Phosphonic Acid Groups

In choosing a SAM system for surface engineering, there are several options. Silane monolayers on hydroxylated surfaces are an option where transparent or nonconductive systems are needed. However, trichlorosilane compounds are moisture-sensitive and polymeri2e in solution. The resulting polymers contaminate the monolayer surface, which occasionally has to be cleaned mechanically. CarboxyUc acids adsorb on metal oxide, eg, AI2O2, AgO through acid—base interactions. These are not specific therefore, it would be impossible to adsorb a carboxyUc acid selectively in the presence of, for example, a terminal phosphonic acid group. In many studies SAMs of thiolates on Au(lll) are the system of choice. 

Surfactants which contain carboxylic acid ester or amide chains with terminal phosphonic acid groups are prepared from polyhydroxystearic acid or poly-caprolactone. Such reaction products are useful as dispersants, emulsifiers, and, in some cases, bactericides, disinfectants, and antiseptics see Sec. III.C.9 [69]. 

Sulfoxides without amino or carboxyl groups have also been resolved. Compound 3 was separated into enantiomers via salt formation between the phosphonic acid group and quinine . Separation of these diastereomeric salts was achieved by fractional crystallization from acetone. Upon passage through an acidic ion exchange column, each salt was converted to the free acid 3. Finally, the tetra-ammonium salt of each enantiomer of 3 was methylated with methyl iodide to give sulfoxide 4. The levorotatory enantiomer was shown to be completely optically pure by the use of chiral shift reagents and by comparison with a sample prepared by stereospecific synthesis (see Section II.B.l). The dextrorotatory enantiomer was found to be 70% optically pure. 

Key words Ion exchange fiber, bifunctional fiber, sulfonic acid groups, phosphonic acid groups. 

Of interest is the metal ion selectivity of bifunctional exchangers having both sulfonic and phosphonic acid groups, since phosphonic acid resins prefer Pb(II) to Ba(II) but sulfonic acid resins show the reversed metal ion selectivity. 

Pb(II) but phosphonic acid groups does not prefer Pb(II). As shown here, the bifunctional FPS-c shows characteristic pH profiles in uptake of Pb(II) and Ba(H) different from those of monofunctional exchangers containing only either of phosphonic acid and sulfonic acid groups. 

Yamabe, K., Ihara, T., Jyo, A., Metal ion selectivity of macroreticular chelating cation exchange resins with phosphonic acid groups attached to phenyl groups of a styrene-divinylbenzene copolymer matrix, Sep. Sci. Technol. 36,2001,3511-3528. 

Schmidt-Naake, G., Bohme, M. and Cabrera, A. 2005. Synthesis of proton exchange membranes with pendent phosphonic acid groups by irradiation grafting of VBC. Chemical Engineering and Technology 28 720-724. 

Miyatake, K. and Hay, A. S. 2001. New poly(arylene etherjs with pendant phosphonic acid groups. Journal of Polymer Science Part A 39 3770-3779. 

Figure 40. Synthesis of poly(arylene ether)s bearing phosphonic acid groups. ...

This specifity is dependent on the acidity of the catalyst, and was studied using the heterogeneous catalysts sulfonated and phosphonated poly benzene, and the homogeneous catalysts paratoluenesulfonic acid and phosphoric acid. The differences between the sulfonic and phosphonic acid groups were greater than the differences between heterogeneous and homogeneous phase, in spite of a considerable difference in reaction temperature. It was thus shown that for a typical Class A reaction, the type of acidity is more important than the physical state of the catalyst. These acidic catalysts were extremely active, and had to be partially neutralized in order to obtain reasonable rates ans selective reactions. 

The BOP- or PyBOP-mediated SPPS of phosphinot or phosphono peptides can be carried out without protecting the phosphinic or phosphonic acid group. Indeed, phosphinic acids are activated, but the P—N bond is not formed. Phosphonic acids are also acti-vatedt and in fact an amide of methyl phenylphosphonic acid has been obtained, however, in the case of protected a-amino phosphonic acids, phosphonamides are only obtained by using AT-phthalyl protection. Side-chain unprotected phosphorylated tyrosine [Tyr(P03H2)] can be coupled by solid-phase synthesis using BOP (PyBOP), but pyrophosphate formation is also observed and some particular Tyr(P)-peptide syntheses are prone to total failure. ... 

Both the 2-deoxy-2-H- (146) [160] and 2-deoxy-2,3-didehydro- (147) [168] Neu5Ac analogues with a phosphonic acid group in place of the carboxyl group have been synthesised by Vasella and coworkers. Steps in the synthesis of the 2-deoxy-2,3-didehydro analogue 147 [168] are shown in Scheme 13. The initial step was the bromohydroxylation of protected 2-deoxy-2,3-didehydro Neu5Ac. 

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