Does pKa apply to bases?
One can use pKa’s to determine the ratio of conjugate acid to conjugate base at any “effective pH”. At a pH above the pKa of an acid, the conjugate base will predominate and at a pH below the pKa the conjugate acid will predominate. At a pH well above the pKa, we say only the conjugate base is stable.
What is the pKa of a base?
pKa is the negative base-10 logarithm of the acid dissociation constant (Ka) of a solution. The lower the pKa value, the stronger the acid. For example, the pKa of acetic acid is 4.8, while the pKa of lactic acid is 3.8.
Does pKa change with solvent?
Some solvents may more efficiently stabilize anions that form when Bronsted acids are deprotonated. As a result, pKa values may be different when measured in different solvents. For example, the pKa of water is 14.0 in pure water, but when dissolved in DMSO it is reported as 32.
What do pKa values depend on?
The strength of the acid (pKa) depends on the stability of the base. When the proton leaves the acid, it leaves behind its electrons. Those are super negative, and there is a big negative charge on the conjugate base. You know that if there is a concentrated negative charge, the base is not very stable.
What is pKa for weak base?
when the pH = pKa, the ratio of [base]/[acid] is 1 and log 1 = 0. In other words, the amount of the weak acid and the weak base are equal.
How do you know if a base will Deprotonate an acid?
To determine whether or not a given base will be sufficient to deprotonate a specific acid, compare the conjugate base with the original base. A conjugate base is formed when the acid is deprotonated by the base. In the image above, hydroxide acts as a base to deprotonate the carboxylic acid.
What is the pKa of THF?
pKa(THF)) 1.02((0.04)pKR(THF)+ 2.14((0.54) (5) Acid-Base Equilibria in Nonpolar Media J. Org. Chem, Vol. 71, No. 24, 2006 9065 Page 5 previously obtained for a host of bases and, thus, to obtain the absolute pKa values of these bases.
Does higher pKa mean stronger base?
Remember from general chemistry that pKa is equal to the negative log of the Ka. And the lower the pKa value the stronger the acid.
How does the value of pKa affect basicity?
The best way to quantify the basicity of an amine is to examine the pKa of its conjugate acid. The higher the pKa of the conjugate acid, the stronger the base.