The crystal structures of three β-halolactic acids have been determined, namely, β-chlorolactic acid (systematic name: 3-chloro-2-hydroxypropanoic acid, C3H5ClO3) (I), β-bromolactic acid (systematic name: 3-bromo-2-hydroxypropanoic acid, C3H5BrO3) (II), and β-iodolactic acid (systematic name: 2-hydroxy-3-iodopropanoic acid, C3H5IO3) (III). The number of molecules in the asymmetric unit of each crystal structure (Z′) was found to be two for I and II, and one for III, making I and II isostructural and III unique. The difference between the molecules in the asymmetric units of I and II is due to the direction of the hydrogen bond of the alcohol group to a neighboring molecule. Molecular packing shows that each structure has alternating layers of intermolecular hydrogen bonding and halogen–halogen interactions. Hirshfeld surfaces and two-dimensional fingerprint plots were analyzed to further explore the intermolecular interactions of these structures. In I and II, energy minimization is achieved by lowering of the symmetry to adopt two independent molecular conformations in the asymmetric unit.
测定了三种β-半乳酸的晶体结构,即β-氯乳酸(系统名:3-氯-2-羟基丙酸,C3H5ClO3)(I)、β-溴乳酸(系统名:3-溴-2-羟基丙酸,C3H5BrO3)(II)和β-碘乳酸(系统名:2-羟基-3-碘丙酸,C3H5IO3)(III)。发现 I 和 II 晶体结构的不对称单元(Z′)中的分子数为两个,III 晶体结构的不对称单元中的分子数为一个,因此 I 和 II 晶体结构相同,III 晶体结构独特。I 和 II 不对称单元中分子的差异是由于醇基与邻近分子的氢键方向不同造成的。分子堆积显示,每种结构都有分子间氢键和卤素-卤素相互作用的交替层。通过分析 Hirshfeld 表面和二维指纹图谱,进一步探索了这些结构的分子间相互作用。在 I 和 II 中,能量最小化是通过降低对称性来实现的,即在不对称单元中采用两种独立的分子构象。