Theoretical Study of the Diels−Alder Reactions between Singlet (¹Δ_g) Oxygen and Acenes

Abstract

The G3(MP2) method has been employed to study the 1,4-addition reactions between singlet oxygen and five acenes, including benzene, naphthalene, anthrecene, tetracene, and pentacene. In all, nine pathways between O(2) and the five acenes have been investigated. Our calculated results indicate that all nine pathways are concerted and exothermic and that the most reactive sites on the acenes are the center ring's meso-carbons. In addition, reactivity increases along the series benzene < naphthalene < anthrecene < tetracene < pentacene. This trend is identical to that of aromaticity for the five acenes. A correlation between reactivity and aromaticity is briefly rationalized with natural bond orbital (NBO) analysis and frontier molecular orbital (FMO) analysis. Furthermore, some experimental kinetics data from the literature supporting the calculated results are cited.

Theoretical Study of the Oxidation of Histidine by Singlet Oxygen

“…Energy of singlet oxygen: A proper theoretical description within a single determinant framework of the delta state of singlet oxygen requires a complex wavefunction. To circumvent this theoretical difficulty, we used a previously proposed procedure [26] that involves consistently estimating the energy of 1 O 2 by adding the experimentally determined singlet-triplet gap energy, 22.5 kcal mol À1 , [27] to the calculated values of 3 O 2 . The DFT energy of 3 O 2 was obtained by using the unrestricted B3LYP method whereas the restricted open-shell coupled cluster method implemented in MOLPRO was used to compute its CCSD(T) energy.…”

Overview of Theoretical and Computational Methods Applied to the Oxygen‐Organic Molecule Photosystem

“…the initial reaction intermediate resembles a biradical, but this biradical closes to the endoperoxide without a barrier) (135). The reaction of singlet oxygen with aromatic hydrocarbons, however, is predicted to occur by a concerted mechanism (134,136).…”

9‐Boraanthracene Derivatives Stabilized by N‐Heterocyclic Carbenes

“…[22] Even then, reaction times are on the order of hours, not the minutes observed for conversion of compounds 3 to 4 upon treatment with oxygen. Higher acenes, such as tetracene and pentacene, are thought to react much more readily with triplet oxygen owing to a greater tendency towards biradical ground-state structures; [1,23,25] these results suggest that 9-boraanthracene derivatives behave more like higher acenes in this regard. While it has been suggested computationally that a thermal reaction pathway between anthracene and 3 O 2 is competitive with that involving 1 O 2 , [23] only in the strained helianthracene molecule IV has thermal reaction with 3 O 2 been observed experimentally, [24] and this reaction is exceedingly slow.…”