Equivalent reaction time

Electrophile Additive (equivalents) Reaction time External/Internal... 

Run Aryl-H Lewis Add Equivalents Reaction Time Yield (%) ct p... 

In the case of an isothermal mode of operation for a measurement and provided that the reference temperature is identical with the isothermal test temperature, this equivalent reaction time automatically becomes identical with the true reaction time. In the case of a none-isothermal mode of operation or the choice of a reference temperature which does not correspond to an isothermal test temperature, all thermal conversion data X(t) are plotted over h(t). In order to obtain the different h(t) data, a first estimation of the activation temperature has to be made. If the activation temperature was correctly chosen and if, at the same time, the process can be described with a single gross reaction equation with sufficient accuracy, then all the different data sets plotted over h(t) must take an identical course. The first estimate on the activation temperature can be obtained from the slope of the linearized functional relationship... 

Even if the above problems can be resolved, batch reactors can measure with accuracy the intrinsic rates of slow pyrolysis reactions. For faster reactions, the time required to heat the sample up to reaction temperature and then cool it down becomes an appreciable fraction of the total, and thus the accuracy with which data can be obtained becomes progressively poorer. If, however, the temperature history is well-defined, the non-isothermal data can be corrected using the "equivalent reaction time" concept (Hougen and Watson, 1947), which can provide, in some cases, a reasonable accuracy. The equivalent reaction time is the time required at a reference temperature to produce the same conversion as that obtained in the actual non-isothermal operation. 

The Equivalent reaction Time (ET) can be determined by knowing the appropriate first order kinetics of the n-hexadecane decomposition for corresponding reaction conversions at the end of the TRT period in actual runs. The ET has been evaluated to be equal to 25 ms, 18 ms and 12 ms for the three temperatures of 800, 900 and 1000°C, respectively. Therefore, the Effective Residence Time is ... 

Acetone in conjunction with benzene as a solvent is widely employed. With cyclohexanone as the hydrogen acceptor, coupled with toluene or xylene as solvent, the use of higher reaction temperatures is possible and consequently the reaction time is considerably reduced furthermore, the excess of cyclohexanone can be easily separated from the reaction product by steam distillation. At least 0 25 mol of alkoxide per mol of alcohol is used however, since an excess of alkoxide has no detrimental effect 1 to 3 mols of aluminium alkoxide is recommended, particularly as water, either present in the reagents or formed during secondary reactions, will remove an equivalent quantity of the reagent. In the oxidation of steroids 50-200 mols of acetone or 10-20 mols of cyclohexanone are generally employed. 

From the data in Fig. 4.8b, estimate the shift factors required to displace the data at 0 = 0.5 (consider only this point) so that all runs superimpose on the experiment conducted at 128 C at 0 = 0.5. Either a ruler or proportional dividers can be used to measure displacements. Criticize or defend the following proposition Whether a buffered aqueous solution of H2O2 and 1. containing small amounts of S2O3 and starch, appears blue or colorless depends on both the time and the temperature. This standard general chemistry experiment could be used to demonstrate the equivalency of time and temperature. The pertinent reactions for the iodine clock are... 

Carbonates ate manufactured by essentially the same method as chloroformates except that more alcohol is required in addition to longer reaction times and higher temperatures. The products are neutralized, washed, and distilled. Corrosion-resistant equipment similar to that described for the manufacture of chloroformates is requited. Diaryl carbonates are prepared from phosgene and two equivalents of the sodium phenolates or with phenols and various... 

Another difference between the data and the calculations shows up at extended reaction times. Freeman and Lewis show a maximum concentration of trimethy-lolphenol at about 50 h reaction time. After this point, the concentration falls dramatically. This is apparently due to formation of condensation products which reach noticeable, but low, levels at about 50-60 h. After the reaction has been allowed to proceed for 1000 h, the level of the condensation product reported is equivalent to that of trimethylolphenol, which has fallen to about one third of its maximum concentration. This accounts reasonably well for the loss in trihydroxymethyl phenol, since two moles are consumed to make one mole of dimer. As the calculation contains no information about the condensation reaction, it predicts that the level of trimethylolphenol plateaus at about 98% yield on phenol. 

As follows from Table I (see Section VII Index of Tables), the yields in 4-acetylenyl compounds depend both on the reaction time and on the structure of the aromatic and acyclic components (molecular polarity). If more than one equivalent of diazomethane is used, N-methylation of pyrazole occurs. 

