The Reaction between Cyclopropane and the CN Radical: A Theoretical Study of Potential Astrochemical Relevance

Abstract

This study presents a comprehensive theoretical investigation of the kinetics and mechanism of the c-C₃H₆ + CN reaction over the 10–740 K temperature range. The results show that hydrogen abstraction by the CN radical, yielding the cyclopropyl radical and hydrogen cyanide, is exothermic and proceeds through a submerged barrier, suggesting a favorable reaction pathway under interstellar conditions. The rate constants calculated at the CCSD(T)/cc-pVTZ//CCSD/cc-pVDZ level using the VTST method between 297 and 740 K agree very well with previously reported experimental data and fit the expression k^VTST = 2.93 × 10^–16 T^1.76 exp(0.05 kcal mol^–1/RT) cm³ molecule^–1 s^–1. Between 10 and 297 K, the temperature dependence k = 1.3 × 10^–11 (T/300)^−2.2 exp(−39.0/T) cm³ molecule^–1 s^–1 is obtained by combining the room temperature rate constant with two values calculated from the capture model. Additionally, anharmonic rovibrational data for cyanocyclopropane are computed and compared with the available experimental measurements. According to these findings, cyanocyclopropane emerges as a promising target for future astrochemical detection, most likely through radioastronomy due to its large dipole moment of 4.25 D.