Prepenultimate

Inversion at each additional step by the attack of the monomer's electron pair insures that when carbon 3 becomes part of the prepenultimate unit and carbon 1 becomes part of the penultimate unit they will have the same configurations.

The prepenultimate row reports overall statistics for ES engagements, which may be compared with CG engagements in the first row. The penultimate row provides chi-square tests of the difference between ES and CG engagements. The last row provides summary statistics for the entire sample, comprising both CG and ES engagements.