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Recently the relative energies, electronic properties, and atomic structures of disubstituted C 20H 18X 2 regioisomers (X = F, Cl, Br, or OH) at the level of B3LYP/6-31G(d,p) have been determined. The structures of dodecahedrane and its derivatives were studied at the level of molecular mechanics calculations, INDO calculations, and hybrid density functional B3LYP calculations. However, at present no 1,2-dimethyl ( ) and 1,7-dimethyl ( ) dodecahedranes have been reported, yet. Methyl dodecahedrane, 1,4-dimethyl ( ), 1,6-dimethyl ( ), 1,16-dimethyl ( ) dodecahedranes, and trimethyl dodecahedrane have subsequently been reported. The total synthesis of dodecahedrane was confirmed by the single-peak nature of the 1H and 13C NMR spectra, as well as the X-ray spectra. Moreover, Pólya’s theorem was applied to the enumeration of substituted dodecahedrane isomers. Since then, the synthesis of methyl-substituted dodecahedrane was also confirmed by X-ray analysis.
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Ī dodecahedrane derivative, namely, the symmetric 1,16-dimethyl derivative, has been synthesized experimentally. Using the PBE0/cc-pVDZ quantum chemical method, dipole moments, polarizabilities, the first hyperpolarizabilities for 1,2-diethynyldodecahedrane C 20H 18(CCH) 2 and diethynylmethanododecahedrane C 20H 18C(CCH) 2 including two neighboring ethynyl groups in vacuum and in tetrahydrofuran (THF) were reported. Exothermic characters of H-abstraction with the lower potential barrier indicate that the H-abstraction would dominate the reaction + C 20H 20 while endothermic characters with high potential barrier heights for two reaction pathways of C 20H 20 with indicate unfavorable thermodynamically and kinetically pathways for these reactions. ĭensity functional calculations of the reactions CX 3 radical + C 20H 20 (X = H, F, Cl, and Br) based on two pathways (H-displacement and H-abstraction from C 20H 20) showed that CH 3 radical prefers H-abstraction from C 20H 20 while F-displacement is favorable for the reaction of CF 3 radical with the fullerene. Also it was proposed that thiyl radical-promoted polycyclization to form dodecahedrane would be exergonic. By using density functional theory method, the structures and electronic states of alkyl radicals (R,, –4) added to C 20 fullerenes were investigated. Furthermore, this strain could be removed through reactions of C 20 that form sp 3 bonds.
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Therefore, the C 20 fullerene would be highly reactive owing to the fusion of strained 5-MRs.
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However, this rule cannot be satisfied for the smallest fullerene C 20, which contains twelve 5-membered rings (MRs) and zero 6-MRs. The geometry of fullerenes obeys the isolated-pentagon rule. The characteristics of the HOMO of derivatives show three patterns, implying that each derivative might undergo one of three entirely different sets of characteristic chemical reactions with electrophilic reagents.ĭedicated to Professor Roald Hoffmann on the occasion of his 80th birthday The HOMO was limitedly delocalized on the cage. The LUMO of each of the derivatives was equivalently delocalized over the void within the cage, implying that dimethyl derivatives are able to encapsulate atoms at the center of the cage. It would be disadvantaged thermodynamically for 1,2-dimethyl derivative that, in the experimental results, was not synthesized yet. The results suggest that 1,16-dimethyl dodecahedrane derivative is the most stable, whereas the 1,2-dimethyl derivative is the most unstable this implies that the distortion due to steric hindrance interactions would be a crucial effect on the relative energies of the dimethyl dodecahedranes. From the direct dimethyl substitution of the dodecahedrane cage, we could have five C 20H 18(CH 3) 2 derivatives which were geometrically optimized without constraints. The hybrid density functional (B3LYP/6-31G(d, p)) method was used to understand why 1,2-dimethyl dodecahedrane has not been reported yet.