Yield determination

Sufficient dry ether (approximately 100 ml.) is added to bring the organomagnesium products into solution. Aliquot portions of the solution are then added to a known volume of standard hydrochloric acid, and the excess acid is determined by titration with standard base. Yields determined in this way tend to be a few percent higher than those determined by collection of w-butane (Note 12). 

Parallel reactions. Show how the three rate constants that characterize the hydrolysis of isopropyl bromide in alkaline solution, Eqs. (3-68)—(3-70), can be obtained from studies of the kinetics and yields determined over a range of [OH" j. 

Yields determined by gas chromatography (Note 20). Preparative scalo yields are usually approximately 10% lower. 

Yield determined by proton magnetic resonance spectroscopy. 

The structural abbreviation Ts is used for p-toluenesulfonate. Yield determined by gas chromatography. 

Figure 4.43. Yields determined for a large number of batches of four bulk chemicals and four drug substances. During the early synthesis steps the yields are variable 10 batches run during one campain of the first compound clump near 95%. The result at about 107% is due to analytical variability and/or calibration bias. The final synthesis step of a drug compound, for which the aggregate value of a kilogram of material is much higher, has been trimmed for maximal yield.

Acetone-Je solvent yields determined by H NMR and internal standard unless otherwise indicated. Isolated. Equilibrium ratio of 9 and 10, also reached from either side within 2-4 h using 2 mol% 2 at 70°C. Unreacted 11 (29%) and an unidentified isomer (10%) also present. 

The starting point is P = 10A and T = SOB and the yield is 50 lb/hr. A unit step will now made in one of the two directions and the yield determined. Assume the pressure is increased and the yield is 55 lb/hr. This move was a success since the desired response, an increase in the yield, was obtained. This is shown on Figure 14-3. Next the temperature is increased and another success occurs. 

Intersystem crossing quantum yields determined by the methods discussed in this section and other methods<24) are presented in Table 5.6. 

Figure 4. Dependence of tar yield, determined by low-temperature Gray-King carbonization assay, n atomic hydrogen-to-carbon ratio for a wide range of Australian coals. Tar yield = 50.4 X H/C — 25.9 correlation coefficient, 0.95.

Mozumder and Magee, 1967), the success of the geminate pair model in kinetics (Warman et al., 1969 Rzad et al, 1970) and in free-ion yield determination (Hummel and Allen, 1966 Freeman, 1963a, b) has been rationalized on the basis that in multi-ion pair spurs all but the final e-ion pair would quickly neutralize due to intense internal coulombic interaction. Therefore, emphasis is laid in this section on the geminate pair with two caveats ... 

Photochemical reactions of the pyrimidine polymers in solution were studied to determine the quantum yields of the intramolecular photodimerization of the pyrimidine units along the polymer chains. Photoreactions of the polymers were carried out in very dilute solutions to avoid an intermolecular(interchain) photodimerization. Quantum yields determined at 280 nm for the polymers (1-6 in Figure 1) are listed in Table I. The quantum yield of the 5-bromouracil polymer [poly(MAOU-5Br)] could not be determined because of side reactions of the base during the irradiation. 

Table 4.4 The effect of the internal heavy atom effect on the fluorescence efficiency of naphthalene and its derivatives. Fluorescence quantum yields determined in solid solution at 77K...

Fluorescence quantum yields determined in solid solu-... 

The cytotoxic and photocytotoxic effects of two water-soluble fullerene derivatives, a dendritic CL mono-adduct and the malonic acid CL tris-adduct were tested on Jurkat cells when irradiated with UVA or UVB light (Rancan et al., 2002). The cell death was mainly caused by membrane damage and it was UV dose-dependent. Tris-malonic acid fullerene was found to be more phototoxic than the dendritic derivative. This result is in contrast to the singlet oxygen quantum yields determined for the two compounds. 

Product yields determined by HPLC analysis. The values in parenthesis are theoretical product yields calculated as described in Ref. 42. 

Quantum yields determinations lead to analogous conclusions, although differences in the ortho-to-para ratio are found probably because of experimental reasons. However, the ortho selectivity seems to be well established. Phenyl acetate irradiated in water gives the following quantum yields of product formation 0.16 (ortho), 0.067 (para), and 0.048 (phenol) in the presence of an excess of (3-cyclodextrin, they change to 0.23 (ortho), 0.053 (para), and 0.27 (phenol) [260]. As can be seen, the ortho product is favored in the hydrophobic microenvironment of the cyclodextrin. Phenol quantum yield is enhanced with respect to the irradiation without cyclodextrin, which has been interpreted in terms of H abstraction from the inner walls of the host oligosaccharide. 

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