title: Crystal structure of rac-3,9-bis-(2,6-di-fluoro-phen-yl)-2,4,8,10-tetra-oxa-spiro[5.5]undeca-ne.
abstract: The title compound, C19H16F4O4, was prepared by the condensation reaction of 2,6-di-fluoro-benzaldehyde and penta-erythritol. The whole mol-ecule is generated by twofold rotational symmetry. The two six-membered O-heterocycles adopt chair conformations through a shared spiro-carbon atom that is located on the crystallographic twofold rotation axis. In this conformation, the two aromatic rings are located at the equatorial positions of the O-heterocycles. The conformation of this doubly substituted tetra-oxa-spiro system is chiral. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds, forming layers parallel to (100). These layers are linked by C-H⋯F hydrogen bonds into a three-dimensional structure.
authors: Advanced Catalysis and Green Manufacturing Collaborative Innovation Center, Changzhou University, Changzhou 213164, Jiangsu, People's Republic of China.
authors: Liang
authors: L
authors: Chen
authors: Key Laboratory of Fine Chemical Engineering, Changzhou University, Changzhou, 213164, Jiangsu, People's Republic of China.
authors: Zhengyi
authors: Z
authors: Li
authors: Key Laboratory of Fine Chemical Engineering, Changzhou University, Changzhou, 213164, Jiangsu, People's Republic of China.
authors: Linlin
authors: L
authors: Jin
authors: Key Laboratory of Fine Chemical Engineering, Changzhou University, Changzhou, 213164, Jiangsu, People's Republic of China.
authors: Xiaoqiang
authors: X
authors: Sun
authors: Key Laboratory of Fine Chemical Engineering, Changzhou University, Changzhou, 213164, Jiangsu, People's Republic of China.
authors: Zhiming
authors: Z
authors: Wang
keywords: axial chirality; crystal structure; helical hydrogen-bonded chains; oxo-spiro­cyclic