Calcium hydrolysis constant

The data reported, or recalculated in the present review, for the first hydrolysis constant of calcium (CaOH ) are listed in Table 7.18. In those cases where the stability constants have been re-evaluated in the present work from solubility data as a function of ionic strength, only the zero ionic strength value is listed in the table. The remaining data are, however, discussed later. 

A calcium ion indicator dye (based on the structure of the chelator EGTA) that exhibits a strong fluorescence at 385 nm and can be used to measure changes in intracellular Ca concentration. The approximate dissociation constant for the Ca -Fura-2 complex is 0.1 juM, depending on cellular ion composition and pH. An esteri-fied derivative of Fura-2 readily crosses the peripheral membrane of many cells and, after hydrolysis, the release of Fura-2 permits calcium ion measurements within cells. See Calcium Ion Indicator Dyes Metal Ion Complex-ation... 

Catalytic effects.—Within certain limits, the stimulating action exerted by the presence of hydrochloric acid upon the speed of inversion of cane sugar 28 is less the more dil. the acid. Thus, W. Ostwald found the velocity constant with a soln. containing a mol. of acid per 2 litres of soln. is 20 52 per 10 litres, 3 335 and per 100 litres, 0 3128. The action is favoured by the presence of neutral salts, and this the more, the lower the mol. wt. of the salt in the same family group of the periodic system. The temp, coeff. of the inversion is 17 92 at 100°, and. 0 04104 at 25°. W. Ostwald, R. Hopke, and H. Trey have likewise studied the accelerating influence of the acid on the hydrolysis of methyl and ethyl acetates. Similar studies have been made by W. Ostwald and A. Villiers on the hydrolysis of methyl and ethyl acetates, calcium oxalate, and ethyl bromide and iodide. 

The pH dependence of die interconversion kinetics, equilibrium, and solubilities of die lactone and hydroxyacid forms of calcium (R-(R, R ) )-2-(4-duorophenyl)-p,5-dihydroxy-5-(l-methylethyl)-3-phenyl- 4r((phenylamino)-carbonyl)-lH-pyrrole-l-heptanoate (CI-981 atorvastatin calcium) are described. Over a pH range of 2.1-6.0 and at 30 °C, the apparent solubility of die sodium salt of CI-981 increases about 60-fold, and die profile yields a pKa for die terminal carboxyl group of 4.46. In contrast, over a pH range of 2.3-7.7 at the same temperature, die apparent solubility of die lactone form of CI-981 varies lidle, and die mean solubility is 1.34 meg/ml. The kinetics of interconversion and die equilibrium between the hydroxyacid and lactone forms have been studied as a function of pH, buffer concentration, and temperature at a fixed ionic strength. The rate constant for lactone formation is well described by specific acid-catalyzed and spontaneous lactonization padiways, whereas die rate constant for lactone hydrolysis is well described by specific acid-, water-, and specific base-catalyzed padiways."... 

Protons are pumped in living systems to establish a proton gradient, and the energy necessary for this pumping is frequently provided by the hydrolysis of ATP, in which ADP and phosphate are formed [7]. In this section, we study a model of a proton pump found in the plasma membrane of plants [8-12] and include the coupling of potassium and calcium ion transport. As in prior examples, we calculate the thermodynamic efficiency [13] of the proton pump with a constant influx of ATP and compare that to the thermodynamic efficiency with an oscillatory influx of ATP, the average of which is the same as the constant concentration of ATP. 

For example, hydrolysis of a solution of 2-chloro-2-methylpropane gives the expected 2-methyl-2-propanol (ferf-butyl alcohol), with a rate constant Quite a different result is obtained when the same experiment is carried out in the presence of the soluble salt calcium formate 1,1-Dimethylethyl formate (terf-butyl formate) replaces the alcohol as the product, but the reaction still proceeds at exactly the same rate ki. In this case, formate ion, a better nucleophile than water, wins out in competition for bonding to the intermediate carbocation. The rate of disappearance of the starting material is determined by ki (regardless of the product eventually formed), but the relative yields of the products depend on the relative reactivities and concentrations of the competing nucleophiles. 

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