Partition constants of α-aminophosphonates in two-phase aqueous-organic solvent systems

Abstract

Two-phase potentiometric titration was used to determine partition constants for a series of a-aminophosphonates (RO) 2 P(O)CH 2 NR 1 R 2 [R = Alk (C 2 3C 5 ), R 1 , R 2 = Me, Et, (CH 2 ) 5 ] between water and organic solvents, such as chloroform, carbon tetrachloride, toluene, octane, n-octanol, nitrobenzene, o-xylene, and cyclohexane. Correlations between the partition constants and the number of carbon atoms in substrate molecules were obtained. Solvent effects on partition constants were discussed, and solution parameters of a-aminophosphonates were calculated.The fast recent progress of the chemistry of aminophosphoryl compounds is primarily connected with their extensive practical use. Being structural analogs of proteinogenic amino acids, they proved to be highly effective biologically active compounds with a broad-spectrum activity [133].Though the biological activity of aminophosphosphoryl compounds is a very attractive feature, some other field of practical use of this type of phosphorus compounds have recently been recognized. Among a-aminophosphonates, highly effective extractants, complex-forming agents, membrane transporters, ionophores, and some other reagents whose activity is based on the complex-forming ability of aminophosphonates have been found [1].Previously we described [438] methods of synthesis of new compounds containing one or two aaminophosphoryl groups, studied their acid3base properties, and demonstrated their use for extraction and analysis of metal ions. Extractive properties of these compounds present undoubted interest for searching new highly effective analytical and transport reagents. The possibility of wide variation of the nature of substituents at the reaction centers of the alkylaminophosphoryl skeleton of these compounds. i.e. phosphorus, a-carbon, and nitrogen, renders them promising objects for research into the effect of structural factors on extractive and other important properties.At the same time, of great importance for studying mechanisms of liquid-phase and membrane extraction, developing technology of purification of aminophosphonates, and predicting their biological activity are quantitative data on the behavior of these compounds in two-phase aqueous3organic solvent systems.In this connection we set ourselves the aim to determine the partition constants of aminophosphonates containing alkyl and heterocyclic (piperidyl) fragments, in two-phase systems comprising water and organic solvents of different nature.Aminophosphonates I3IX were prepared by Kabachnik3Fields reaction [1] in a ternary system comprising a dialkyl hydrogen phosphite, formaldehyde, and a carbonyl compound. Characteristics of newly synthesized phosphonates are presented in [5]. E I!IXR 1 = n-Pr, R 2 = R 3 = Me (I); R 1 = n-Bu, R 2 = R 3 = Me (II); R 1 = Et, R 2 = R 3 = Et (III); R 1 = n-Pr, R 2 = R 3 = Et (IV); R 1 = n-Bu, R 2 = R 3 = Et (V); R 1 = Et, R 2 + R 3 = (CH 2 ) 5 (VI); R 1 = n-Pr, R 2 + R 3 = (CH 2 ) 5 (VII); R 1 = i-Pr, R 2 + R 3 = (CH 2 ) 5 (VIII); R 1 = Et, R 2 = CH(CH 3 ) 2 , R...

Liquid Extraction of Noble Metal Ions with an α-Amino Phosphonate

“…We observed linear correlations between the distribution constant and number of carbon atoms in the amino phosphonate molecule, irrespective of particular organic phase. The regression equations obtained [6] show that the logarithm of the distribution constant of amino phosphonates containing more than 20 carbon atoms exceeds 6, i.e., the extractant loss due to its transfer to the aqueous phase will be negligible.When choosing the particular extractant, we also took into account its chemical stability. As shown in [7], amino phosphonates containing a primary or secondary nitrogen atom tend to disproportionate when kept for a long time in a condensed phase.…”

“…We observed linear correlations between the distribution constant and number of carbon atoms in the amino phosphonate molecule, irrespective of particular organic phase. The regression equations obtained [6] show that the logarithm of the distribution constant of amino phosphonates containing more than 20 carbon atoms exceeds 6, i.e., the extractant loss due to its transfer to the aqueous phase will be negligible.…”

“…The results obtained served as a basis for choosing an a-amino phosphonate suitable for commercial applications. In particular, we determined the distribution constants in water3organic solvent systems of a-amino phosphonates containing various organic groups at the P, C, and N atoms of the aminomethylphosphonate moiety [6]. We observed linear correlations between the distribution constant and number of carbon atoms in the amino phosphonate molecule, irrespective of particular organic phase.…”

Synthesis of β-Aminophosphonates and Study of Their Acid-Base Properties and Phase Distribution in Water-Organic Solvent Systems

“…Variation of substituents at the phosphorus, -carbon, and nitrogen atoms over a wide range showed that the most selective extractants were those aminophosphoryl reagents which contained more than 20 carbon atoms; in this case, the optimal hydrophilic-lipophilic balance was achieved. It should be emphasized specially that the above information was deduced by analysis of correlations between the number of carbon atoms in the extractant molecules and their distribution constants in waterorganic solvent systems [7]. Therefore, the latter parameter is necessary to elucidate the structure-property relations with a view to effect subsequent purposeful synthesis of extractants, bioactive, and other potentially useful substances possessing an optimal combination of the desired characteristics.…”

Liquid Extraction of Inorganic Acids with α-Aminophosphoryl Compounds

“…The extraction coefficients were calculated by Gran's linearization of the titration curves, as we previously described for phase distribution of a-aminophosphonates [4]. The resulting log extraction constants are listed in the table.…”