A structural dynamics investigation into another substituted CHD derivative, α-terpinene (αTp), provides detailed insight into the mechanism of the electrocyclic ring-opening itself. αTp is an isomer of α-Phellandrene (αPh), where the isopropyl and methyl substituents are moved to the two ends of the conjugated π-system of the CHD ring (see e.g. Fig. ). Due to the symmetrical substitution of the methylene units, the structural signatures of the αTp ring-opening are much less sensitive to the stereo-specific character of the reaction than in αPh. However, the substituents provide "reporter" carbon-carbon distances in the ∆PDFs for the reformation dynamics of the conjugated π-system of αTp. Both the static PDF signatures of αTp and the time-dependent signatures of its ring-opening reaction are quite similar to CHD and αPh . After the completion of the ring-opening reaction (see e.g., the ∆PDF(r, 0.4ps) curve in Fig. ), similar signatures as in αPh are present, two negative signatures at 1.4 Å and 2.4 Å, and a positive signature at 3.5 Å.