Hydrolysis of cations. Formation constants and standard free energies of formation of hydroxy complexes

1983 ◽  
Vol 22 (16) ◽  
pp. 2297-2305 ◽  
Author(s):  
Dennis W. Barnum
Keyword(s):  
Formation Constants ◽  
Free Energies ◽  
Hydrolysis Of

scholarly journals Unexpected Resistance to Base-Catalyzed Hydrolysis of Nitrogen Pyramidal Amides Based on the 7-Azabicyclic[2.2.1]heptane Scaffold

Molecules ◽  
2018 ◽  
Vol 23 (9) ◽  
pp. 2363 ◽  
Author(s):  
Diego Ocampo Gutiérrez de Velasco ◽  
Aoze Su ◽  
Luhan Zhai ◽  
Satowa Kinoshita ◽  
Yuko Otani ◽  
...  
Keyword(s):  
Nitrogen Atom ◽  
Amide Bond ◽  
Free Energies ◽  
Amide Nitrogen ◽  
Bond Rotation ◽  
Entropy Term ◽  
And Inversion ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Amide Nitrogen Atom

Non-planar amides are usually transitional structures, that are involved in amide bond rotation and inversion of the nitrogen atom, but some ground-minimum non-planar amides have been reported. Non-planar amides are generally sensitive to water or other nucleophiles, so that the amide bond is readily cleaved. In this article, we examine the reactivity profile of the base-catalyzed hydrolysis of 7-azabicyclo[2.2.1]heptane amides, which show pyramidalization of the amide nitrogen atom, and we compare the kinetics of the base-catalyzed hydrolysis of the benzamides of 7-azabicyclo[2.2.1]heptane and related monocyclic compounds. Unexpectedly, non-planar amides based on the 7-azabicyclo[2.2.1]heptane scaffold were found to be resistant to base-catalyzed hydrolysis. The calculated Gibbs free energies were consistent with this experimental finding. The contribution of thermal corrections (entropy term, –TΔS‡) was large; the entropy term (ΔS‡) took a large negative value, indicating significant order in the transition structure, which includes solvating water molecules.

Bioenergetics of Na+ transport across frog skin: chemical and electrical measurements

1983 ◽  
Vol 245 (6) ◽  
pp. F691-F700 ◽  
Author(s):  
M. M. Civan ◽  
K. Peterson-Yantorno ◽  
D. R. DiBona ◽  
D. F. Wilson ◽  
M. Erecinska
Keyword(s):  
Free Energy ◽  
Frog Skin ◽  
Atp Hydrolysis ◽  
Transepithelial Transport ◽  
Base Line ◽  
Free Energies ◽  
Electrical Measurements ◽  
Far From Equilibrium ◽  
The Difference ◽  
Hydrolysis Of

Enzymatically prepared split frog skins consisted purely of epithelial cells. Electrical parameters and the cell contents of ATP, ADP, phosphocreatine (PCr), creatine, inorganic phosphate, protein, and water were measured in skins maintained at room temperature. Studies were conducted under base-line conditions, 15 and 60 min after adding vasopressin, and 30 min after adding amiloride. Intracellular ionic activities and concentrations were obtained from previous results. The data demonstrated that 1) the base-line concentration ratio of PCr/ATP was 0.53 +/- 0.03; 2) the average molar free energy of hydrolysis of intracellular ATP was approximately 15.0 kcal X mol-1 under control conditions, changing by less than or equal to 3% with changes in transport; and 3) the free energy of extruding 3 mol of Na+ and accumulating 2 mol of K+ was approximately 9.8 kcal X mol-1 under base-line conditions; the difference between the molar free energies of ATP hydrolysis and of transport work remained large, despite large changes in transepithelial transport. The simplest conclusion is that the Na+ pump of frog skin operates far from equilibrium.

scholarly journals Complexation parameters for the actinides(IV)-humic acid system: a search for consistency and application to laboratory and field observations

2008 ◽  
Vol 96 (6) ◽  
Author(s):  
Pascal E. Reiller ◽  
Nick D. M. Evans ◽  
Gyula Szabó
Keyword(s):  
Original Data ◽  
Formation Constants ◽  
Field Observations ◽  
Independent Data ◽  
Acid System ◽  
Hydrolysis Constant ◽  
Independent Laboratory ◽  
System A ◽  
Hydrolysis Of ◽  
Full Analogy

