The C₃H₃O Potential Surface: Reactions of c-C₃H₂with OH and its Interstellar Implications

Formation mechanisms for the novel astromolecule hydroxy cyclopropenylidene and the previously-detected cyclopropenone are reported, representing new ways to create the elusive carbon-oxygen linkage in space. The recent detection of ethynyl cyclopropenylidene in the cold molecular cloud TMC-1 makes way for the study of other functionalized cyclopropenylidenes, but may also be linked to a distant relative, cyclopropenone, in Sagittarius B2. High-accuracy CCSD(T)-F12b/cc-pVTZ-F12 calculations are used to optimize structures and generate harmonic frequencies for minima along the reaction pathway. Ground and excited-state potential energy scans are used to connect structures along the pathway, and molecular orbital analyses help to explain unusual structure formation and incentives for dissociation. All products are found to have multiple kinetically-barrierless paths to reaction. The antiperiplanar isomer of hydroxy cyclopropenylidene is found to have far greater opportunity for product formation than its synperiplanar rotamer. However, cyclopropenone is found to be far lower in energy than either isomer of hydroxy cyclopropenylidene, resulting in a strongly competing pathway for functionalized cyclopropenylidene formation. The branching ratio of this reaction will be largely dictated by impact of well depth on association and dissociation rates.