Abstract
Reduction of bi-cyclo-[3.3.0]octane-3,7-dione yields a mixture of the endo-3,endo-7-diol and endo-3, exo-7-diol (C8H14O2) isomers (5 and 6). These form (5)2·(6) co-crystals in the monoclinic P21/n space group (with Z = 6, Z' = 1.5) rather than undergoing separation by means of fractional recrystallization or column chromatography. The mol-ecule of 5 occupies a general position, whereas the mol-ecule of 6 is disordered over two orientations across a centre of symmetry with occupancies of 0.463 (2) and 0.037 (2). Individual diol hy-droxy groups associate around a pseudo-threefold screw axis by means of hydrogen bonding. The second hy-droxy group of each diol behaves in a similar manner, generating a three-dimensional hydrogen-bonded network structure. This hydrogen-bond connectivity is identical to that present in three known helical tubuland diol-hydro-quinone co-crystals, and the new crystal structure is even more similar to two homologous aliphatic diol co-crystals.
Highlights
Reduction of bicyclo[3.3.0]octane-3,7-dione yields a mixture of the endo-3,endo7-diol and endo-3, exo-7-diol (C8H14O2) isomers (5 and 6)
Individual diol hydroxy groups associate around a pseudo-threefold screw axis by means of hydrogen bonding
The second hydroxy group of each diol behaves in a similar manner, generating a three-dimensional hydrogen-bonded network structure. This hydrogen-bond connectivity is identical to that present in three known helical tubuland diol– hydroquinone co-crystals, and the new crystal structure is even more similar to two homologous aliphatic diol co-crystals
Summary
Crystalline binary adducts (Herbstein, 2005) have been classified as clathrates, coordinatoclathrates, clathratocomplexes or complexes (Weber & Josel, 1983). If the two components are both solids of comparable size, the host–guest distinction vanishes The latter group of complexes are nowadays generally termed co-crystals (Aakeroy & Chopade, 2012). The first such material recognised as being a co-crystal was discovered in 1844 by Friedrich Wohler This was the 1:1 combination of p-benzoquinone 1 and hydroquinone 2, commonly known as quinhydrone 3 (Fig. 1) (Karagianni et al, 2018; Sakurai, 1968). These novel co-crystalline materials are generally discovered accidentally as a consequence of preparative organic work going wrong, in particular the very few instances where standard purification techniques fail. Quantitative descriptions of these conformational effects are summarized by the cyclopentane ring torsion angle values marked on Fig. 4
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
