The potential of mean torque governing the orientational ordering of prochiral solutes in the two nematic phases (N and N_X) formed by certain classes of symmetric achiral bimesogens is formulated and used for the analysis of existing NMR measurements on solutes of various symmetries dissolved in the two phases. Three distinct attributes of the solvent phase, namely polarity of the orientational ordering, chirality of the constituent molecules, and spatial modulation of the local director, are identified as underlying three possible mechanisms for the generation of chiral asymmetry in the low temperature nematic phase (N_X). The role and quantitative contribution of each mechanism to enantiotopic discrimination in the N_X phase are presented and compared with the case of the conventional chiral nematic phase (N*). It is found that polar ordering is essential for the appearance of enantiotopic discrimination in small rigid solutes dissolved in the N_X phase and that such discrimination is restricted to solutes belonging to the point group symmetries C_s and C_2v.

中文翻译：

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刚体手性溶质在双生源的N _X相中的极性分子有序性和NMR光谱中的对映体区分

公式化了控制某些非对称非手性双生源形成的两个向列相（N和N _X）中前手性溶质的取向次序的平均转矩势，并将其用于分析现有的NMR测量，分析了各种对称性的非对称手性溶质。两个阶段。溶剂相的三个不同属性，即取向顺序的极性，组成分子的手性和局部指向矢的空间调节，被确定为在低温向列相中产生手性不对称性的三种可能机制（N _X）。N _X中每种机制对映体歧视的作用和定量贡献提出并与常规手性向列相（N *）的情况进行比较。已经发现，极性排序对于在N _X相中溶解的小的刚性溶质中对映体鉴别的出现是必不可少的，并且这种鉴别仅限于属于点群对称性C _s和C _{2 v的}溶质。