Riyad R Irani

Synthesis and properties of mono- and poly-methylene-diphosphonic acids and esters

Abstract A series of methylenediphosphonic acids, (HO)2OP(CH2)nPO(OH)2, (n = 1, 2, 3, 4, 5, 6 and 10) have been prepared by hydrolysis of the corresponding tetra-ethyl esters. The esters with n ⩾ 3 were obtained by either a Michaelis-Becker or an Arbuzov-Michaelis type reaction. For n = 1 or 2, a modified Michaelis-Becker reaction was utilized. The 31P nuclear magnetic resonance chemical shifts as well as the infra-red spectra show that as n increases the effect of the two end phosphorus atoms on one another decreases, and becomes very small for n > 3. The X-ray diffraction patterns of the diphosphonic acids are reported.

Quantitative applications of high-resolution proton magnetic resonance measurements in the characterization of detergent chemicals

Quantitative hydrogen nuclear magnetic resonance measurements are used for the determination of average structures of detergent chemicals. For alkylbenzenes, alkylphenols, and ethylene oxide (EO) adducts of alkylphenols, the following quantities can be measured: average lengths of alkyl chains, average molecular weights, degree and kind of branching in the alkyl chain, ortho-para distribution of aryl substituents, and average lengths of BO chains. Accuracy is of the the order of ± 2% of the total hydrogen. The method is nondestructive, and sample volumes as small as 0.007 ml have been used.

Iron sequestration by polyphosphates

The equilibrium sequestration of ferric and ferrous iron by polyphosphates has been measured at room temperature in the pH range of 4–11. In general, sequestration decreases with increase in pH or increase in the chain length of the polyphosphate. The dissociation constants of ferric pyrophosphate and ferric tripolyphosphate have been estimated to be around 10−23. The polyphosphates form weaker ferrous complexes. *** DIRECT SUPPORT *** A03O2199 00003

Metal complexing by phosphorus compounds—IX: Thermodynamics of ionization of ortho-, pyro- and tripolyphosphoric acids

The ΔH of ionization of H3PO4, H4P2O7 and H5P3O10 have been determined calorimetrically at 25°. Values at several ionic strengths were extrapolated to infinite dilution, permitting calculation of ΔS° of ionization. A calorimetric technique is described for determining the ionization constants of very strong acids, use of which gave values of 0·36 and 0·3 for the ionizations H4P2O7 ⇌ H+ + H3P2O7− and H5P3O10 ⇌ H+ + H4P3O10−, respectively. The values of ΔH° of ionization were found to change successively from endothermic to exothermic to more exothermic as the pK values of ionization decreased. The values of ΔS° of ionization were found to be large negative numbers that can be reasonably accounted for by changes in hydration numbers that accompany ionization. It is also shown that the following equation represents the calculated ΔS° values of ionization of phosphoric acids on a mole fraction standard state, corrected for the difference of the symmetry numbers of the acid and conjugate base: ΔS°cor. = a − {b[(Z + 1)2 − Z2]r} where Z and r are the charge and crystal radius of the unioniz species.

On the ΔH and ΔS of metal ion interaction with substituted methylene diphosphonates

Abstract The Ca2+ and Mg2+ complexing constants with a series of substituted methylene diphosphonates have been determined at 25° in 0·5 M tetramethylammonium chloride. The enthalpies of Ca2+, Li+, Na+, and K+ complexing by substituted methylene diphosphonates have been measured calorimetrically. The Δ S values of complexing of a given metal ion is shown to be remarkably constant with diphosphanates, and proportional to Z 2 r . Variations in the Δ G values of complexing are attributed to differences in the Δ H term.

Metal complexing by phosphorus compounds—VIII complexing of tin (II) by polyphosphates

Abstract The stability of complexes of pyrophosphate and tripolyphosphate ions with Sn(II), which occur in the pH region 5–7, have been determined by equilibrating phosphate solutions at unit ionic strength with solid SnO at 25°C. The following formation constants were calculated for the simplest equilibria that are consistent with the data: where x is one or two. Also, The constant for the hydrolysis reaction was also measured: The trend of the Sn(II) complexing by long chain polyphosphates with average chain lengths up to fourteen is discussed.