Enantiomers are stereoisomers that are non-superimposable mirror images of each other. They have the same molecular formula and the same connectivity of atoms but differ in the spatial arrangement of atoms in three-dimensional space. Due to their different spatial arrangements, enantiomers can exhibit different photochemical properties, particularly when they interact with chiral or polarized light.1. Interaction with plane-polarized light: Enantiomers rotate plane-polarized light in opposite directions. One enantiomer will rotate the light clockwise dextrorotatory, denoted as + or D , while the other enantiomer will rotate it counterclockwise levorotatory, denoted as - or L . This property is called optical activity, and it is a direct result of the different spatial arrangements of the enantiomers. For example, the enantiomers of limonene, a compound found in citrus fruits, have different optical rotations: + -limonene dextrorotatory and - -limonene levorotatory .2. Interaction with chiral molecules or environments: The photochemical properties of enantiomers can also differ when they interact with other chiral molecules or environments. For instance, chiral photosensitizers can selectively promote the photochemical reactions of one enantiomer over the other. This phenomenon is called asymmetric photochemistry and can be used for the synthesis of enantiomerically pure compounds. An example is the enantioselective photochemical [2+2] cycloaddition reaction of chiral alkenes, where a chiral photosensitizer selectively reacts with one enantiomer, leading to the formation of a specific cyclobutane product.3. Circular dichroism CD spectroscopy: Enantiomers exhibit different absorption of left and right circularly polarized light, which can be measured using circular dichroism spectroscopy. This difference in absorption, called circular dichroism, is a unique property of chiral molecules and can be used to study their structures, conformations, and interactions with other molecules. For example, the CD spectra of the enantiomers of a chiral drug can be used to determine their binding affinities to a chiral receptor.In summary, the photochemical properties of enantiomers can differ due to their distinct spatial arrangements, which affect their interactions with polarized light, chiral molecules, and chiral environments. These differences can be observed and utilized in various applications, such as asymmetric synthesis, chiral recognition, and the study of molecular interactions.