SummaryThe coherence of actinide(IV) complexation by humic substances (HS) is reviewed and new data are proposed. In a first attempt, the values of independent data from literature on Th(IV), U(IV), and Pu(IV) are collected, selected, and compiled. The data obtained follow the “classical” trend of increasing conditional formation “constants” with pH, led both by the increasing ionisation of HS and by the extensive hydrolysis of the tetravalent actinides. Even though a fair agreement is evident, the experimental uncertainties do not permit a full analogy between the actinides(IV) to be ascertained. In a second attempt, the experiments from which the original data are available were reinterpreted using only one hydrolysis constant set for U(IV) as an example, considering that all actinides(IV) have analogous humic complexation behaviour. Hence, the obtained evolution of conditional formation “constants” is much more coherent and the uncertainties do not permit to distinguish an actinide(IV) from one another. The obtained data are then applied to independent laboratory and

The role of ATP in the reactions of type II DNA topoisomerases

2010 ◽  
Vol 38 (2) ◽  
pp. 438-442 ◽  
Author(s):  
Andrew D. Bates ◽  
Anthony Maxwell
Keyword(s):  
Atp Hydrolysis ◽  
Dna Gyrase ◽  
Dna Topology ◽  
Type Ii ◽  
Free Energies ◽  
Dna Topoisomerases ◽  
Type Ii Dna Topoisomerases ◽  
Topology Simplification ◽  
Hydrolysis Of

Type II DNA topoisomerases catalyse changes in DNA topology in reactions coupled to the hydrolysis of ATP. In the case of DNA gyrase, which can introduce supercoils into DNA, the requirement for free energy is clear. However, the non-supercoiling type II enzymes carry out reactions that are apparently energetically favourable, so their requirement for ATP hydrolysis is not so obvious. It has been shown that many of these enzymes (the type IIA family) can simplify the topology of their DNA substrates to a level beyond that expected at equilibrium. Although this seems to explain their usage of ATP, we show that the free energies involved in topology simplification are very small (<0.2% of that available from ATP) and we argue that topology simplification may simply be an evolutionary relic.

Hydrolysis of dimethylphenyltin(IV) and triphenyltin(IV) chlorides in different aqueous ethanol solutions

2008 ◽  
Vol 86 (8) ◽  
pp. 751-756 ◽  
Author(s):  
Morteza Jabbari ◽  
Farrokh Gharib ◽  
Mostafa Mohammadpour Amini ◽  
Amirreza Azadmehr
Keyword(s):  
Hydrogen Bond ◽  
Aqueous Ethanol ◽  
Formation Constants ◽  
Single Parameter ◽  
Hydrogen Bond Donor ◽  
Hydrogen Bond Acceptor ◽  
Polarity Parameter ◽  
Wide Ph Range ◽  
Hydrogen Bond Acceptor Basicity ◽  
Hydrolysis Of

The hydrolysis of [(Me)2(Ph)Sn(IV)]+ and [(Ph)3Sn(IV)]+ has been investigated at 25 °C and different aqueous solutions of ethanol, using a combination of spectrophotometric and potentiometric techniques. The species formed together with their formation constants have been determined using the computer program Squad over a wide pH range of 1 to 11. The hydrolysis constants in different media were analyzed in terms of Kamlet and Taft parameters. Single-parameter correlation of the formation constants, K11 and K12, versus α (hydrogen-bond donor acidity), β (hydrogen-bond acceptor basicity), and π* (dipolarity/polarizability) for both cases are relatively poor in all solutions, but multiparameter correlation represents significant improvement with regard to the single-parameter models. In this work, we have also used the normalized polarity parameter, ETN, alone and in combination with the Kamlet–Taft parameter to find a better correlation of the formation constants in different aqueous ethanol solutions.Key words: dimethylphenyltin(IV) chloride, triphenyltin(IV) chloride, hydrolysis constant, aqueous ethanol solutions, solvent effect.

scholarly journals CONDUCTOMETRIC STUDY OF COMPLEX FORMATION BETWEEN 2,3-PYRAZINEDICARBOXYLIC ACID AND SOME TRANSITION METAL IONS IN METHANOL

2012 ◽  
Vol 20 (20) ◽  
pp. 43-50
Author(s):  
A.A. El-Khouly ◽  
E. A. Gomaa ◽  
S. E. Salem
Keyword(s):  
Complex Formation ◽  
Transition Metal Ions ◽  
Formation Constants ◽  
Molar Conductance ◽  
Association Constants ◽  
Absolute Methanol ◽  
Free Energies ◽  
Titration Curves ◽  
Conductometric Study ◽  
Complexation Reactions

The complexation reactions between CuCl2 CoCL2 and NiCL2 with 2,3-Pyrazinedicarboxylic acid in methanol (MeOH) at 313.15 K were studied by conductometric methods. The association constants, formation constants and Gibbs free energies were calculated from the conduclometric titration curves. On drawing the relation between molar conductance and the ratio of metal to ligand coflCentrations, different lines were obtained indicating the formation of 1: 1 and 2: 1 (M:L) stoichiometric complexes. The formation constants and Gibbs free energies of different complexes in absolute Methanol at 313.15 Kfollow the order:

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