Salicylic acid condensation type

Phenolic ion exchangers derived from a phanol-formaIdehyde condensation reaction appeared in the first generation of ion-exchenge polymers. More recently, styrene-divinylbenzene copolymers incorporating azo-subslituied cresul and salicylic acid, catechol, hydroquinone. and benzoquinone bave been described, The quinone-type polymers selectively sorb Hg(lil) and the catechol reains sorb CtfVl). 

Figure 5.1 Change in transport number of calcium ions relative to sodium ions, mobility ratio and ion exchange equilibrium constant between calcium ions and sodium ions in a cation exchange membrane having salicylic acid groups as cation exchange groups (condensation type) with the pH of a mixed salt solution. (O) PNaC i (A) KNaCa ( ) UCu/UNa. Electrodialysis of the mixed solution of 0.375 N sodium chloride and 0.125 N calcium chloride (chloride ions 0.500 N), the pH of which was adjusted, was carried out using a cation exchange membrane prepared from condensation polymerization of salicylic acid, phenol and formaldehyde.

The most intensively studied types of (poly)condensation studied before World War 1 were reactions between phenols and aldehydes. The interest in this field of chemistry like the interest in reactions of salicylic acid was partially motivated by the fact that extracts from the bark of willow trees have a pain-stilling effect (what was already known to the ancient Greeks). From willow trees and other plants... 

Somewhat different type 2-amino-4H-chromene synthesis is represented by the interaction of CH-acidic nitriles 27 with salicylic aldehyde 157 where the phenolic OH and aldehyde groups are present in the same molecule. A conventional mechanistic scheme is represented (Scheme 58), where in the presence of a base nitrile 27 condenses with the aldehyde to give Knoevenagel intermediate 158. Then nucleophilic addition of the OH group leads to iminochromene 159, which then adds a nucleophile (as a rule, the second equivalent of nitrile 27) at position 4 to form 2-amino-4H-chromene 160. 

Mn compounds of several types of terdentate Schiff base ligands are known.Of interest for supposed biological reasons are ligands of donor set O—N—O derived from condensation of (x-amino acids with salicylaldehyde," pyruvic acid/" pyridoval and substituted salicylal-dehydes/ " Although X-ray analysis " indicates that the compound [Mn (pyridoxal-valine)2] is octahedral, the structures of most of these compounds have not been fully elucidated. Claims of monomeric, dimeric and polymeric molecules are based mainly upon analytical results and upon room temperature magnetic susceptibility measurements. Nothing of special biological interest has come from this work. 

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