Strain energies in cyclic oxygen On, n = 3-8

ABSTRACT:The conventional strain energies for all four isomers of oxadiazetidine are determined within the isodesmic, homodesmotic, and hyperhomodesmotic models. Optimum equilibrium geometries, harmonic vibrational frequencies, and corresponding electronic energies are computed for all pertinent molecular systems using self-consistent field theory, second-order perturbation theory, and density functional theory (DFT) and employing two basis sets of triple-zeta valence quality: 6-311G(d,p) and 6-311ϩG(2df,2pd). The DFT functional employed is Becke's three-parameter hybrid functional using the Lee, Yang, and Paar correlation functional. Single-point fourth-order perturbation theory and coupled-cluster theory restricted to single and double excitations [CCSD(T)] calculations employing the larger basis set also are computed, at both the second-order Møller-Plesset (MP2)/6-311G(d,p) and the MP2/6-311ϩG(2df,2pd) optimized geometries, to determine the effect of higher-order correlation effects on strain energy computation and to gauge the effect of geometry on these effects. Using the same models and methods, the conventional strain energies for both isomers of oxazetidine also are computed, to determine the effect on the strain energy of replacing a nitrogen with a carbon in the ring.

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“…All three of these models may be grouped together within the s-homodesmotic model of Zhao and Gimarc [28] shown in Eqs. (1)(2)(3).…”

Section: Computational Detailsmentioning

confidence: 99%

“…In recent years studies of ring strain have included larger hydrocarbons [23][24][25][26] and other homocyclic systems [27][28][29][30][31][32]. Relatively few studies, however, have dealt with the computation of strain energy in heterocyclic systems [10,[33][34][35][36].…”

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confidence: 99%

Conventional strain energy in the oxadiazetidines

Benton

Magers

2004

Int J of Quantum Chemistry

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“…30 Theoretical calculations predicted that the parent dioxirane (2, R = H) is 24-29 kcal mol Ϫ 1 more stable than the parent carbonyl oxide (1, R = H), and that both forms can exist as distinct species divided by the activation energy as high as 18-24 kcal mol Ϫ 1 . 31 Such a preference for the cyclic form is in contrast to the case of ozone (X = O), for which the cyclic isomer was estimated to be 28-29 kcal mol Ϫ 1 higher in energy 32 and no experimental evidence for the cyclization was given for the cyclization under thermal or photolytic conditions. 33 Thus, the relative stability of open X-O-O species versus its cyclic form seems to decrease on going to more electropositive X, since the large difference in electronegativities between X and terminal O results in a highly polarized structure (X + -O-O Ϫ ) where the charges are rather localized and hence the delocalization energy of -electrons is minimized.…”

Section: Isomerization To Dioxiranesmentioning

confidence: 93%

Novel aspects of carbonyl oxide chemistry

Ishiguro

Nojima

Sawaki

1997

J. Phys. Org. Chem.

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The structural and chemical properties of 1,3-dipolar peroxidic species (X-O-O) such as ozone (X = O) and carbonyl oxides (X = R 2 C) depend significantly on the nature of X. Although cyclic O 3 is thermodynamically unstable, dioxiranes, cyclic isomers of carbonyl oxides, are isolable and have been fully characterized. In contrast to the well known electrophilic nature of ozone, carbonyl oxides usually act as a nucleophilic oxygen transfer agent, but their reactivity could be altered by substituents. It is expected that the chemistry of R 2 C-O 2 species will provide a good starting point for a better understanding of dioxygen complexes (X-O 2 ) with various Xs. Interesting aspects of carbonyl oxide chemistry are discussed, including methods of generation, cyclization to dioxiranes and the nature of their oxygen transfer activities.

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“…Various reactions have been suggested in the literature ranging from isogyric to isodesmic to homodesmotic forms [37,38]. Among them, the relatively accurate is homodesmotic schemes [39][40][41][42][43] in which not only the number of various bonds is conserved but also the valence environment around each atom is preserved to raise the advantage of canceling of systematic errors [44].…”

Section: Computational Detailsmentioning

confidence: 99%

“…DFT methods have been proved accurate for computing HOF through appropriate reactions [21][22][23][24][25][62][63][64][65]. In the present work, we calculated the HOFs of S1 and S2 by reaction (1) and (2) Table 4 collects the total energies (E 0 ) and SEs of the species involved in the reactions.…”

Section: Strain Energy and Heat Of Formationmentioning

confidence: 99%