Experimental Enthalpies of Formation and Strain Energies for the Caged C20H20 Pagodane and Dodecahedrane Frameworks

Hydrocarbon cages are key reference materials for the validation and parameterization of computationally cost-effective procedures such as density functional theory (DFT), semiempirical molecular orbital theory, and molecular mechanics. We obtain accurate total atomization energies (TAEs) and heats of formation (Δf H°298) for platonic and prismatic hydrocarbon cages by means of the Wn-F12 explicitly correlated thermochemical protocols. We consider the following kinetically stable (CH)n polycyclic hydrocarbon cages: (i) platonic hydrocarbons (tetrahedrane, cubane, and dodecahedrane), (ii) prismatic hydrocarbons (triprismane, cubane, and pentaprismane), and (iii) one truncated tetrahedrane (octahedrane). Our best theoretical heat of formation for cubane (144.8 kcal mol(-1)) suggests that the experimental value adopted by the NIST thermochemical database (142.7 ± 1.2 kcal mol(-1)) should be revised upwards by ∼2 kcal mol(-1). Our best heat of formation for dodecahedrane (20.2 kcal mol(-1)) suggests that the semiexperimental value (22.4 ± 1 kcal mol(-1)) should be revised downward by ∼2 kcal mol(-1). We use our benchmark Wn-F12 TAEs to evaluate the performance of a variety of computationally less demanding composite thermochemical procedures. These include the Gaussian-n (Gn) and the complete basis set (CBS) methods. The CBS-QB3 and CBS-APNO procedures show relatively poor performance with root-mean-squared deviations (RMSDs) of 4.2 and 2.5 kcal mol(-1), respectively. The best performers of the Gn procedures are G4 and G3(MP2)B3 (RMSD = 0.5 and 0.6 kcal mol(-1), respectively), while the worst performers are G3 and G4(MP2)-6X (RMSD = 2.1 and 2.9 kcal mol(-1), respectively). Isodesmic and even homodesmotic reactions involving these species are surprisingly challenging targets for DFT computations.

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“… Derived from the experimental Δ f H ° 298 values for dodecahedrane and pagodane derivatives (see Ref. for further details).…”

Section: Resultsmentioning

confidence: 99%

Heats of formation of platonic hydrocarbon cages by means of high‐level thermochemical procedures

2015

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“…[3, 4b] Thus, relative to parent 2, with the H···H interactions responsible for most of its strain energy (exp. 61.4 AE 1 kcal mol À1 [9] ), the thirty peripheral X···X interactions added up to a modest decrease in molecular strain for 3 but to an intimidating increase for 5 and 6. [10] In fact, from exploratory experimentation it was learnt that the installation of more than 10-12 chlorine or Abstract: "One-pot" substitution of the twenty hydrogen atoms in pentagonal dodecahedrane (C 20 H 20 ) by OH, F, Cl, and Br atoms is explored.…”

Section: Introductionmentioning

confidence: 99%

“…furan) or 1,3-dipolar reagents except the slim, sterically undemanding CH 2 N 2 . The absence of C 11 Cl 9 + / C 9 C 7 + ions in the MS spectra attested to a practically quantitative conversion, however, the flocky product was as insoluble as 20, hence not amenable to NMR analysis. IR bands were evidence for the formation of A C H T U N G T R E N N U N G D1-pyrazolines highest masses m/z 832-838 for C 20 Cl l6 ·2 CH 2 + ions (HR) showed, as for 20, the sequential loss of the sixteen Cl substituents; the series of doubly charged ions started with m/z 382 (C 20 Cl 12 ·2 CH 2 2 + ).…”

Section: Introductionmentioning

confidence: 99%

“…As exemplified with model oligobromides in Scheme 5 of the preceding paper, [7] could [Fe 2 (CO) 9 ] effect cis-b-eliminations of HBr and Br 2 in 31 to provide C 20 (hydro)fullerenes possibly protected in a defined way by [Fe(CO] 4 ] ligands, ultimately tenfold complexed C 20 Fe 10 (CO) x ? In explorative experiments, 31 reacted only very sluggishly when exposed to about two equivalents of reagent per substituent.…”

Section: Introductionmentioning

confidence: 99%

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Towards Perfunctionalized Dodecahedranes—En Route to C₂₀ Fullerene

