Comparison stability

N HCl, EtOH, reflux, 90% yield for cholesterol. Although a direct stability comparison was not made, this group should be more stable than the THP group for the same reasons that the anomeric ethers of carbohydrates are more stable than their 2-deoxy counterparts. 

Knoxville compared to Nashville. The stability comparisons are given in Table 21-4. The frequencies are very nearly the same, with only A and B stabilities being slightly greater at Knoxville at the expense of the D stability. Stability G is more stable than Pasquill s F. 

Stability Comparison hetween TBDMS, TIPS, and TBDPS Alkyl Ethers (10)... 

Effect of Chelate Ring Size on Complex Stability Comparison of Stabilities of Complexes of EDTA (Chelate Ring Size Five Involving the Two Nitrogens) and TMDTA (Analogous Chelate Ring Size Six ) ... 

This means that the sequestration equilibrium reaction will be pH-dependent. The constant K is known as the conditional equilibrium constant. However, for stability comparisons between complexes of the same denticity, it may be more convenient to compare the equilibrium constant for the proton independent reaction between iron and siderophore. This can also be useful in a theoretical sense, as it allows comparison of complex stability where siderophores have different protonation constants. However, this approach does not account for competition between H+ and Fe3+ for binding, which is always present in a real situation in aqueous solution. 

Stability comparisons between siderophore complexes with different binding stoichiometries are complicated by the fact that the units for the concentration equilibrium constants are different. Also, since the Fe3+ binding moieties have different pKa values competition for binding with H+ differs, which will not be reflected in the pH-independent / mlh values. Therefore, it is important to have a scale for iron-siderophore complex... 

We conclude that L2a-Qb donor-donor interactions are generally ineffective at lowering the total variational energy,28 whereas L2a-f2b donor-acceptor interactions are universally stabilizing. Comparison of Fig. 3.2 (or Fig. 1.3) with Fig. 3.13 shows clearly how this fundamental difference arises from the Pauli restriction on orbital occupancies. 

Influence of Sample Thickness and 02 Diffusion. As shown above, the overall conversion of thermal degradation can depend of the sample thickness in the diffusion-controlled regime. Thus, stability comparisons are only valid for samples of comparable thickness. Let us now compare two polymers of glass transition temperatures Tgl and Tg2, oxidized at a temperature T, such that Tgl < T < Tg2. Even if the intrinsic oxidation rates are equal, polymer 1 will appear more unstable than polymer 2 because oxygen diffusion is faster above than below Tg. The thickness of the oxidized layer will be higher for polymer 1 than for polymer 2. 

The firm thermodynamic status of log KR for reduction half-reactions permits the use of these parameters in the normal way (see Section 1.2 and Special Topic 1) to evaluate equilibrium activities of oxidized and reduced species and to compare the stabilities of reactants and products in redox reactions. As an example of a stability comparison, consider the possible reduction of N(V) to N(0) through the oxidation of C(0) to C(IV) in a soil solution.13 The reduction half-reaction for denitrification is implicit in Eq. 2.20 that for C oxidation is... 

To determine the relative effectiveness of polymeric phenolic phosphites as heat stabilizers, comparisons were made with several commonly used hindered phenolics. Formulations containing 0.4% DLTDP and 0.1% phenolic were prepared and tested for heat stability in a 300°F. forced-draft oven. Three 75-mil, 1-inch diameter discs were placed in the oven, and days to failure were noted as the time for two out of three discs to craze crumble. 

Colloidal Stability Comparison of Sedimentation with Sedimentation Flocculation... 

BH3, toluene converts the p-AOM ether into a methyl ether. For a stability comparison of this group with MTM, SEM, BOM and EOM to various hydride reagents see the section on SEM ethers. ... 

The factors that are generally important to know are the operational stability (also termed the useful lifetime) and the storage stability. Comparison of literature data on these properties is sometimes difficult because the experimental conditions employed to establish the biosensor stability vary widely. It appears most practical to use the sensor intermittently for analysis and... 

The stereochemistry of the toxisterols B Is Inferred from spectroscopic data and stability comparisons (Figure 24). In the methanol Irradiation mixtures, evidence (TLC, UV) has been... 

Fig. 5 Stability comparison of conformationscf n-receptors and their cation-n complexes. (View this art in color at www.dekker.com.)...

Stabilities determined in this way are dramatically dependent upon conditions. Buffer type, pH, and ionic strength can have major effects, as well as agents such as substrate, product, cofactors, and metal ions (especially calcium). Stability comparisons made between enzymes on this basis must be regarded as approximations only, and the conditions carefully defined. 

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