Isomerism effects

This saturation of a double bond is analogous to the isomerism effected in the steroid aglycons, for when the latter are treated with alkali the system LXXXVII is transformed into LXXXVIII.46... 

The van der Waals volume can be related to the hydrophobicity of the solutes, and retention of molecular compounds can be predicted from their van der Waals volumes, 7r-energy, and hydrogen-bonding energy effects [72-74], It should be noted that the isomeric effect of substituents cannot be predicted with good precision because this is not simply related to Hammett s a or Taft s other hand, the hydrophobicity is related to enthalpy [75], Retention times of non-ionizable compounds were measured in 70 and 80% acetonitrile/water mixtures on an octadecyl-bonded silica gel at 25-60°C and the enthalpy values obtained from these measurements. 

The isomeric effect of the AAH value of substituted chlorobenzenes was very small. This means that the molecular size of the isomers is almost the same however, the actual size is not the same under these chromatographic conditions.38... 

The superiority of catalytic hydrogenation over reduction with sodium or aluminum amalgam as a means of converting hexoses to hexitols is apparent. The yields approach or reach the theoretical and the isomerizing effect of the alkaline reducing agent is avoided. Electrolytic reduction is not suitable as a laboratory method. 

Isomerization of cis- to trans,vic-Raney nickel at 60-90° (equations I and II). 

Meletov KP, Assimopoulos S, Tsilika I, Bashkin IO, Kulakov VI, Khasanov SS, Kourouklis GA (2001) Isotopic and isomeric effects in high-pressure hydrogenated fullerenes studied by Raman spectroscopy. Chem Phys 263 379-388... 

Oudejans, L. and Miller, R. E., State-to-state photodissociation of oriented HF HCl complexes Isotopic and isomeric effects, J. Phys. Chem. 99, 13670-13679 (1995). 

Isomeric effect—The additivity rule for bond energies applies only to compounds in a homologous series and small changes in structure cause deviations in the heats of formation. If the additivity rule were correct, saturated hydrocarbons possessing the same number of carbon and hydrogen atoms would have identical heats of formation. This, however, is not correct as is shown in Table CIX, where the experimental data indicate that the heat of formation... 

The spatial requirements produce an isomeric effect e.g., the ortho isomer is distinguished from the meta or para, cis is distinguished from trans, and diequatorial or equatorial axial positions are favored over diaxial. Furthermore, it is likely that most intramolecular H bonds deviate from the optimum linear configuration described earlier (Section 3.3.6), Absence of association, the second factor, means that intramolecular H bond formation does not produce deviations from normal behavior. 

Studies on the isomerizing effects of phosphates have extended to the catalyst Li3P04. The experimental results lead to the conclusion that this is a general method for the preparation of unsaturated alcohols from oxiranes. 

Relatively little is known about applications of this class of enzymes. In general, they catalyze geometric or structural changes within one molecule. According to the type of isomerization effected, they may be called racemases, epimerases, (cis-trans) isomerases, and tautomerases. Currently, about 126 isomerases are known, of which only about six are available commercially. 

The present results constitute a step forward in our understanding of the microscopic details that may lead to disparate behaviour in macroscopic glassy properties such as the fragility and also come into line with results given in Ref. 22 on a study of the isomeric effect concerning another glassy material. 

The isomer trends of the models were very useful for helping the identification of isomers. Cell cultures of human leukemia cell lines (THP-1) were incubated in the absence and presence of thiol compounds, ensuring that no trans compounds could come from the medium [45]. In parallel experiments, some millimolar levels of thiol compounds were added to the cell cultures during incubation, and the comparison of isomeric trends was carried out. A basic content of trans lipids in THP-1 cell membranes could be found during their growth without thiol, and after the addition of the amphiphilic 2-mercaptoethanol, it increased to 5.6% of the main fatty acid residues. Moreover, when a radical stress by y-irradiation is artificially produced in the cell cultures added with thiol, a larger isomerization effect could be seen, with trans lipid formation up to 15.5% in membrane phospholipids. The fatty acid residues most involved in this transformation were arachidonate moieties, as expected. 

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