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Lewis lung carcinoma, and P-388 lymphocytic leukemia in the mouse and the Walker 256 intramuscular carcinosarcoma in the rat. Cytotoxicity and in vivo activity were assayed under the auspices of the Cancer Chemotherapy National Service Center, National Cancer Institute, by the procedures described in Cancer Chemother. Rep., 25, 1 (1962). Cytotoxicity was also assayed by differential agar diffusion by Professor D.

p-Methoxycinnamic acid (I) is nematogenic but cinnamic acid (11), although as a hydrogen-bonded dimer it has the necessary molecular anisotropy, is not. The crystal structures of the two compounds have been determined at room temperature, and this difference can be directly attributed to differences in molecular packing.Crystals of (11) are monoclinic, space group P2Jc with a = 5. 644(1), b = 18.011 (6). c = 9.019(3) 8, @ = 121.47(2)", and Z = 4. The structure w a s solved by direct methods and refined by least squares to R 0.059 for 899 independent reflections whose intensities were measured by counter diffractometry. Crystals of (I) are triclinic, space group P i with a = 8.336(2), b = 12.026(4). c = 4.842(2) 8, M = 81.80(3), p = 99.28(2), y = 11 1.90(3)".and Z = 2. The structure w a s solved by a Fourier-transform method, and refined by least squares to R 0.048 for 1 675 independent reflections.The molecular packing in crystals of ( 11) is zig-zag type with the long axes of the hydrogen-bonded dimers inclined at 45". Crystals of (I) have all molecules parallel in a three-dimensionally interlocked arrangement characteristic of nematogenic crystals.THERMOTROPISM of the trans-isomers of the #-n-alk-8.336(2), b = 12.026(4), c = 4.842(2) A, cc = 81.80(3), p = * Observed and calculated structure factors for (I) and (11) are listed in Supplementary Publication No. SUP 21503 (20 pp., 1 microfiche.