An Eco-Friendly Method for Saturated Hydrocarbon Chlorination: Exploring the Potential of First-Row Transition Metal...

The functionalization of saturated hydrocarbons in a controlled, efficient, and selective manner represents a significant challenge in modern chemistry due to the low reactivity of their C-H bonds. This study introduces a new chlorination method using trichloroisocyanuric acid (TCCA) as the halogenating agent and first-row transition metal salts as catalysts. The investigation utilized four different substrates (cyclohexane, n-hexane, cycloheptane, and norbornane) along with eight transition metal ions (V-(IV), Cr-(III), Mn-(II), Fe-(II), Ni-(II), Co-(II), Cu-(II), and Zn-(II)) as potential catalysts and further Li⁺. The reactions were conducted with a substrate:TCCA:catalyst ratio of 1000:333:1 at 25, 50, and 75 °C for 24 h. The highest yields were obtained with Cu-(ClO₄)₂.6H₂O at 75 °C: 42.1 ± 0.6% for chlorocyclohexane, 44.6 ± 0.7% for chlorocycloheptane, 42.1 ± 0.8% for exo-2-chloronorbornane, and 22.7 ± 0.6% for 2-chlorohexane. While higher temperatures (75 °C) enhance product yields, they also lower selectivity by promoting the formation of dichlorinated products. The reported system offers a safer and more efficient alternative for the selective chlorination of saturated hydrocarbons, achieving high yields and broad applicability.