The polymerization of propylene oxide catalyzed by solid anhydrous KOH is shown to have essentially the same mechanism a s the well-known horriogeneous base-catalyzed polymerizations. The reaction is not surfacecatalyzed and the role of solid KOH is to convert hydroxylic groups almost quantitatively to alkoxide groups. Unsaturated end groups are shown to conie from rearrangement of propylene oxide to allyl alcohol, which initiates new polymer chains. Allyl ethers thus formed are converted t o &-propenyl ethers a t rates dependent upon their molecular weights. A kinetic analysis shows that the proposed reaction sequence accounts for all the characteristics of the polymerization including reaction rates, induction period, average molecular weight, and molecular weight distribution, and the arnount and type of unsaturation in the polymer. (51 C. C Price, lecture delivered a t Sorthwestern University, Dec. 8, 1959 I6J I ) M. Simons and J. J. I'erbanc, J. Polymer Sci , 44, 803 (1!>60) ( 7 ) G. Gee, Chem I n d . fI.ondonj, 678 (19.59).

van Remoortere, et al.148 mm, 20X reduction, negatives) containing all of the supplementary material for the papers in this issue may be obtained from the Journals

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A stereocontrolled synthetic route to optically pure (-)-(S)-ipsenol (l), the pheromone of Pityokteines curuidens and various other bark-beetle species is described. Key step of the synthesis is an enantioselective aldol reaction using a chiral titanium-cabrohydrate complex (Scheme I). The carboxylate function of the optically pure B-hydroxy acid 5 thus obtained in mol quantities is then elaborated to the dime moiety by standard methodology (Scheme 2).Various species of bark beetles are important pests to coniferous forests throughout the world. Among these are beetles of the genus Ips. In 1965 Silverstein et al.