Vibrational Spectra and Structure of Cyclopentane and its Isotopomers

Abstract

The infrared and Raman spectra of vapor, liquid, and solid state cyclopentane and its d(1), 1,1-d(2), 1,1,2,2,3,3-d(6), and d(10) isotopomers have been recorded and analyzed. The experimental work was complemented by ab initio and density functional theory (DFT) calculations. The computations confirm that the two conformational forms of cyclopentane are the twist (C(2)) and bent (C(s)) structures and that they differ very little in energy, less than about 10 cm(-1) (0.1 kJ/mol). The bending angle for the C(s) form is 41.5° and the dihedral angle of twisting is 43.2° for the C(2) form. A reliable and complete vibrational assignment for each of the isotopomers has been achieved for the first time, and these agree very well with the DFT (B3LYP/cc-pVTZ) computations. The ab initio CCSD/cc-pVTZ calculations predict a barrier to planarity of 1887 cm(-1), which is in excellent agreement with the experimental value of 1808 cm(-1).

Analytic calculation of ground state splitting in symmetric double well potential

“…For these objects detailed data on IR spectroscopy are available [57], [58], [59] that makes them to be good test objects for verifying the accuracy of various theoretical methods. Ring-puckering vibration (see [57], [58], [59], [60], [61], and refs.therein) along with ring-twisting, ring-flapping, wagging, torsion and inversion vibrations [57], [62], [63], [64] is an interesting interdisciplinary phenomenon for chemical physics, IR spectroscopy and physics of molecules. It was studied experimentally in details mainly in the laboratory of J. Laane and a lot of experimental data for numerous objects is available at present.…”

Exhaustive exploration of the conformational landscape of mono- and disubstituted five-membered rings by DFT and MP2 calculations

“…The low energy differences, despite being beyond the precision offered by these computational methods, were in good accordance with previous results obtained by Laane and co-workers. 22 The small energy differences and the low magnitude of the low frequency values for the stationary points clearly indicated a practically at potential energy surface around the pseudorotational cycle. However, it should be noted that aer adding the entropic and zero-point energies, the T shape became clearly favored (ca.…”

“…cisand trans-5-Methyl-2-hydroxy-THF (21)(22). The conformational analysis of furanoside-containing compounds has received considerable attention due to their relevance in different elds of chemistry and biology.…”

Theoretical calculations and vibrational potential energy surface of 4-silaspiro(3,3)heptane

“…The frequency calculation of the ring-puckering vibration was carried out using the B3LYP/cc-pVTZ basis set 10 and scaled with a factor of 0.985 based on previous work. [15][16][17][18][19][20][21][22] The Semichem AMPAC/AGUI 10.1 program 23 was used to visualize the vibrational motion and structure.…”