Three polymorphs (alpha, beta, and delta) of D-mannitol at 100 K.

In the monoclinic delta polymorph of D-mannitol, C(6)H(14)O(6), both the molecule and the packing have approximate twofold rotational symmetry. The P2(1) structure thus approximates space group C222(1), and the alpha' polymorph, previously reported in that space group, is almost certainly identical to the delta polymorph. However, torsion angles along the main backbone of the molecule deviate from twofold symmetry by as much as 7.4 (3) degrees and the hydrogen-bonding pattern does not conform to the higher symmetry. The alpha polymorph reported here is identical to the previously reported kappa polymorph, and the low-temperature structure of the beta polymorph agrees well with previously reported room-temperature determinations. The range of C-O bond lengths over the three polymorphs is 1.428 (2)-1.437 (4) A, and the range of C-C distances is 1.515 (4)-1.5406 (19) A. The delta polymorph has the highest density of the three, both at room temperature and at 100 K.