Molecular Structure of Piperazine as Studied by Gas Electron Diffraction

A study of piperazine by means of gas electron diffraction has given the following structural parameters (the rg distances and the angles based on the rα structure) with estimated limits of error: C–C=1.540±0.008 Å, C–N=1.467±0.004 Å, ∠C–C–N=110.4±0.8°, ∠C–N–C=109.0±0.8°, C–H=1.110±0.008 Å and ∠H–C–H=109·1±5°; the molecule takes a chair conformation. The C–C distance is nearly equal to that in cyclohexane, and the C–N–C angle is slightly smaller than the C–C–N angle. These angles agree with those predicted by an SCF-CNDO/2 method.