We investigated property-structure relations in a dichiral compound which exhibits an optically isotropic phase (IsoX). Slight modification of the molecular structure except the chain length suppressed the IsoX phase. A phase diagram between enantiomers suggests that chiral recognition induces the IsoX phase. A miscibility study between the dichiral compound (R, S) and a hydrazine derivative (BABH8) with a cubic phase was performed Both the IsoX phase and the cubic phase of BABH8 were suppressed. while the SmC* phase of (R, S) was miscible with the SmC phase of BABH8. The phase diagram reflects the competition between different intermolecular interactions. We discuss the novel chiral effect on mesophase formation.