A new series of Schiff base esters, 4-(dimethylamino)benzylidene-4 0 -alkanoyloxyanilines containing even number of carbons at the end group of the molecules (C nÀ1 H 2nÀ1 COO, n = 6,8,10,12,14,16, 18) were synthesized. The present compounds were monotropic liquid crystals. It was also found that the end groups of the molecules had effect on the mesomorphic properties.

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The effects of supplementation with high-Se wheat bread on selenium (Se) concentrations, glutathione peroxidase (EC 1.11.1.9, GSHPx) activities and related enzymes in the prevention of lipid peroxidation were studied. Four New Zealand women were supplemented with 200 micrograms Se daily for 8-13 weeks followed by a post-dosing period of 9-12 weeks. GSHPx activities increased in whole blood, erythrocytes, plasma and platelets of all subjects but increases were considerably less than those of Se concentrations in whole blood, plasma and erythrocytes. During the post-dosing period Se concentrations and GSHPx activities fell to levels which were in most cases somewhat higher than baseline values. Glutathione-S-transferase activities in erythrocytes, plasma and platelets did not change during the study, nor did superoxide dismutase in erythrocytes and platelets, erythrocyte catalase or plasma alpha-tocopherol. Thus Se supplementation of healthy New Zealand subjects increased GSHPx activities but did not produce any adaptive changes in other components of the lipid peroxidation defense mechanisms.

Problem statement: Many studies have been conducted on the Schiff bases alkyl and alkyloxy possessing terminal halogen substituent. However, the thermotropic properties of Schiff bases ester (or alkanoyloxy) with chloro terminal group remained unstudied. Approach: Synthesis a series of new Schiff base ester possessing polar chloro group and investigate its mesomorphic properties. The title compounds were prepared via condensation and esterification reactions. The molecular structures were confirmed using spectroscopic techniques. All the members are differed by the length of alkanoyloxy chain, C_n-1H_2n-1COO, where n = 2-8, 10, 12, 14, 16 and 18. The mesomorphic properties were studied using differential scanning calorimetry, polarizing optical microscopy and temperature-dependent X-ray diffractometry. Results: Whilst short members (n = 2-5) were not mesogenic compounds, n-hexanoyloxy and n-heptanoyloxy derivatives exhibited monotropic SmA and SmB phases. Enantiotropic smectogenic A and monotropic smectogenic B were observed in n-octanoyloxy to n-hexadecanoyloxy derivatives. Highest member of the series, n-octadecanoyloxy derivatives exhibited monotropic SmA phase. Conclusion: The ester linkage and polar terminal group in the present series are essential for the formation of liquid crystal phase in Schiff bases