Enantiomers are non-superimposable mirror images of each other, which means they have the same molecular formula and connectivity but differ in the spatial arrangement of their atoms. These differences in spatial arrangement can lead to different photochemical properties when enantiomers are exposed to light. The interaction between enantiomers and light is governed by the rules of photochemistry, which involve the absorption of light energy, the formation of excited states, and the subsequent chemical reactions that occur.The photochemical properties of enantiomers can differ due to their chiral nature, which can lead to different interactions with polarized light. When enantiomers absorb light, they can undergo various processes such as photoisomerization, photodissociation, and photoinduced electron transfer. These processes can result in different chemical reactions and products for each enantiomer.One example of enantiomers with different photochemical properties is the R and S enantiomers of limonene, a naturally occurring compound found in citrus fruits. The R enantiomer has a pleasant orange scent, while the S enantiomer has a pine-like scent. When exposed to light, the R enantiomer undergoes a photochemical reaction that forms a stable endoperoxide, while the S enantiomer does not. This difference in photochemical behavior can be attributed to the different spatial arrangements of the R and S enantiomers, which affect the way they interact with light.Another example is the enantiomers of the drug thalidomide, which was prescribed to pregnant women in the 1950s and 1960s to treat morning sickness. The R enantiomer of thalidomide is an effective anti-nausea drug, while the S enantiomer is teratogenic, causing severe birth defects. When exposed to light or in the human body, the enantiomers can interconvert through a photochemical reaction, making it difficult to separate the beneficial R enantiomer from the harmful S enantiomer. This led to the tragic consequences associated with thalidomide use.In synthetic settings, enantiomers can be selectively photochemically transformed using circularly polarized light CPL . CPL can induce enantioselective photochemical reactions by preferentially exciting one enantiomer over the other. This technique has been used to synthesize enantiomerically pure compounds, which are important in the pharmaceutical industry, as the different enantiomers of a drug can have different biological activities.In conclusion, the photochemical properties of enantiomers can differ due to their chiral nature, leading to different behaviors when exposed to light. These differences can have significant consequences in both natural and synthetic settings, affecting the properties and applications of the enantiomers. Understanding the photochemical behavior of enantiomers is essential for the development of new chiral compounds and the improvement of existing ones.