Isomer effects

Maleic and fiimaric acids have physical properties that differ due to the cis and trans configurations about the double bond. Aqueous dissociation constants and solubiUties of the two acids show variations attributable to geometric isomer effects. X-ray diffraction results for maleic acid (16) reveal an intramolecular hydrogen bond that accounts for both the ease of removal of the first carboxyl proton and the smaller dissociation constant for maleic acid compared to fumaric acid. Maleic acid isomerizes to fumaric acid with a derived heat of isomerization of —22.7 kJ/mol (—5.43 kcal/mol) (10). The activation energy for the conversion of maleic to fumaric acid is 66.1 kJ/mol (15.8 kcal/mol) (24). 

Kritchevsky, D., Tepper, S.A., Wright, S., Tso, P., Czarnecki, S.K. 2004. Conjugated linoleic acid isomer effects in atherosclerosis Growth and regression of lesions. Lipids. 39, 611-616. 

Price, J. M. Kenttamaa, H. 1. Characterization of two chloro-substituted m-benzyne isomers effect of substitution on reaction efficiencies and products, 7 Phys. Chem. A 2003,107, 8985-8995. 

D. A. Isom, Effective temperature method development. The Applications Notebook, LC-GC February (2004), 60. 

The results for all of the intermediate isomers are compared with the experimental data in Table I. The agreement is excellent both for the intermediate isomer effects and for the CD4 isotope effects over a broad temperature range. A comparison is also given with the results that would be calculated for intermediate isomers if free surface rotation was assumed. It is concluded that hindered rotation is occurring on this surface. This is an important result. (A similar conclusion concerning the existence of hindered rotation in the liquid phase of methane recently has been drawn by Jeevanandam, Craig, and Bigeleisen (18) from an analysis of new and published vapor pressure data.) Note that the calculated effects are not particularly sensitive to the choice of B because for this particular system the A factor is by far the predominant term. This is even true for the... 

Mixtures of mandelic acid and talc were ball-milled and analyzed by IR spectroscopy to investigate the optical isomer effect on the mechanochemical interaction [43], The IR spectra showed that a complex was formed between talc and the hydroxyl group and the COOH group of mandelic acid. It was also found that the covalent character in the carboxyl group was greater for (RS)-mandelic acid than for the R-isomer and the S-isomer. 

INTRODUCTION A. Differences in potency and D. Isomer effects on excretion... 

E. Pfeiffer s rule A. Isomer effects on absorption E. Deletion of the chiral center... 

Huang X, Kong L, Li X, Zheng C, Zou H (2003) Molecular imprinting of nitrophe-nol and hydroxybenzoic acid isomers effect of molecular structure and acidity on imprinting. J Mol Recogn 16(6) 406—411... 

To calculate the isomer effect Atkinson et al. [67] used the Cvetanovic equation [68] ... 

IV Optical isomerism and pharmacokinetic effects A Isomer effects on absorption and... 

Isomer effects on metabolism Isomer effects on uptake Isomer effects on excretion Practical considerations A Racemates or enantiomers ... 

The geometrical isomers of the tris-complex with P-alanine were synthesized by Celap et al., since the method of Ley-Winkler failed. With the hexaamminecobalt-(III) complex the product was c-isomer with a small amount of mer-isomer. The reaction between sodium tricarbonatocobaltate(III) trihydrate and p-alanine in aqueous solution under heating yielded wer-isomer effectively. 

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