Two procedures have been developed for the aminohydroxylation of a, 3-unsat-urated amides Procedure A for products that are insoluble in the reaction mixture and Procedure B for soluble products (Scheme 12.17) [48]. These differ only in that the former requires a 10-25% excess of chloramine-T and t-BuOH as the cosolvent, while the latter uses only one equivalent of the chloramine salt and MeCN as the cosolvent. The excess of chloramine-T in Procedure A allows better turnover near the end of the reaction, and the trace amount of p-toluenesulfonamide byproduct can be removed by recrystallization. However, elimination of the necessity to remove p-toluenesulfonamide far outweighed the inconvenience of slightly longer reaction times needed in procedure B without the use of excess chloramine salt. 

Linking the ketone and carboxylic acid components together in an Ugi reaction facilitates the synthesis of pyrrolidinones amenable to library design. The three-component condensation of levulinic acid 30, an amine and isocyanide proceeds under microwave irradiation to give lactams 31 [65]. The optimum conditions were established by a design of experiments approach, varying the equivalents of amine, concentration, imine pre-formation time, microwave reaction time and reaction temperature, yielding lactams 31 at 100 °C in poor to excellent yield, after only 30 min compared to 48 h under ambient conditions (Scheme 11). 

Alternatively, 3-phenyl pyrazinone was prepared via Suzuki reaction, when a polymer-bound pyrazinone was irradiated with 4 equiv of phenylboronic acid, 5 equiv of Na2C03 and 20 mol % of Pd[P(Ph)3]4 as the catalyst in DMF as the solvent (Scheme 36). Contrary to the results obtained in solution phase [29], all attempts to drive the reaction toward the formation of disub-stituted compound, using higher equivalents of reagents or longer reaction times, were unsuccessful. Apphcation of aqueous conditions afforded mixtures of 3-mono and 3,5-disubstituted pyrazinones. 

Observe that aok has units of reciprocal time so that aokt is dimensionless. The grouping OQkt is the dimensionless rate constant for a second-order reaction, just as kt is the dimensionless rate constant for a first-order reaction. Equivalently, they can be considered as dimensionless reaction times. For reaction rates governed by Equation (1.20),... 

Finally, reaction of primary, secondary, or tertiary alcohols 11 with Me3SiCl 14 in the presence of equivalent amounts of DMSO leads via 789 and 790 to the chloro compounds 791 [13]. n-Pentanol, benzyl alcohol, yS-phenylefhanol or tert-butanol are readily converted, after 10 min reaction time, into their chloro compounds, in 89-95% yield, yet cyclohexanol affords after reflux for 4 h cyclohexyl chloride 784 in only 6% yield [13] (Scheme 6.5). 1,4-Butanediol is cyclized to tetrahydrofuran (THF) [13a], whereas other primary alcohols are converted in 90-95% yield into formaldehyde acetals on heating with TCS 14 and DMSO in benzene [13b] (cf also the preparation of formaldehyde di(n-butyl)acetal 1280 in Section 8.2.1). 

A similar result is obtained with 30 equivalents of H2O added but a long reaction time is required namely 215 h. Nevertheless, in all cases a black precipitate of bulk Rh(0) is visible at the end of the reaction justifying the destabilization of nanoclusters due to the interaction of H or H2O with the basic P2Wi5Nb3062 polyoxoanion. Finally, the partial hydrogenation of anisole to yield 1-methoxycyclohexane (up to 8%) with a soluble nanocluster catalyst has been reported by Finke and coworkers (see Sect. 3). 

Catalytic hydrogenolysis of the bisbenzylated Boc-neonactin A (21 in Scheme 4.97) using 10% Pd/C provided an inseparable mixture of the deben-zylated product and the N4-deshydroxy compound (22).343 Various manipulations of the reaction conditions including changing the solvent, the mol equivalents of Pd, and the reaction time proved unsuccessful. But with the use of an extended period of reaction time, the N-O bond can be completely removed. The bisbenzylated Boc-neonactin A and 10% Pd/C in EtOH were stirred under a hydrogen atmosphere for 7 days, providing the N4-deshydroxy compound in 70% yield (Scheme 4.97). 

Figure 12.11 represents targeting in interval (0.25-0.51 kg salt/kg water). This interval, as shown in Fig. 12.8, has the B and the C reactions with an overall water demand of 560 kg. Since both these reactions start before the completion of the washing operation of product A, no reusable water is available in the reaction time subintervals. This implies that fresh water will have to be used. The accumulated fresh water demand is, therefore, 1560 kg. As this is the last concentration interval, this quantity presents itself as the target for the optimal design. This is equivalent to a 34% reduction in freshwater demand compared to the base case. 

In its reactions, 84 may serve as a source of 85. Treatment of 84 with the tetraazathiapentalene derivative 86 gave two products 87 and 88. Using 86 in a higher molar equivalent and application of a longer reaction time, thiadiazo-lopyrimidine derivative 88 was obtained in a higher yield (Equation 4) <2004JHC99>. 

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