How to circumvent plastic phases: the single crystal X-ray analysis of norbornadiene

Preparation and Properties of Centrally Bridgehead‐Substituted Hexacyclo[4.4.0.02,1.03,5.04,8.07,9]decanes (“Diademanes”) and Related (CH)10Hydrocarbons

“…Preparation of C6-substituted diademanes: The only method of preparing diademane 1 a is by long-term irradiation of pentacyclo[4.4.0.0 2,4 .0 3,8 .0 5,7 ]dec-9-ene (snoutene) 9 a (R H) at low temperature.…”

“…In an effort to investigate the thermodynamic and structural driving forces for the rearrangements within the (CH) 10 hydrocarbon family with a broader scope, [6a, 7] the recently elaborated in situ crystallization technique for compounds that form plastic phases [8] was applied and gave good results for basketene. However, X-ray diffraction results for a single crystal of diademane 1 a grown by careful heating with the IR laser (only to about 60 8C, in order to avoid rearrangement to 3 a) showed a tetrahedrally disordered structure in which the apical C atom of the diademane structure is positioned in each three-membered ring.…”

“…[8] However, according to DSC measurements, they were completely disordered and could not be used to derive structural details of the molecule. [7] Nevertheless, ab initio calculations performed for snoutene 9 a did not show any drastic deviations from the normal values of bond lengths and angles, except for a slight lengthening of four cyclopropane bonds (1.517 versus 1.504 ä for the other two).…”

“…Among the members of the (CH) 10 hydrocarbon family, which-like other (CH) n hydrocarbon families-is known for its multiple photochemical and thermal rearrangements, [1,2] the one nick-named ™diademane∫ (hexacyclo-[4.4.0.0 2,10 .0 3,5 .0 4,8 .0 7,9 ]decane, 1 a [3] ) draws the eye because of its molecular shape, resembling that of a closed crown. Diademane 1 a is also remarkable because of its facile thermal rearrangement leading to triquinacene 3 a, in which the C 3v symmetry of the precursor is retained.…”

The Melting Point Alternation in the Short-Chainn-Alkanes: Single-Crystal X-Ray Analyses of Propane at 30 K and ofn-Butane ton-Nonane at 90 K

“…Such a strategy has also been applied for circumventing plastic phases. [15] Similar experiments to crystallize n-decane, however, were not successful thus far. The disorder in the high temperature phase of n-butane could not be resolved during the structure refinement and led to high anisotropic displacement parameters, high residual electron densities, too short C À C bond distances, and a relatively high R value.…”