Crystal structure of i -erythritol and its relationship to some derived d and l and racemic substances

Meso erythritol forms a tetragonal structure in which the molecules are centro-symmetric. Each α -hydroxyl group forms part of a tetragonal spiral of hydrogen bonds. These spirals alone are sufficient to link all the molecules of the crystal into a three-dimensional hydrogen-bonded complex. The β -hydroxyl groups of neighbouring molecules form closed circuits of four hydrogen bonds in a tetrahedron so flattened as to be almost a square. These closed circuits are also by themselves sufficient to link all molecules in the crystal into a three-dimensional complex. When some of the hydroxyl groups are replaced by fluorine atoms of approximately the same size, the main structure should be retained if sufficient hydrogen bonding is left. It is possible, therefore, to predict structures for meso , d , l and racemic forms of some of the fluoro-substituted derivatives. 2-deoxy-2-fluoro (±) erythritol has been examined and found to have the expected racemic structure. The possibility of forms transitional between dextro , racemic, and laevo , is discussed.