Optimum reaction conditions

Note The chromatogram zones exhibit a broad spectrum of colors [3, 12] that is very dependent on the duration and temperature of heating. Therefore the optimum reaction conditions must be determined empirically. With a few exceptions (ferulic, 4-amino-benzoic and cumarinic acids) aromatic carboxylic acids do not react [3]. The reagent in 80 ethanolic sulfuric acid is reported to be most sensitive for steroids [25]. 

The kinetics of the reactions taking place when contacting flue gas t ntaining NO and O2 with aqueous Fe (EDTA) solutior were detennined. With this information, a steady state, rate based BiodeNOx absorber model was developed for a counter current packed colunm djsorber unit. The model has been tqipli to determine the optimum reaction conditions for the absorber. Absorber perfiirmance is improved considerably when operating at the low end of the tempaature range. 

Gay, R. J. McComb, R. B. and Bowers, G. N. Optimum reaction conditions for human lactate dehydrogenase isoenzymes as they affect total lactate dehyrogenase activity. Clin. Chem. (1968), U, 740-753. 

Real-time photoelectron-spectroscopic analysis of the band intensities revealed that the optimum reaction conditions required a temperature of 1100 K for the complete elimination of four molecules of N2. The formation of the valence isomer Ph—Si=N, which is predicted to be 400 kJ mol-1 less stable, can be excluded.53... 

Applying the slow and continuous monomer-addition (quasiliving) technique, we polymerized IBVE and MVE with the -DCC/ AgSbFg initiating system and defined optimum reaction conditions for the quasiliving polymerization of these monomers. Subsequent block polymerization starting poly(IBVE) quasiliving dications led to novel triblock polymers poly(aMeSt-b-IBVE-b-aMeSt) and poly-(MVE-b-IBVE-b-MVE). 

Reaction conditions transition metal = 1 mM, reaction time = 60 minutes at their optimum reaction condition. 

The enantioselective hydrogenation of prochiral substances bearing an activated group, such as an ester, an acid or an amide, is often an important step in the industrial synthesis of fine and pharmaceutical products. In addition to the hydrogenation of /5-ketoesters into optically pure products with Raney nickel modified by tartaric acid [117], the asymmetric reduction of a-ketoesters on heterogeneous platinum catalysts modified by cinchona alkaloids (cinchonidine and cinchonine) was reported for the first time by Orito and coworkers [118-121]. Asymmetric catalysis on solid surfaces remains a very important research area for a better mechanistic understanding of the interaction between the substrate, the modifier and the catalyst [122-125], although excellent results in terms of enantiomeric excesses (up to 97%) have been obtained in the reduction of ethyl pyruvate under optimum reaction conditions with these Pt/cinchona systems [126-128],... 

The effects of cosolvents on the reduced viscosity and yield are summarized in Table 9.5. DMAc and NMP lead to the formation of high-molecular-weight Bisphenol AF poly(formal) (7) in a high yield. The optimum reaction conditions are 48 mmol of DCM, 14 mmol of potassium hydroxide, and 5 ml of NMP for 5 mmol ofBisphenol AF, resulting in the formation ofBisphenol AF poly(formal) (7) with reduced viscosity of 4.62 dl/g in a 87% yield at 75°C.12... 

A series of attempts to discover optimum reaction conditions was made in view of preventing formation of by-products arising from the reaction of the acyl halogenide with different functional groups within the N-methyl glucamine molecule. Nonetheless, a subsequent purification step was necessary to remove by-products and unreacted starting material. This turned out to be complicated due to similar solubilities of both the... 

Alternative procedures for the generation of dichlorocarbene and dibromocarbene under phase-transfer catalysed conditions are also available. Where the reactive substrate is labile under basic conditions, the thermal decomposition of solid sodium trichloroacetate or bromoacetate under neutral conditions in an organic solvent is a valuable procedure [10-12], The decarboxylation is aided by the addition of a quaternary ammonium salt, which not only promotes dissolution of the trihaloacetate anion in the organic solvent, but also stabilizes the trihalomethyl anion. Under optimum reaction conditions, only a catalytic amount of the quaternary ammonium salt is required, as a large amount of the catalyst causes the rapid generation of the dichlorocarbene with resultant side reactions. 

After establishing optimum reaction conditions, the effect of chemical supplements upon epoxidase activity was re-examined. Several chemicals used in preliminary incubation mixtures and throughout optimizing experiments had no effect upon dieldrin production under optimum conditions. These are BSA, KC1 and NADH (Table V). Overall, there was a 22-fold enhancement of in vitro epoxidase activity when initial conditions (crude homogenate, Table IVJ are compared to optimum conditions (homogenate plus electron generator, Table V). FMN decreased, FAD slightly increased and PBO completely inhibited in vitro epoxidase activity (Table VI). 

These amounts may need to be altered if the reaction is not successful using these guidelines. The optimum reaction conditions may require different primer/template ratios and these can only be determined empirically... 

