Oligomers. Relations between their computed free energies

Abstract

Free energies G(X)n of 12 1,ω‐dihydrooligomers (X)n (n, number of the monomeric units) have been determined by quantum calculations. We note that these values are correlated by (a) an excellent linear relationship: G(X)n = An – 761.86 ± 10 (kcal mol–1) (TPSS‐TPSS/6.311 + + G(dp)); (b) for two oligomers (X)n and (Y)n, the difference of weighted free energies—G(X)n/n – G(Y)n/n—is a constant irrespective of n which results from the difference of free energies of the substituent. Consequently, from the Gn values of 1,ω‐dihydrooligoethenes (in fact n‐alkanes), a determination of the free energies of a 1,ω‐dihydrooligomers (X)n is obtained with a good accuracy by the calculation of the G value of its substituent; (c) the corresponding increments G(X)n/n – G(X)(n–1)/(n–1) are equaled and led to a single power law: [Gn/n – G(n–1)/(n–1) = 1282/n2.156 (kcal mol–1), R = 0.9992] or a linear relationship: [Gn/n – G(n–1)/(n–1) = 756.73/n(n–1) + 0.0211 (kcal mol–1), R = 1]. Syndiotactic and isotactic 1,ω‐dihydrooligomers (X) are illustrated in the Electronic Supporting Information.