Prediction of acidity constants of some important selenium oxoacids in aqueous solution by computational techniques

RSC Advances ◽  
2014 ◽  
Vol 4 (10) ◽  
pp. 5206 ◽  
Author(s):  
Mostafa Abedi ◽  
Hossein Farrokhpour ◽  
Solaleh Farnia
Keyword(s):  
Aqueous Solution ◽  
Computational Techniques ◽  
Acidity Constants

Inerte Amminkomplexe als mehrwertige Kationsäuren in wäßriger Lösung / Inert Ammine Complexes as Multivalent Cationic Acids in Aqueous Solution

1980 ◽  
Vol 35 (9) ◽  
pp. 1096-1103 ◽  
Author(s):  
Matthias Kretschmer ◽  
Lutwin Labouvie ◽  
Karl-W. Quirin ◽  
Helmut Wiehn ◽  
Ludwig Heck
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Spectrophotometric Method ◽  
Complex Cation ◽  
Aqua Ligand ◽  
Second Step ◽  
Acidity Constants ◽  
Ammine Complexes ◽  
Temperature Variations ◽  
Enthalpy Changes

Acidity constants of ammine complexes of tetravalent platinum in aqueous solutions have been determined by a spectrophotometric method at very low ionic strengths and extrapolated to zero ionic strength. Temperature variations of pK-values (25 °C and 50 °C) yield thermodynamic parameters for two successive deprotonation steps of hexaammineplatinum(IV), pentaamminechloroplatinum(IV), and tris(ethylenediamine)pla- tinum(IV) complexes and for the deprotonation of pentaammineaquacobalt(III) ion.The enthalpy changes for the first and second steps are similar and range from 50 to 75 kJ/mole while for the aqua ligand of Co(III) 33 kJ/mole are found. The very large dif­ference in the entropy changes (about 70 to 80 J/K mole for the first step and -10 to + 20 J/K mole for the second step) is interpreted by a model of solvation change. The primary hydration sphere of strongly oriented and immobilized water dipoles around the highly charged complex cation is transformed to a hydrogen-bonded solvation sheath when the electric field of the complex is weakened upon release of the first proton.

Raman spectroscopic determination of the acidity constants of salicylaldoxime in aqueous solution

2011 ◽  
Vol 42 (3) ◽  
pp. 505-511 ◽  
Author(s):  
M. A. Elbagerma ◽  
H. G. M. Edwards ◽  
Gholamhassan Azimi ◽  
I. J. Scowen
Keyword(s):  
Aqueous Solution ◽  
Spectroscopic Determination ◽  
Acidity Constants ◽  
Raman Spectroscopic

Determination of acidity constants of curcumin in aqueous solution and apparent rate constant of its decomposition

2004 ◽  
Vol 60 (5) ◽  
pp. 1091-1097 ◽  
Author(s):  
Margarita Bernabé-Pineda ◽  
Marı́a Teresa Ramı́rez-Silva ◽  
Mario Romero-Romo ◽  
Enrique González-Vergara ◽  
Alberto Rojas-Hernández
Keyword(s):  
Aqueous Solution ◽  
Rate Constant ◽  
Apparent Rate Constant ◽  
Acidity Constants

Acidity constants of some sulfur oxoacids in aqueous solution using CCSD and MP2 methods

2013 ◽  
Vol 42 (15) ◽  
pp. 5566 ◽  
Author(s):  
Mostafa Abedi ◽  
Hossein Farrokhpour
Keyword(s):  
Aqueous Solution ◽  
Acidity Constants

Solution properties of metal ion complexes formed with the antiviral and cytostatic nucleotide analogue 9-[2-(phosphonomethoxy)ethyl]-2-amino-6-dimethylaminopurine (PME2A6DMAP)

2014 ◽  
Vol 92 (8) ◽  
pp. 771-780 ◽  
Author(s):  
Raquel B. Gómez-Coca ◽  
Astrid Sigel ◽  
Bert P. Operschall ◽  
Antonín Holý ◽  
Helmut Sigel
Keyword(s):  
Aqueous Solution ◽  
Stability Constants ◽  
Metal Ion ◽  
Present System ◽  
Therapeutic Effects ◽  
Solution Properties ◽  
Acidity Constants ◽  
Nucleotide Analogue ◽  
Ether Oxygen ◽  
The Stability

