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Crystals of the monomer and polymer of the bis-ethylurethane of 5,7-dodecadiyne-l, 12-diol (1 a, ETCD, systematic name: 5,7-dodecadiynylene bis(N-ethylcarbamate) have been studied by X-ray powder and single-crystal photographic techniques. Lattice constants at 20 "C were obtained from both single-crystal and powder data and are in satisfactory agreement with a previous report. Lattice constants at 130-135 "C were obtained from powder data and reveal that the lattice expands in volume by 4% on heating from 20°C, in contrast to a previous report which indicated a volume contraction on heating. Rotation photographs of poly(ETCD) crystals before and after extraction of unpolymerized monomer with boiling methanol reveal that solvent extraction renders many reflections more diffuse. Weissenberg h0l-photographs of the polymer reveal sufficient disorder so as to preclude a high-precision structural determination. Rotation and Weissenberg photographs of monomeric ETCD at 20°C manifest the major reflections of the polymer.

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