Search results
Results from the WOW.Com Content Network
Because the relationship pK b = pK w − pK a holds only in aqueous solutions (though analogous relationships apply for other amphoteric solvents), subdisciplines of chemistry like organic chemistry that usually deal with nonaqueous solutions generally do not use pK b as a measure of basicity.
The higher the proton affinity, the stronger the base and the weaker the conjugate acid in the gas phase.The (reportedly) strongest known base is the ortho-diethynylbenzene dianion (E pa = 1843 kJ/mol), [3] followed by the methanide anion (E pa = 1743 kJ/mol) and the hydride ion (E pa = 1675 kJ/mol), [4] making methane the weakest proton acid [5] in the gas phase, followed by dihydrogen.
The term acidity function is also used for measurements made on basic systems, and the term basicity function is uncommon. Hammett-type acidity functions are defined in terms of a buffered medium containing a weak base B and its conjugate acid BH + :
Its conjugate base is the acetate ion with K b = 10 −14 /K a = 5.7 x 10 −10 (from the relationship K a × K b = 10 −14), which certainly does not correspond to a strong base. The conjugate of a weak acid is often a weak base and vice versa.
For comparison with the pKa's for phosphoric acid are 2.14, 7.20, and 12.37. At physiological pH's, pyrophosphate exists as a mixture of doubly and singly protonated forms. When molten, pyrophosphoric acid rapidly converts to an equilibrium mixture of phosphoric acid, pyrophosphoric acid and polyphosphoric acids.
Field effects can therefore tune the acidity or basicity of bonds within their fields by donating or withdrawing charge density. [5] With respect to acidity, a common trend to note is that, inductively, an electron-withdrawing substituent in the vicinity of an acidic proton will lower the pKa (i.e. increase the acidity) and, correspondingly, an ...
Acid-base discrimination windows of common solvents [1]. Leveling effect or solvent leveling refers to the effect of solvent on the properties of acids and bases. The strength of a strong acid is limited ("leveled") by the basicity of the solvent.
Brønsted and Pederson first discovered the relationship between basicity, with respect to protons, and nucleophilicity in 1924: [3] where = + where k b is the rate constant for nitramide decomposition by a base (B) and β N is a parameter of the equation.