Abstract
The reaction of stereoisomers of pentaneβ2, 4βdiol and heptaneβ2, 4, 6βtriol with formaldehyde was investigated as a model for the formalization reaction of poly(vinyl alcohol) in order to determine effect of the stereochemical configuration of the polyol molecules on the reaction. The isotactic (meso) diol portion reacted with formaldehyde to give cisβformal several times faster than did the syndiotactic (dl) diol portion to give transβformal at 30β80Β°C. In the reaction of heterotactic (mesoβdl) triol which provides both the isotactic and syndiotactic diol portions in a molecule, the proportion of transβformal in the total formal decreased as the reaction proceeded. This shows that the formation of cisβformal is also favored thermodynamically to a greater extent, and hence the intramolecular migration of transβformal to cisβformal did occur during the reaction. The rates of hydrolysis of formals of the diols were compared with those of the triols in order to see the effect of a hydroxyl group adjacent to the formal ring on the reaction. No appreciable rate difference was observed between the dimer and trimer models both in cisβ and transβ formals. Therefore it was deduced from these results that the increase of the rate of hydrolysis of poly(vinyl formal) with the increase of hydroxyl groups along the polymer chain is a characteristic of macromolecules that is not observed in the low molecular weight models.