides decompose faster in more polar or polari2able solvents. This is tme even if the peroxide is not generally susceptible to higher order decomposition reactions. This phenomenon is illustrated by various half-life data for tert-huty peroxypivalate [927-07-1]. The 10-h half-life temperature for tert-huty peroxypivalate varies from 62°C in decane (nonpolar) to 55°C in ben2ene (polari2able) and 53°C in methanol (polar). 

Dioxetanones decompose near or below room temperature to aldehydes or ketones (56). The decomposition reactions are weakly chemiluminescent Qc ca 10 ein/mol) because the products are poorly fluorescent. However, addition of 10 M mbrene provides 2iQc ca 10 ein/mol, and 2iQc on the order of was calculated at mbrene concentrations above 10 M after correcting for yield loss factors (57). The decomposition rates are first order ia... 

Therefore, first-order, decomposition rates for alkyl hydroperoxides, ie, from oxygen—oxygen bond homolysis, are vaUd only if induced decomposition reactions... 

Cracking temperatures are somewhat less than those observed with thermal pyrolysis. Most of these catalysts affect the initiation of pyrolysis reactions and increase the overall reaction rate of feed decomposition (85). AppHcabiUty of this process to ethane cracking is questionable since equiUbrium of ethane to ethylene and hydrogen is not altered by a catalyst, and hence selectivity to olefins at lower catalyst temperatures may be inferior to that of conventional thermal cracking. SuitabiUty of this process for heavy feeds like condensates and gas oils has yet to be demonstrated. 

If the decomposition reaction follows the general rate law, the activation energy, heat of decomposition, rate constant and half-life for any given temperature can be obtained on a few milligrams using the ASTM method. Hazard indicators include heats of decomposition in excess of 0.3 kcal/g, short half-lives, low activation energies and low exotherm onset temperatures, especially if heat of decomposition is considerable. 

The collision theory considers the rate to be governed by the number of energetic collisions between the reactants. The transition state theory considers the reaction rate to be governed by the rate of the decomposition of intermediate. Tlie formation rate of tlie intermediate is assumed to be rapid because it is present in equilibrium concentrations. 

A gas decomposition reaction with stoichiometry 2A —> 2B -i- C follows a second order rate law rj(mol / m s) = kC, where C is the reactant concentration in mol/m. The rate constant k varies with the reaction temperature according to the Arrhenius law ... 

When potassium fluoride is combined with a variety of quaternary ammonium salts its reaction rate is accelerated and the overall yields of a vanety of halogen displacements are improved [57, p 112ff. Variables like catalyst type and moisture content of the alkali metal fluoride need to be optimized. In addition, the maximum yield is a function of two parallel reactions direct fluorination and catalyst decomposition due to its low thermal stability in the presence of fluoride ion [5,8, 59, 60] One example is trimethylsilyl fluoride, which can be prepared from the chloride by using either 18-crown-6 (Procedure 3, p 192) or Aliquot 336 in wet chlorobenzene, as illustrated in equation 35 [61],... 

A collection of pH-rate profiles for drug decomposition reactions has been published. ... 

The differenee in reaction rates of the amino alcohols to isobutyraldehyde and the secondary amine in strong acidic solutions is determined by the reactivity as well as the concentration of the intermediate zwitterions [Fig. 2, Eq. (10)]. Since several of the equilibrium constants of the foregoing reactions are unknown, an estimate of the relative concentrations of these dipolar species is difficult. As far as the reactivity is concerned, the rate of decomposition is expected to be higher, according as the basicity of the secondary amines is lower, since the necessary driving force to expel the amine will increase with increasing basicity of the secondary amine. The kinetics and mechanism of the hydrolysis of enamines demonstrate that not only resonance in the starting material is an important factor [e.g., if... 

The most reliable method of preparing benzofuroxans is by decomposition of o-nitrophenyl azides. Decomposition can be achieved by irradiation, or more usually by pyrolysis temperatures between 100° and 1.50° are commonly used. Refluxing in glacial acetic acid is the recommended procedure for 4- or 5-sub-stituted 2-nitrophenyl azides, but with 3- or 6-substituted compounds higher boiling solvents are usually necessary. Quantitative studies on the reaction rate have been made, and a cyclic transition state invoked, an argument which has been used to account for the greater difficulty of decomposition of the 6-substituted 2-nitrophenyl azides. Substituent effects on the reaction rate have also been correlated with Hammett a constants, ... 

Umsetzung, /. transposition double decomposition conversion, change transformation reversal reaction transplantation exchange, sale, business. Umsetzungsgeschwindigkeit, /. velocity of transformation, reaction rate. 

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