Reactant second-order

The reaction between ethylene bromide and potassium iodide in 99% methanol (inert) has been found to be first-order with respect to each reactant (second-order overall) (Dillon, 1932). The reaction can be represented by C2liiBr2 + 3K1 —> C2H4 + 2KBr + KI3 or A + 3B - products. 

First-order reactions have rates that depend on the concentration of one reactant. Second-order reactions have rates that depend on the concentrations of two reactants. 

Reactions in 1.83M Sulfuric Acid. In a medium of 1.83M sulfuric acid the reaction of or-Cr(OH2) 2(0204)2 with cerium(IV) was found to be of apparent second order, being first order in each reactant. Second-order rate plots based on spectro-photometric measurements at 25° are shown in Figure 2. The average of 11 kinetic runs which covered the reactant concentration ranges [Ce(IV)]o = 2.00 X 10-2 to 2.50 X 10-3Af and [cis-]0 = 1.00 X 10-2 to 2.50 X 10 W gave a mean value for the apparent second-order rate constant, k (= — [Ce(IV) / /[Ge(IV)][cis-]) of 1.06 ( 0.10) X 10-1 liter mole-1 sec.-1 The value in parenthesis refers to the standard deviation from the mean. 

Figure 13.22 Two-reactants, second-order reaction in CSTR-Separator-Recycle system...

Reactions like this one are followed by labeling one of the complexes with a radioactive isotopic tracer. In this case, water molecules in the reactant Ru complex might contain the isotope instead of the normal This reaction has been determined to be first order in the concentrations of both reactants (second order overall) and to have a rate constant (see Table 5.5) of about 44 iW s b On the other hand, the rate of water exchange in [Ru(H20)6] is considerably slower (with a rate constant between 10 and 10 s according to Figure 5.5). The rate of water exchange in [Ru(H20)g] would be still slower because of the -1-3 charge... 

Herein Pa and Pb are the micelle - water partition coefficients of A and B, respectively, defined as ratios of the concentrations in the micellar and aqueous phase [S] is the concentration of surfactant V. ai,s is fhe molar volume of the micellised surfactant and k and k , are the second-order rate constants for the reaction in the micellar pseudophase and in the aqueous phase, respectively. The appearance of the molar volume of the surfactant in this equation is somewhat alarming. It is difficult to identify the volume of the micellar pseudophase that can be regarded as the potential reaction volume. Moreover, the reactants are often not homogeneously distributed throughout the micelle and... 

The reaction of MeO /MeOH with 2-Cl-5(4)-X-thiazoles (122) follows a second-order kinetic law, first order with respect to each reactant (Scheme 62) (297, 301). A remark can be made about the reactivity of the dichloro derivatives it has been pointed out that for reactions with sodium methoxide, the sequence 5>2>4 was observed for monochlorothiazole compounds (302), For 2.5-dichlorothiazole, on the contrary, the experimental data show that the 2-methoxy dehalogenation is always favored. This fact has been related to the different activation due to a substituent effect, less important from position 2 to 5 than from... 

The rate of this reaction is observed to be directly proportional to the concentration of both methyl bromide and sodium hydroxide It is first order m each reactant or second order overall... 

The rate of a process is expressed by the derivative of a concentration (square brackets) with respect to time, d[ ]/dt. If the concentration of a reaction product is used, this quantity is positive if a reactant is used, it is negative and a minus sign must be included. Also, each derivative d[ ]/dt should be divided by the coefficient of that component in the chemical equation which describes the reaction so that a single rate is described, whichever component in the reaction is used to monitor it. A rate law describes the rate of a reaction as the product of a constant k, called the rate constant, and various concentrations, each raised to specific powers. The power of an individual concentration term in a rate law is called the order with respect to that component, and the sum of the exponents of all concentration terms gives the overall order of the reaction. Thus in the rate law Rate = k[X] [Y], the reaction is first order in X, second order in Y, and third order overall. 

The kinetics of hydrolysis reactions maybe first-order or second-order, depending on the reaction mechanism. However, second-order reactions may appear to be first-order, ie, pseudo-first-order, if one of the reactants is not consumed in the reaction, eg, OH , or if the concentration of active catalyst, eg, reduced transition metal, is a small fraction of the total catalyst concentration. 

Diels-Alder reactions with butadiene are generally thermally reversible and can proceed in both gas and Hquid phases. The reactions are exothermic and foUow second-order kinetics first-order with respect to each reactant. 

Dichlorine monoxide, which exists in very low equiUbrium concentrations in dilute HOCl solutions, is nevertheless a kineticaHy significant reactant. Eor example, although tetracyanonickelate(II) can be oxidized by chlorine in aqueous solution to /n j -Ni(III) (CN)4(H20)2 , the second-order rate constant at 25°C for oxidation with CI2O is 40 times greater than for CI2 and 2.6 x 10 greater than for HOCl (31). 

At high reactant concentrations, this intermediate is favored and rapidly formed. It then decomposes in a second order reaction to form chlorine dioxide and chlorine ... 

The esterification of -butyl alcohol and oleic acid with a phenol—formaldehydesulfonic acid resin (similar to amberHte IR-100) is essentially second order after an initial slow period (52). The velocity constant is directiy proportional to the surface area of the catalyst per unit weight of reactants. 

Tubular flow reaclors operate at nearly constant pressure. How the differential material balance is integrated for a number of second-order reactions will be explained. When n is the molal flow rate of reactant A the flow reactor equation is... 

A reartant A diffuses into a stagnant liquid film where the concentration of excess reactant B remains essentially constant at C q. At the inlet face the concentration is Making the material balance over a differential dz of the distance leads to the second-order diffusional equation,... 

Reactions involving collisions between two molecular species such as H2 and I2, or between two HI molecules are called bimolecular or second-order homogeneous reactions, because they involve the collision between two molecular species, and they are homogeneous since they occur in a single gas phase. The rates of these reactions are dependent on the product of the partial pressure of each reactant, as discussed above, and for the formation of HI, and the decomposition of HI,... 

The concerted displacement mechanism implies both kinetic and stereochemical consequences. The reaction will exhibit second-order kinetics, first-order in both reactant... 

TWo types of rate expressions have been found to describe the kinetics of most aromatic nitration reactions. With relatively unreactive substrates, second-order kinetics, first-order in the nitrating reagent and first-order in the aromatic, are observed. This second-order relationship corresponds to rate-limiting attack of the electrophile on the aromatic reactant. With more reactive aromatics, this step can be faster than formation of the active electrq)hile. When formation of the active electrophile is the rate-determining step, the concentration of the aromatic reactant no longer appears in the observed rate expression. Under these conditions, different aromatic substrates undergo nitration at the same rate, corresponding to the rate of formation of the active electrophile. 

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 ... 

Assume that the reaction between A and B is second order and is represented by A -i- B —> products where A is the limiting reactant. The rate expression is... 

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