The direct observation of the stereospecificity during electrocyclic reactions by a structural dynamics study requires not only an unsymmetric substitution of the methylene groups, but also a conformer-pure sample. This is largely the case in αPh. As described above, the isopropyl substituent of αPh can be in either a quasi-equatorial or quasi-axial orientation. Additionally, in either of these two resulting conformers, it can exist in three different rotational orientations with respect to its bond with the six-membered ring, resulting in a total of six possible conformers (see structures in Fig. ). Comparison of the static PDF of αPh with simulations of all six conformers (see Fig. ) shows good agreement with all quasi-equatorial conformers and qualitative disagreement with the three quasi-axial conformers. Thus, the gas sample is dominated by equatorial conformers. The difference in the conformer PDFs is localized at 3.5 Å and 6 Å. Two out of three quasiaxial conformers show a shoulder at 3.5 Å, whereas the remaining conformers show a minimum.