New applications of recurrent relations: precalculation of pKa values of substituted alkanecarboxylic acids

摘要

The series of substituted alkanecarboxylic acids including insertion homologues of ω-substituted acids X(CH2)nCO2H (n ≥ 1) and isomers that differ in the position of substituents X in the alkyl fragments, k-X(CnH2n)CO2H (n = const ≥ 1, 1 ≤ k ≤ n + 1) is the sub-group most poorly characterized by their acidity constants, pKa, comparing with the acids of the other sub-groups. When the experimental data for such compounds are unavailable, the precalculated estimates should be taken into consideration. The pKa values for such acids can be calculated using the single first-order recurrent relation, pKa(n+1) = apKa(n) + b, using pKa values of other (usually the simpler and, consequently, better characterized) homologues and/or isomers of the same series. This algorithm results from the unique mathematical properties of recurrent relations in chemistry.