The acidity constants of protonated 9-[2-(phosphonomethoxy)ethyl]-2-amino-6-dimethylaminopurine (H3(PME2A6DMAP)+) are considered, and the stability constants of the M(H;PME2A6DMAP)+ and M(PME2A6DMAP) complexes (M2+ = Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, or Cd2+) were measured by potentiometric pH titrations in aqueous solution (25 °C; I = 0.1 mol/L, NaNO3). In the M(H;PME2A6DMAP)+ species, H+ and M2+ (mainly outersphere) are at the phosphonate group; this is relevant for phosphoryl-diester bridges in nucleic acids because, in the present system, there is no indication for a M2+–purine binding. This contrasts, for example, with the complexes formed by 9-[2-(phosphonomethoxy)ethyl]adenine, M(H;PMEA)+, where M2+ is mainly situated at the adenine residue. Application of log [Formula: see text] vs. [Formula: see text] plots for simple phosph(on)ate ligands, R–PO32− (R being a residue that does not affect M2+ binding), proves that all M(PME2A6DMAP) complexes have larger stabilities than what would be expected for a M2+–phosphonate coordination. Comparisons with M(PME–R) complexes, where R is a noncoordinating residue of the (phosphonomethoxy)ethane chain, allow one to conclude that the increased stability is due to the formation of five-membered chelates involving the ether–oxygen of the –CH2–O–CH2–PO32− residue: the percentages of formation of these M(PME2A6DMAP)cl/O chelates, which occur in intramolecular equilibria, vary between 20% (Sr2+, Ba2+) and 50% (Zn2+, Cd2+), up to a maximum of 67% (Cu2+). Any M2+ interaction with N3 or N7 of the purine moiety, as in the parent M(PMEA) complexes, is suppressed by the (C2)NH2 and (C6)N(CH3)2 substituents. This observation, together with the previously determined stacking properties, offers an explanation why PME2A6DMAP2– has remarkable therapeutic effects.

Acidity constants and reactivities of the benzidine and N,N-dimethylbenzidine dications, the two electron oxidation intermediates of benzidine carcinogens

2000 ◽  
Vol 78 (9) ◽  
pp. 1178-1185
Author(s):  
Robert A McClelland ◽  
Daniel Ren ◽  
Raechelle D'Sa ◽  
Abid R Ahmed
Keyword(s):  
Aqueous Solution ◽  
Oxidation Product ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Chemical Oxidation ◽  
Oxidation Products ◽  
Surprising Result ◽  
Acidity Constants ◽  
Conjugate Acid

This paper describes the behavior in aqueous solutions of the two electron oxidation products of the carcinogens benzidine and N,N-dimethylbenzidine. In biological systems there is evidence that these diamines are oxidized by peroxidases, and that a product of this oxidation may be partly responsible for carcinogenicity. Entry into the oxidation products in the present study was provided through the bis-perchlorate salts of dications obtained upon chemical oxidation and through the irradiation of 4'-amino and 4'-N,N-dimethylamino-4-azidobiphenyls. The benzidine oxidation product exists in three conjugate acid-base forms, a dication, a monocation and neutral bisimine, with pKa(1) = 5.0 and pKa(2) = 9.0. These values stand in marked contrast to ones previously obtained for the two electron oxidation product of p-phenylenediamine, pKa(1) < 1.5 and pKa(2) = 5.75. The dimethylamino derivative, blocked from forming the neutral form, exists as a dication and monocation, with pKa = 5.0. Both systems are quite long-lived in aqueous solution, but they do decay on the minutes-to-hours time scale. The kinetics can be explained by reactions of both the dication and the monocation with water, with a reaction of hydroxide and the monocation becoming important around pH 10. One surprising result is that the monocations are two orders of magnitude more reactive than the dications. Thus, at neutral pH the form that exists in both systems is the monocation, and this is the species that is the most reactive towards the solvent. One of the resonance contributors in the monocation is a 4-biphenylylnitrenium ion. Comparison with other 4'-substituted-4-biphenylylnitrenium ions studied by laser flash photolysis shows that the 4'-amino- and 4'-dimethylamino substituents are highly kinetically stabilizing. These cations, for example, are a billion-fold longer-lived in aqueous solution than the parent 4-biphenylylnitrenium ion.Key words: quinone bisimine, nitrenium, aryl azide.

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