The enthalpies of combustion and formation of [2.2]-paracyclophane and triptycene

Abstract

The enthalpies of combustion, AH~, for crystalline [2.2]-paracyclophane (C~6H1~) and triptycene (C2oH~) have been measured by oxygen combustion calorimetry. The derived standard enthalpies of formation at 298.15 K in the crystalline state are (34.594-0.19) and (51.874-0.20) kcalth mol-1. The strain present in these molecular systems is discussed.

Estimation of the Barrier to Rotation of Benzene in the (η6-C6H6)2Cr Crystal via Topological Analysis of the Electron Density Distribution Function

“…According to the experimental data, the total energy of the H···H contacts per independent molecule in the crystal (68.6 kJ mol -1 ) is close to that obtained by the PW-PBE calculation of the crystal (71.1 kJ mol -1 ) . In the case of [2.2]paracyclophane, the total energy of all H···H and H···C contacts per molecule in the crystal according to XRD (91.8 kJ mol -1 ), is close to the E lattice obtained by the PW-HCTH/120 calculation (95.96 kJ mol -1 ) 2 and to the experimental value of (96.2 ± 4.2 kJ mol -1 ) …”

π‐Orbital Interactions in Möbius‐Type Molecules as Studied by Photoelectron Spectroscopy

“…Concerning ground state properties, 1 exhibits an exceptionally large heat of hydrogenation for the first double bond which has recently been shown conclusively to result from through-space nln-repulsions [8]. Our analysis indicates that 4 ought to behave qualitatively the same as 1, which agrees with the nonclassical strain deduced from its heat of formation [9].…”

Nonconjugated Hydrocarbons as Rigid‐Linear Motifs: Isosteres for Material Sciences and Bioorganic and Medicinal Chemistry

“…Strain energy per CÀCbond [kcalmol À1 ] cyclopropane (C 3 H 6 )5 05.8 [106] 12.7 [106] 27.7 [15] 9.1 cyclobutane (C 4 H 8 )656.0 [92] 6.8 [107] 26.3 [15] 6.6 cyclohexane (C 6 H 12 )9 43.8 [108] 29.8 [108] 0.4 [15] 0.1 BCP (C 5 H 8 )N/D [a] 51 (calcd) [109] 68.0 [15] 11.3 cubane (C 8 H 8 )1155.2 [67] 142.7 [67] 161.5 [68] 13.5 BCO (C 8 H 14 )1195.5 [110] 23.6 [110] 7.4 0.8 triptycene 2409.1 [111] 76.8 [111] 7.0 [111] 0.8 energy of cubane is about six times the amount of cyclobutane, which represents the sum of the six "cyclobutane faces of the cube".B ut compared to the ring strain per carboncarbon bond, cubane has double the amount of cyclobutane. The deviation is even higherwhen the strain energy is calculated per number of carbon atoms (cubane % 20.2 kcal vs. butane % 6.6 kcal).…”