Selectivity range

For some purposes it is desirable to have a sharp colour change over a narrow and selected range of pH this is not easily seen with an ordinary acid-base indicator, since the colour change extends over two units of pH. The required result may, however, be achieved by the use of a suitable mixture of indicators these are generally selected so that their pK ln values are close together and the overlapping colours are complementary at an intermediate pH value. A few examples will be given in some detail. 

High purity (here meaning a selected range of homologs, a low content of impurities, and a constant overall composition)... 

Acetoxypyran-2-one (169) reacted with chiral enolethers 170 under high pressure conditions. Diastereofacial selectivities ranged from 52/48 to 88/12 depending on the nature of the dienophile [63] (Equation 5.20). 

Stack) a selected range of columns is automatically mapped into a stack of histograms on common x- and y-scales the vertical offset between histograms corresponds to the largest frequency found in all bins. 

Since amines react more readily than alcohols in noncatalyzed reactions with anhydrides, the reaction is more difficult and initially required stoichiometric catalyst loadings [107], but could be performed in a catalytic sense with an O-acylated azlactone as acylating agent, which does not react with a benzylic amine at —50°C, but is capable of acylating the catalyst [108, 109]. Depending on the buUdness of the substrate, selectivities ranged from S = 11 to 27 (s = [ enantiomer l]/[ enantiomer 2])-... 

OS 30] ]R 30] [P 22] The synthesis of nine C-C bonded products was made from four carbamates and five silyl enol ethers [66, 67]. Conversions ranged from 49 to 69% the corresponding selectivities ranged from 67 to 100%. Similar performance was achieved when serially processing the same reactions (see Serial combinatorial synthesis). 

GL 1] [R 4] [P 2] Conversions from 17 to 95% were achieved using methanol as solvent (1.0-10.0 fluorine-to-toluene equivalents 0.1 M toluene room temperature 10 ml min gas flow 100 pi min methanol) [14]. The respective selectivities ranged from 37 to 10%. Taking into account also the difluorotoluenes and trifluorotoluenes gives a selectivity of about 45%. The yields passed through a maximum at 18%. 

The sorbents used for SPE are available in three basic formats, namely disks, prepacked cartridges, and syringe barrels, each with certain advantages. Solid media employed in SPE may be classified as nonpolar, polar and ion-exchange phases with mixed retention mechanisms (Table 3.41). The large sorbent selection ranges also... 

The American journal Chemical Marketing Reporter, CMR (2004), publishes a weekly review of prices for most chemicals. The prices for a limited number of chemicals in Europe can be found in European Chemical News, ECN (2004). U.S. prices, converted to the local currency at the current rate of exchange, can be used as a guide to the probable price in other countries. An indication of the prices of a selected range of chemicals is given in Table 6.4 (see p. 263). 

Selected range is from 55.00 to 105.00 Mean value in simulation was 72.48... 

Typical performance characteristics that should be considered in the validation are precision, accuracy, limit of detection, limit of quantitation, selectivity, range, linearity, robustness, ruggedness... 

P.G. Boswell and P. Buhlmann, Fluorous bulk membranes for potentiometric sensors with wide selectivity ranges observation of exceptionally strong ion pair formation. J. Am. Chem. Soc. 127, 8958—8959 (2005). 

The limit of quantitation (LOQ) may be set as the lowest standard in the selected range or as 0.4 times the lowest standard in the selected range, but must be greater than three times the mean value for the back-calculated value of the two zero standards. 

If the LOQ is 0.4 times the lowest standard in the selected range, samples with back-calculated values between the LOQ and the lowest standard in the selected range may be reported as their calculated value provided the S/N for the analyte is at least three. 

Samples with back-calculated values between 1.0 and 2.0 times the highest standard in the selected range are reportable by extending the calibration line up to 2 times the high standard. 

Prochiral cyclobutanones with a single substituent at the 3 position proved to be poor substrates for this catalyst (132). Selectivities ranging from 26-47% ee are obtained, Eq. 112. The authors postulate that initial attack of the peracid on the car-... 

In a comprehensive screen of the effect of TADDOL and BINOL-derived phosphites on the conjugate addition of diethylzinc to representative enones, Al-exakis et al. (181) revealed that the Feringa ligand exhibits the broadest scope, providing the conjugate adducts in selectivities ranging from 66 to 92% ee, Eq. 144. 

The addition to both benzaldehyde and 3-methylbutanal was tested. This approach proved generally successful with a number of ligands giving selectivities ranging from 94 to 80% enantiomeric excess (ee). 

Full scan experiments set the mass spectrometer in a cycle of repeatedly scanning a selected range of m/z values. The experiment is done primarily for structure elucidation, and the richness of structural... 

Designed to Calculate Energy Levels in Selected Range and Application to a (One-Dimensional) Morse Oscillator and (Three-Dimensional) HCN/HNC. 

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