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Two new heterocyclic [3.3.3.01,5]-propellanoid compounds: 2,8-dioxatricyclo[3.3.3.01,5]undecane-3,7-dione and a related dimer

“…Small members of this class consequently have less void space and potentially higher crystal density than other comparable aliphatic compounds, as is the case for both (I) and (II), whose crystal densities are 1.413 and 1.382 Mg m À3 , respectively. A similar but even higher crystal density (1.452 Mg m À3 ) is seen in the transoid analog of (I) (Tsao et al, 2002). This density potential may not be realised in cases where the packing is dominated by hydrogen-bonding forces, which can actually prevent the closest possible (van der Waals) packing.…”

(2S,4aR,8aS)-6-Oxoperhydronaphthalene-2-acetic acid: `conglomerate' crystallization and catemeric hydrogen bonding in a bicyclic η-keto acid

“…For related literature describing enantiomeric segregation upon crystallization, see: Chen et al (2000); Tsao et al (2002); for the synthesis, see: Stork et al (1963).…”

“…Although bulk (I) was racemic (see Experimental), both molecules in the cell are of identical handedness, as reflected in the space group (P2 1 ), and the two H-bonding chains passing through the cell are screw-related. Such enantiomeric segregation in the crystallization of either racemates or conformational enantiomers, known as "conglomerate" crystallization, is uncommon but constitutes a few percent of known simple keto-acid cases (Chen et al, 2000;Tsao et al, 2002). In the H bonding, each carboxylic acid is linked to the ketone of a molecule translationally related in both the a & b directions, so that the chains advance at an angle to the cell axes.…”

Interplay of Thermochemistry and Structural Chemistry, the Journal (Volume 13, 2002) and the Discipline

“…In the next paper, Tsao et al [89] discussed a novel ring system that is simultaneously a [5.5.5] propellane and a dilactone. Surprisingly, there are almost no thermochemical data for any propellane except for reaction calorimetry for the simplest one, the triple cyclopropane [1.1.1] species [90], and the likewise cyclopropane-containing [3.2.1] species [91].…”