A number of aryl semicarbazones had been shown previously to possess s
ignificant anticonvulsant properties. The principal objective of the p
resent investigation was to determine the importance of the primary am
ino group in this series of compounds by replacing it with other subst
ituents. The results indicate that the amino group was not essential f
or anticonvulsant activity. However its replacement by an aryl ring ge
nerally abolished activity while a terminal phenylamino function was b
etter tolerated. Thus both the size of the group and its hydrogen bond
ing capabilities appear to influence bioactivity. Alteration of the ox
ygen atom of the semicarbazones by isosteres did not enhance anticonvu
lsant properties.