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<p>The formation of C<sub>4</sub>H<sub>3</sub>N isomers (1-cyano-cyclopropene, propargyl cyanide, cyanoallene, cyanopropyne, and their isonitrile analogs) via radical association and hydrogen migration reactions between propargyl (CH<sub>2</sub>CCH) and cyano (CN) radicals was investigated using quantum chemical calculations at the ωB97XD/aug-cc-pVQZ level, with CCSD (T)/aug-cc-pVQZ single-point energies for improved accuracy. These radicals, abundant in the interstellar medium (ISM), are key precursors to nitrogen-containing molecules relevant to prebiotic chemistry. The Calculated Potential energy surfaces (PES) reveal barrierless, exothermic pathways for nitrile and isonitrile formation, though their ultimate efficiency in low-temperature environments like TMC-1 is constrained by the competition between redissociation and radiative stabilization. Our kinetic analysis demonstrates that gas-phase radiative association is inefficient, strongly suggesting that the interstellar abundances of these complex species are primarily driven by alternative pathways, such as dust-grain surface chemistry or alternative abstraction routes. Hydrogen migration pathways possess high barriers and are kinetically inhibited in quiescent clouds. Vibrational frequencies and infrared (IR) spectra were calculated to validate the computational methods and aid in the future molecular identification of less studied cyclic and isonitrile reaction products, while electronic transitions were computed using CAM-B3LYP. These findings provide foundational thermochemical data for these new pathways and enhance our understanding of nitrile and isonitrile chemistry in star-forming regions.</p>

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Computational investigation of interstellar C4H3N isomers formation via propargyl and cyano radical association

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月2日

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  • Parmanand Pandey,
  • Pravi Mishra,
  • Rachana Singh,
  • Manisha Yadav,
  • Shivani,
  • Aftab Ahamad,
  • Alka Misra,
  • Poonam Tandon,
  • Amritanshu Shukla

摘要

The formation of C4H3N isomers (1-cyano-cyclopropene, propargyl cyanide, cyanoallene, cyanopropyne, and their isonitrile analogs) via radical association and hydrogen migration reactions between propargyl (CH2CCH) and cyano (CN) radicals was investigated using quantum chemical calculations at the ωB97XD/aug-cc-pVQZ level, with CCSD (T)/aug-cc-pVQZ single-point energies for improved accuracy. These radicals, abundant in the interstellar medium (ISM), are key precursors to nitrogen-containing molecules relevant to prebiotic chemistry. The Calculated Potential energy surfaces (PES) reveal barrierless, exothermic pathways for nitrile and isonitrile formation, though their ultimate efficiency in low-temperature environments like TMC-1 is constrained by the competition between redissociation and radiative stabilization. Our kinetic analysis demonstrates that gas-phase radiative association is inefficient, strongly suggesting that the interstellar abundances of these complex species are primarily driven by alternative pathways, such as dust-grain surface chemistry or alternative abstraction routes. Hydrogen migration pathways possess high barriers and are kinetically inhibited in quiescent clouds. Vibrational frequencies and infrared (IR) spectra were calculated to validate the computational methods and aid in the future molecular identification of less studied cyclic and isonitrile reaction products, while electronic transitions were computed using CAM-B3LYP. These findings provide foundational thermochemical data for these new pathways and enhance our understanding of nitrile and isonitrile chemistry in star-forming regions.