Effects of isomerization

Table 29.7 Effect of isomerism of ring structure in linear polymers on melting point...

Example The effects of isomerization upon thermal stability of butyl ions, C4H9 are impressing. This carbenium ion can exist in four isomers with heats of formation that range from 837 kJ mol in case of -butyl over 828 kJ mol for wu-butyl (also primary) to 766 kJ mol for 5cc-butyl to 699 kJ mol in case of t-butyl, meaning an overall increase in thermodynamic stability of 138 kJ mol (Chap. 6.6.2) [36]. 

Rutkowski JV, Fermn VH Comparison of the teratogenic effects of isomeric forms of aminophenol in the Syrian Golden Hamster. Toxicol Appl Tharrmcol 63 264, 1982... 

Effects of Isomerism Geometrical isomers of coordination compounds can exhibit different values of redox potential, as accounted for, in various cases, by simple djr orbital level splitting diagrams or by MO calculations. The dependence of the relative stability and redox behavior of the geometrical isomers on the electronic configuration of the metal is also... 

Table 7. The effect of isomerism of diglycidyl ethers of bisphenols on the kinetic parameters of their interaction with 4,4 -diamino-3,3 -dichlorodiphenylmethane 1041...

JA Keverling Buisman, KH Hanewald, FJ Mulder, JR Roborgh, KJ Keuning. Evaluation of the effect of isomerization on the chemical and biological assay of vitamin D. J Pharm Sci 57 13 26-1329,1968. 

Prior to Takegami s studies, the effect of isomerization of acylcobalt carbonyls on the products of the reaction between cobalt hydrocarbonyl and olefins had received little attention. Terminal olefins had been found to give a mixture of linear and branched products at low temperatures under carbon monoxide, and this was taken as reflecting the mode of addition of cobalt hydrocarbonyl (62, 73, 147). In view of the slow rate of isomerization of acylcobalt carbonyls this seems justified. However, it is worth noting that branched products predominated in the reaction of 1-pentene with hydrocarbonyl under nitrogen even when the olefin had isomerized only to the extent of 50% (73). Both isobutylene and alkyl acrylates had been found to produce branched products. It was suggested that isobutylene, with an... 

Meot-Ner, M., and Speller, C. V., Filling of solvent shells about ions. 1. Thermochemical criteria and the effects of isomeric clusters, J. Phys. Chem. 90, 6616-6624 (1986). 

The purity of the prepared solutions can be checked by the criteria discussed above. For special surfactants, a specific analysis of impurities by very sensitive methods is possible. Czichocki et al. (1981) and Vollhardt Czichocki (1990) have shown the strong impurity effect of isomeric alcohols on the adsorption properties of sodium alkyl sulphates. The purity of the solutions could be analysed in this case by a highly sensitive HPLC method, which carmot simply be transferred to other surfactant systems. 

Describe the differential anticoagulant effects of isomeric warfarin. 

In subsequent work, the effects of isomeric fluoroprolines, either in the X- or Y-position of the X-Y-Gly motif, have been extensively studied by several groups. For example, Raines and coworkers determined that in contrast to 4R-FPro in the Y-position that enhances hehx stability, TS -FPro in the Y-position precludes triple helix formation. Furthermore, replacing Pro with 4/f-FPro in the X-position decreased helical stability of (4R-FPro-Pro-Gly)7 and (4R-FPro-Pro-Gly])io, whereas 45-FPro in the corresponding peptides increased stability. The hyperstability of the 45-FPro and 4/ -FPro-containing peptides was ascribed to stereoelectronic effects that preorganize main-chain dihedral angles to correspond to the conformation found in the triple helix. The effects were not additive because peptides having both 45-FPro in the X-position and 4/ -FPro in the Y-position did not form helices. ... 

Effects of isomerizations. Isomerization of any of the transitory complexes, including central complexes, has no effect on the above distribution equations. 

To understand the effects of isomerism on the infrared spectra of coordination compounds. 

E. Segre et al. Italy, USA Chemical effect of isomeric transition attributable... 

Hunter, J.E. (1992) Safety and health effects of isomeric fatty acids, in Fatty Acids in Foods and Their Health Implications, ed. C.K. Chow, Marcel Dekker, New York, pp. 857-868. 

The properties of PLA are significantly influenced by the stereochemistry of its monomers. When PLA has high stereochemical purity, it tends to form a highly crystalline structure. Copolymerization of different lactide isomers can yield a variety characteristics of PLA. The effect of isomerization in PLA can be detected by IR and NMR spectroscopic methods. Many studies have proven that PLA has a low solubility in a wide range of solvents/liquids, such as water, alcohol and paraffin. This indicates that PLA can be safely employed as a food packaging material without causing adverse health effects. In addition, PLA also possesses barrier properties that are just as effective as LDPE and PS. The green aspect of PLA means that it represents a viable environmentally friendly substitute for petrochemical-based polymers. 

Scheme 6 The effect of isomerization on the caiculated shift of the indole nitrogen of 59 and 60.

A Nakajima. Effects of isomeric solvents on vibronic band intensities in fluorescence spectrum of pyrene. J Mol Spectrosc 61 467, 1976. 

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