<i>Cis/Trans</i> Energetics in Epoxide, Thiirane, Aziridine and Phosphirane Containing Cyclopentanols: Effects of Intramolecular OH⋯O, S, N and P Contacts

• Main Authors: Ben E. Smith, Jeremy M. Carr, Gregory S. Tschumper
• Format: Article
• Language: English
• Published: MDPI AG 2019-07-01
• Series: Molecules
• Subjects: intramolecular hydrogen bonding; semipinacol rearrangement; vibrational frequencies; density functional theory (DFT); coupled-cluster theory
• Online Access: https://www.mdpi.com/1420-3049/24/14/2523

A recent computational analysis of the stabilizing intramolecular OH⋯O contact in 1,2-dialkyl-2,3-epoxycyclopentanol diastereomers has been extended to thiiriane, aziridine and phosphirane analogues. Density functional theory (DFT), second-order M&#248;ller-Plesset perturbation theory (MP2) and CCSD(T) coupled-cluster computations with simple methyl and ethyl substituents indicate that electronic energies of the <inline-formula> <math display="inline"> <semantics> <mrow> <mi>c</mi> <mi>i</mi> <mi>s</mi> </mrow> </semantics> </math> </inline-formula> isomers are lowered by roughly 3 to 4 kcal mol^&#8722;1 when the OH group of these cyclopentanol systems forms an intramolecular contact with the O, S, N or P atom on the adjacent carbon. The results also suggest that S and P can participate in these stabilizing intramolecular interactions as effectively as O and N in constrained molecular environments. The stabilizing intramolecular OH⋯O, OH⋯S, OH⋯N and OH⋯P contacts also increase the covalent OH bond length and significantly decrease the OH stretching vibrational frequency in every system with shifts typically on the order of &#8722;41 cm^&#8722;1.