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In chemistry, biochemistry, and pharmacology, a dissociation constant (K D) is a specific type of equilibrium constant that measures the propensity of a larger object to separate (dissociate) reversibly into smaller components, as when a complex falls apart into its component molecules, or when a salt splits up into its component ions.
Between the two buffer regions there is an end-point, or equivalence point, at about pH 3. This end-point is not sharp and is typical of a diprotic acid whose buffer regions overlap by a small amount: pK a2 − pK a1 is about three in this example. (If the difference in pK values were about two or less, the end-point would not be noticeable ...
Speciation of ions refers to the changing concentration of varying forms of an ion as the pH of the solution changes. [1]The ratio of acid, AH and conjugate base, A −, concentrations varies as the difference between the pH and the pK a varies, in accordance with the Henderson-Hasselbalch equation.
This equation can be used to calculate the value of log K at a temperature, T 2, knowing the value at temperature T 1. The van 't Hoff equation also shows that, for an exothermic reaction ( Δ H < 0 {\displaystyle \Delta H<0} ), when temperature increases K decreases and when temperature decreases K increases, in accordance with Le Chatelier's ...
log 10 β values between about 2 and 11 can be measured directly by potentiometric titration using a glass electrode. This enormous range of stability constant values (ca. 100 to 10 11) is possible because of the logarithmic response of the electrode. The limitations arise because the Nernst equation breaks down at very low or very high pH.
The equilibrium is not complete because the acidity difference between guanidinium and water is not large. The approximate pK a values: 13.6 vs 15.7. Complete deprotonation should be done with extremely strong bases, such as lithium diisopropylamide. C(NH 2) + 3 Cl − + Li + N(C 3 H 7) − 2 → HNC(NH 2) 2 + HN(C 3 H 7) 2 + LiCl
The Davies equation is an empirical extension of Debye–Hückel theory which can be used to calculate activity coefficients of electrolyte solutions at relatively high concentrations at 25 °C. The equation, originally published in 1938, [ 1 ] was refined by fitting to experimental data.
The carbon with Z is defined as C1(ipso) and fluorinated carbon as C4(para). This definition is followed even for Z = H. The left-hand side of is called CEBE shift or ΔCEBE, and is defined as the difference between the CEBE of the fluorinated carbon atom in p-F-C 6 H 4-Z and that of the fluorinated carbon in the reference molecule FC 6 H 5.