Figure 14. Time on stream dependence of (a) phenol conversion, and (b) orthoalkyl phenol selectivity on Cu0.5Co0.5Fe204 at optimum reaction conditions, described earlier. Different alkylation is indicated by the name of the alkylation agent in the left panel. 2,6-xylenol selectivity is given for methylation with MeOH/DMC.

Optimum reaction conditions were achieved with the bromomagnesium cuprate, and explored in several examples. 

The chiral dialuminum Lewis acid 14, which is effective as an asymmetric Diels-Alder catalyst, has been prepared from DIBAH and BINOL derivatives (Scheme 12.12). " The catalytic activity of 14 is significantly greater than that of monoaluminum reagents. The catalyst achieves high reactivity and selectivity by an intramolecular interaction of two aluminum Lewis acids. Similarly, the chiral trialuminum Lewis acid 15 is quantitatively formed from optically pure 3-(2,4,6-triisopropylphenyl)binaphthol (2 equiv) and MeaAl (3 equiv) in CH2CI2 at room temperature (Scheme 12.12). " The novel structure of 15 has been ascertained by NMR spectroscopic analysis and measurement of the methane gas evolved. Trinuclear aluminum catalyst 15 is effective for the Diels-Alder reaction of methacrolein with cyclopentadiene. Diels-Alder adducts have been obtained in 99% yield with 92% exo selectivity. Under optimum reaction conditions, the... 

The optimum reaction condition, in terms of operational simplicity and chemical yield, involves the use of the dinuclear rhodium catalyst tra s-[RhCl(CO)(dppp)]2 11... 

Optimum reaction conditions for the preparation of l-d-aldehydes from aryl, benzyl, and vinyl organometallics are under investigation by the submitters. 

Under optimum reaction conditions (See Table IV.), selectivity to linear dimer is controlled by the choice of temperature, solvent and tertiary phosphine. Toluene and tetrahydrofuran are the best solvents. Temperatures between 25 to 60 C with a triphenyl or tributylphosphine/palladium acetate catalyst give linear dimer selectivities in the 80 s. At 25 C in toluene, a palladium acetate/tributylphosphine catalyst gave 98.7% conversion and 89.6% linear, 4.7% branched, 1.9% cyclic, and 3.8% heavies selectivity. The linear dimerization reaction was second order in diene with a 3.6 Kcal/mole activation energy. 

The procedure has also been performed under microwave irradiation, and the optimum reaction conditions were found to be at a temperature of 160 °C for 10 min in an acetic acid, acetonitrile solvent mix <2004OL4775>. Product yields were of the order of 88-97% <2004OL4775>. 

In the electrogravimetry and coulometry described in Section 5.6, the substance under study is completely electrolyzed in obtaining the analytical information. A complete electrolysis is also carried out in electrolytic syntheses and separations. Electrolytic methods are advantageous in that they need no chemical reagent and in that optimum reaction conditions can easily be obtained by controlling electrode potentials. 

Several hundred restriction enzymes have been isolated and characterized. Nomenclature for the enzymes consists of a three-letter abbreviation representing the source (Eco — E. colt), a letter representing the strain (R), and a roman numeral designating the order of discovery. fcoRI is the first to be isolated from E. coli (strain R) and characterized. Table E15.1 lists several other restriction enzymes, their recognition sequence for cleavage, and optimum reaction conditions. 

C-H insertion a to oxygen would generate p-hydroxy or p-alkoxy esters. Thus, the reaction could be considered as a surrogate of the aldol reaction. In Vol. II, Chap. 16 of this series, the preliminary studies on C-H activation of tet-rahydrofuran were summarized [3]. Since then this reaction has been optimized such that the major C-H activation product 22a can be obtained in 97% ee [17]. The optimum reaction conditions (2 equivalents of THF in hexane at -50 °C) demonstrate the regioselectivity that is possible with this chemistry because no reaction with the solvent was observed under these mild conditions. 

The course of the reaction is strongly influenced by solvent effects. Thus, a detailed study of the optimum reaction conditions has been performed using five-membered ring substrates. According to these investigations CCI4 turned out to be the most suitable solvent63. 

We began our synthesis by finding the optimum reaction conditions for the catalytic asymmetric cyanosilylation of ketone 28 (Table 1). Based on previous studies,30 the titanium complex of a D-glucose derived ligand (catalyst 32 or 33) generally gives (/ )-ketone cyanohydrins, which is required for a synthesis of natural fostriecin. 

Secondly, the description of the general procedures given below, as distinct from the specific experimental procedures of the preparations described in earlier chapters, provides an excellent opportunity for the student to explore on the small scale the optimum reaction conditions, the chromatographic monitoring of the reaction, the methods of isolation and purification procedures (solvent extraction, recrystallisation, etc.) for the successful completion of the preparation. The small-scale nature of the experiments is of particular importance in providing experience of those techniques of reaction work-up in which mechanical loss is frequently the reason for failure. Such experience is vital to the synthetic chemist since many of the new chemo-, regio- and stereo-specific reagents are expensive and used in small-scale reactions. 

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