Wahl

Weiler

Landenberger

et al. 2006

Chemistry A European J

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"One-pot" substitution of the twenty hydrogen atoms in pentagonal dodecahedrane (C(20)H(20)) by OH, F, Cl, and Br atoms is explored. Electrophilic insertion of oxygen atoms with DMDO and TFMDO as oxidizing reagents ended, far off the desired C(20)(OH)(20), in complex polyol mixtures (up to C(20)H(10)(OH)(10) decols, a trace of C(20)H(OH)(19)?). Perfluorination was successful in a NaF matrix but (nearly pure) C(20)F(20) could be secured only in very low yield. "Brute-force" photochlorination (heat, light, pressure, time) provided a mixture of hydrogen-free, barely soluble C(20)Cl(16) dienes in high yield and C(20)Cl(20) as a trace component. Upon electron-impact ionization of the C(20)Cl(16) material sequential loss of the chlorine atoms was the major fragmentation pathway furnishing, however, only minor amounts of chlorine-free C(20) (+) ions. "Brute-force" photobrominations delivered an extremely complex mixture of polybromides with C(20)HBr(13) trienes as the highest masses. The MS spectra exhibited exclusive loss of the Br substituents ending in rather intense singly, doubly, and triply charged C(20)H(4-0) (+(2+)(3+)) ions. The insoluble approximately C(20)HBr(13) fraction (C(20)Br(14) trienes as highest masses) obtained along a modified bromination protocol, ultimately allowed the neat mass selection of C(20) (-) ions. The C(20)Cl(16) dienes and C(20)H(0-3)Br(14-12) tri-/tetraenes, in spite of their very high olefinic pyramidalization, proved resistant to oxygen and dimerization (polymerization) but added CH(2)N(2) smoothly. Dehalogenation of the respective cycloaddition products through electron-impact ionization resulted in C(22-24)H(4-8) (+(2+)) ions possibly constituting bis-/tris-/tetrakis-methano-C(20) fullerenes or partly hydrogenated C(22), C(23), and C(24) cages.

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“…Early investigations on this kind of compound indicated that caged alkyl molecules possess high density, high strain, and some stability. 15, [22][23][24][25][26][27][28] From the 1960s onward, marked progress has been made in synthesized chemistry. [29][30][31] Many caged alkyls, such as cubane, 32 homocubane, 33 dodecahedrane, 34 and pentaprosmane, 35 were synthesized successfully.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Investigation on the Replacement of CH Groups by N Atoms in Caged Structure (CH)₈

Zhou

Wong

et al. 2006

J. Phys. Chem. A

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A molecular design was performed for the caged molecule (CH)8: the replacement of CH groups by N atoms to increase the content of N as well as reduce the content of H. A series of caged molecules were obtained: (CH)xN(8-x) (0 < or = n < or = 8). The studied aspects are as follows: (i) molecular geometries and electronic structures, (ii) the analysis of the electronic structure using natural bond orbital (NBO) and atoms in molecules (AIM), and (iii) some physicochemical properties of studied molecules, such as the dipole moments, IR vibrational spectra, NMR chemical shifts, heats of formation, and relative specific impulses, were provided. Our studies show that these molecules should be a kind of potential and novel energetic material. Our work provides some useful information for the experimental study of these molecules. The effect of the substitution of N atoms for CH groups on the properties of this kind of caged molecule is presented.

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Experimental Enthalpies of Formation and Strain Energies for the Caged C20H20 Pagodane and Dodecahedrane Frameworks

Cited by 44 publications

References 3 publications

Heats of formation of platonic hydrocarbon cages by means of high‐level thermochemical procedures

Heats of formation of platonic hydrocarbon cages by means of high‐level thermochemical procedures

Towards Perfunctionalized Dodecahedranes—En Route to C₂₀ Fullerene

Theoretical Investigation on the Replacement of CH Groups by N Atoms in Caged Structure (CH)₈

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Experimental Enthalpies of Formation and Strain Energies for the Caged C20H20 Pagodane and Dodecahedrane Frameworks

Cited by 44 publications

References 3 publications

Heats of formation of platonic hydrocarbon cages by means of high‐level thermochemical procedures

Heats of formation of platonic hydrocarbon cages by means of high‐level thermochemical procedures

Towards Perfunctionalized Dodecahedranes—En Route to C20 Fullerene

Theoretical Investigation on the Replacement of CH Groups by N Atoms in Caged Structure (CH)8

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Towards Perfunctionalized Dodecahedranes—En Route to C₂₀ Fullerene

Theoretical Investigation on the Replacement of CH Groups by N Atoms in Caged Structure (CH)₈