Explain the discrepancy in reported product channels for the C3H3+–C2H4 reaction

Determine the origin of the discrepancy between the reaction-product channels reported for the C3H3+ + C2H4 reaction in earlier experiments and those predicted theoretically and independently observed in the present measurements.

Background

The paper examines the reaction of C3H3+ with C2H4 while distinguishing the linear propargyl cation from the cyclic cyclopropenyl cation. Earlier measurements produced mixtures of these isomers and reported product channels leading to C5H7+ and C5H5+, whereas the present isomer-selective measurements identify channels leading to C3H5+ and C5H5+. The total measured rate is consistent with theoretical calculations, but the individual product assignments remain discrepant.

The authors explicitly state that they cannot explain this discrepancy, leaving unresolved the mechanistic reason why the earlier experiment reported different reaction products from those obtained in the present measurements and predicted by the theoretical study.

References

Yet, our results confirm the discrepancy in the reported product channels highlighted by . Although we cannot provide an explanation for this discrepancy in the observed channels, we independently validate the theoretical results reported by .

— Gas-phase chemistry of $\mathrm{C}_3\mathrm{H}_3^+$: a key building block for carbon mass growth in space  (2610.11985 - Rossi et al., 8 Oct 2026) in Section 3.1, “Reactivity of C3H3+ with C2H4”