The role of hydrogen bonding in the incommensurate modulation of myo-inositol camphor ketal

The incommensurate modulation of myo-inositol-2,3-d-camphor ketal is due to a complex diperiodic hydrogen-bonding network.

Upon filtration and concentration under reduced pressure, a pale yellow liquid was obtained (19.4 g, 85% wt purity), containing the product, toluene (10 mol%) and starting material (10 mol%) and used as-is.

Reactive crystallization and isolation:
Chloroform (75.5 mL), methanol (4.8 mL), water (1.51 mL) and p-toluene sulfonic acid (16.8 mg) was added and the mixture was stirred for 17 h during which time a colorless solid precipitated. The solid was collected by filtration and washed with chloroform (2 × 60 mL) and dried in vacuo to yield the crude product as a colorless solid (6.31 g). 13 C-NMR showed the desired diastereomer to be the major species out of three detected compounds.

S2. Modulation of the molecule
The C-C and C-O distances are given as t-plots in Fig. S3. As expected, the C-C distances in the strained bornane moiety feature a greater spread with the shortest and longest bond both involving the quaternary C12 atom. S3. Evolution of the q-vector with temperature Table S1 gives the temperature dependence of the σ 2 -component of the q-vector as well as the absolute period of the modulation weave in [010] direction in numerical form.

S4. Thermal analysis
In search of an order/disorder phase transition to a disordered non-modulated phase, a combined DSC/TGA analysis of microcrystalline 1 powder was performed using a NETZSCH STA 449 F1 Jupiter simultaneous thermal analyzer in the 300-525 K temperature range under Ar atmosphere in an Al crucible with pierced lid.
A finely powdered sample of 1, which was single-phase according to X-ray powder diffraction, was subjected to DSC measurements in the 300 to 525 K temperature range (Fig. S4). The endothermic melting effect has an onset of 505 K, which corresponds precisely to the melting point determined using an OptiMelt melting point apparatus.
It is overlain by a broad endothermic effect starting at ca. 480 K, which we attribute to decomposition, since it is accompanied by a mass loss of ca. 1.7 %. There are no signs of other effects of either the first or the second order and thus no clear evidence of a disordering of the structure up to its melting point (with decomposition). On cooling, recrystallization occurs at a strongly depressed temperature of ca. 435 K, which is probably due to partial decomposition and a general tendency of sugars and sugar-like polyols to form supercooled liquids.