Correct Symmetry Treatment for X + X Reactions Prevents Large Errors in Predicted Isotope Enrichment.

Confusion over how to account for symmetry numbers when reactants are identical can cause significant errors in isotopic studies. An extraneous factor of 2 in the reaction symmetry number, as proposed in the literature, violates reaction equilibrium and causes huge enrichment errors in isotopic analysis. In actuality, no extra symmetry factor is needed with identical reactants.