Medium effect on the second-stage dissociation constant of N-(2-acetamido)imino diacetic acid (H2ADA)

1992 ◽  
Vol 70 (6) ◽  
pp. 1684-1687 ◽  
Author(s):  
Ahmed Hassan ◽  
H. A. Azab ◽  
S. A. El Gyar ◽  
Z. A. Khafagy
Keyword(s):  
Dissociation Constant ◽  
Aqueous Media ◽  
Acid Dissociation ◽  
Medium Effect ◽  
Solvent Mixtures ◽  
Diacetic Acid ◽  
Imino Group ◽  
Second Stage ◽  
Dissociation Equilibrium ◽  
Imino Diacetic Acid

The second-stage dissociation constant values of N-(2-acetamido)imino diacetic acid (H2ADA) were determined at 25 ± 0.1 °C by potentiometric titration in different mixed-solvent mixtures (methanol, ethanol, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, and dioxane). It was observed that the pKa value is slightly influenced as the solvent is enriched in methanol and ethanol, and remains practically constant in the presence of different amounts of DMF and DMSO. A prounounced change in the pKa value was observed as the solvent is enriched in acetone or dioxane. These results are discussed in terms of various solvent characteristics. It is concluded that the electrostatic effect has only a relatively small influence on the dissociation equilibrium of the imino group [Formula: see text]. Other solvent effects such as solvent basicity, different stabilization of the free base of the conjugate acid by hydrogen bonding interactions in aquoorganic solvent media relative to pure aqueous media, as well as proton–solvent interaction play an important role in the acid dissociation equilibrium.

Medium Effect on the Second-Stage Dissociation Constant of N,N-Bis(2-hydroxyethyl)glycine

1994 ◽  
Vol 39 (3) ◽  
pp. 599-601 ◽  
Author(s):  
H. A. Azab ◽  
Z. A. Khafagy ◽  
Ahmed Hassan ◽  
A. M. El-Nady
Keyword(s):  
Dissociation Constant ◽  
Medium Effect ◽  
Second Stage

Accurate acid dissociation constant (pKa) calculation for the sulfachloropyridazine and similar molecules

2021 ◽  
Vol 27 (8) ◽  
Author(s):  
Fernando Marques Carvalho ◽  
Yuri Alves de Oliveira Só ◽  
Alessandra Sofia Kiametis Wernik ◽  
Mônica de Abreu Silva ◽  
Ricardo Gargano
Keyword(s):  
Dissociation Constant ◽  
Acid Dissociation ◽  
Acid Dissociation Constant ◽  
Pka Calculation

Dissociation of imino proton(s) of a highly water-soluble metal-free phthalocyanine and determination of its pKa value in water

2013 ◽  
Vol 17 (06n07) ◽  
pp. 447-453 ◽  
Author(s):  
Hiroaki Isago ◽  
Harumi Fujita
Keyword(s):  
Aqueous Media ◽  
Thermal Reaction ◽  
Water Soluble ◽  
Acid Dissociation ◽  
Acid Dissociation Constant ◽  
Metal Free ◽  
Imino Proton ◽  
Pka Value ◽  
Triton X

Dissociation of imino proton(s) in the cavity of the macrocycle of a highly water-soluble, metal-free phthalocyanine ( H 2( H 4 tsppc ); where H 4 tsppc denotes tetrakis{(2′,6′-dimethyl-4′-sulfonic acid)phenoxy}phthalocyaninate) in ethanolic and aqueous solutions has spectrophotometrically been investigated. The spectral changes associated with reaction with NaOH have been found to involve one-proton transfer process in aqueous media while two-protons process in ethanolic media. The acid-dissociation constant of the first imino proton in water (in the presence of Triton X-100) has been determined to be 12.5 ± 0.2 (as pKa) at 25 °C. The doubly deprotonated species in EtOH has been easily converted to its corresponding cobalt(II) derivative by thermal reaction with anhydrous CoCl 2.

scholarly journals pKa and Ka (Acid dissociation constant)

2020 ◽  
pp. S108-S108
Author(s):  
G Manjooran
Keyword(s):  
Dissociation Constant ◽  
Acid Dissociation ◽  
Acid Dissociation Constant

pKa of a drug is the pH at which 50% of the drug is ionised and 50% is not ionised/unionised. The pKa is specific for each drug and these properties determine how a drug can be administered, the speed of absorption as well as speed of excretion by the kidneys.

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