Factors involved in the high pressure liquid chromatographic separation of alkenes by means of argentation chromatography on ion exchangers: Overview of theory and new practical developments

Abstract

The literature on the use and theory of silver(I) complexation (argentation) chromatography is reviewed. Apolar isomeric alkenes, for example numerous terpenes and fatty acids, can be well resolved by means of high pressure liquid chromatography on cation exchange materials coated with silver(I) ions, but unfortunately the mechanism on which these separations are based is not fully understood. As part of an attempt to provide a predictive model for the separation of volatile alkenes, the retention of more than 40 C2‐C10 olefins besides a number of C14‐pheromones and volatile terpenes is given and the results discussed. The separation is mainly governed by the type and number of double bonds (isolated, conjugated or aromatic), their steric accessibility (number and size of substituents) for complexation with silver(I) ions, the relief of inherent strain upon complexation and electron donating or withdrawing groups, or polar groups close to the double bond. Polar groups such as hydroxyls also complex weakly with silver. Other functional groups, including carbonyls, and the overall polarity of the solute play only a minor role. Similarly most solvents have only a limited influence on the selectivity and speed of separation, and function more as a transportation medium as in gas chromatography. A comparative model which gives semi‐quantitative estimations of the retention time of most volatile olefins in methanol is presented. Substituent parameters (Ags) which quantitatively forecast the influence of different alkyl side chains are part of this model.

Structurally Characterized Coinage‐Metal–Ethylene Complexes

“…[74][75][76]119] [77] Silver salts are used in the chromatographic separation of alkenes [15,16,31] and play an interesting role in plant-biologyrelated areas such as in preventing ethylene-induced wilting of plant products like cut flowers. [7,9,11,14] In addition, there are numerous spectroscopic investigations and computational studies of Ag I -(C 2 H 4 ) adducts.…”

“…The DewarChatt-Duncanson model of olefin bonding was motivated in large part by a desire to understand the bonding in transition-metal-alkene adducts such as those of silver(I). [4][5][6] The complexes between coinage metals (Cu, Ag, Au) and alkenes also figure prominently in a number of significant application areas ranging from biochemistry, [7][8][9][10][11][12][13][14] chroma-tographic separations, [15,16] olefin-paraffin separations, [17][18][19][20][21][22][23] computational and spectroscopic and kineticthermodynamic studies, to modern organic synthesis, [70][71][72][73] and in several industrial catalytic processes. [74] For example, copper-ethylene adducts are of interest as models for the ethylene (the smallest plant hormone) receptor site in plants.…”

Sex pheromone communication from a population resistant to mating disruptant of the smaller tea tortrix, Adoxophyes honmai Yasuda (Lepidoptera: Tortricidae)

“…These chemicals were more than 99% pure after purification with an HPLC column on a Nucleosil 5SA (250ϫ4.6 mm I.D.) column loaded with Ag ions (van Beek and Subrtova, 1995). Each chemical was diluted with n-hexane, and hexane solution blends of (Z)-9-and (Z)-11-tetradecenyl acetate were prepared.…”

Natural Deuterium Distribution in Fatty Acids Isolated from Peanut Seed Oil: A Site-Specific Study by Quantitative 2H NMR Spectroscopy

“…[10] Furthermore, they can be separated on the basis of their degree of unsaturation by argentation chromatography. [17,18] In this paper, the isotopic distribution of 2 H between different fatty acids isolated from the same biological origin is reported. The approach developed has allowed a direct comparison of the nonstatistical distribution of 2 H within a single fatty acid population to be studied for the first time.…”