Laane has utilized high level computations to examine the high resolution IR and raman spectra of cyclopentane and some deuterated isomers.1 What is particularly of interest here is the excellent agreement between the experiment and computations. The barrier for planarity is estimated from experiment to be 1808 cm-1 and CCSD/cc-pVTZ predicts a value of 1887 cm-1 – excellent agreement. The B3LYP/cc-pVTZ computed frequencies for the C2 and Ci conformations were scaled by 0.985 for frequencies less than 1450 cm-1, 0.975 for frequencies between 1450 and 200 cm-1 and by 0.961 for frequencies above 2000 cm-1. These frequencies are very similar to one another. In comparison of these averaged frequencies with the experimental frequencies the root mean squared error is only 8.8 cm-1! As stressed by these authors, computational is important partner with experiment in characterizing spectra.
(1) Ocola, E. J.; Bauman, L. E.; Laane, J., "Vibrational Spectra and Structure of Cyclopentane and its Isotopomers," J. Phys. Chem. A, 2011, 115, 6531–6542, DOI: 10.1021/jp2032934.
Cyclopentane: InChI=1/C5H10/c1-2-4-5-3-1/h1-5H2 InChIKey=RGSFGYAAUTVSQA-UHFFFAOYAL