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

Abstract

The conformational landscape of 22 different non, mono-, and disubstituted compounds with a fivemembered ring was thoroughly explored by ab initio (MP2) and DFT (B3LYP and M06-2X) methods with the 6-311+G** basis set. Our results showed that the conformational preference of these compounds was governed mainly by the specific characteristics of the substituents, with a minor influence of the level of theory employed. After a detailed analysis of the computational data, we found an interesting preference of the electronegative substituents to take pseudo-axial positions, whereas alkyl groups preferred adopting the pseudo-equatorial locations. Such preferences were pronounced with MP2 and M06-2X and underestimated by B3LYP. Despite each level of theory affording different landscapes in many cases, as a general trend, we noticed that M06-2X afforded much higher correlation with the MP2 results than B3LYP. View Article Online3 E (0.90 kcal mol À1 ) was 0.83-0.97 kcal mol À1 lower than those This journal is

Fluorinated Rings: Conformation and Application

“…shifting towards the equivalent 5 T 4 / 5 E and 2 T 3 / 2 E conformations which are connected through the non-equivalent envelopelike transition structures 1 E and E 1 . [45] Notably, the 5 T 4 / 5 E (or 2 T 3 / 2 E) conformer is favored by 0.15-0.92 kcal mol À1 and by 1.49-2.46 kcal mol À1 over the E 1 and 1 E conformers, respectively (Figure 5). [45] Owing to the flexible conformational behavior of fluorinated cyclopentanes, there has been some interest in the preparation of their mono-and recently multi-fluorinated ana-logues, such as the all-cis-1,2,3,4-tetrafluorocyclopentane 15 (Figure 5).…”

“…[45] Notably, the 5 T 4 / 5 E (or 2 T 3 / 2 E) conformer is favored by 0.15-0.92 kcal mol À1 and by 1.49-2.46 kcal mol À1 over the E 1 and 1 E conformers, respectively (Figure 5). [45] Owing to the flexible conformational behavior of fluorinated cyclopentanes, there has been some interest in the preparation of their mono-and recently multi-fluorinated ana-logues, such as the all-cis-1,2,3,4-tetrafluorocyclopentane 15 (Figure 5). [46,47] The X-ray analysis of the latter indicates an envelope conformation with an axial fluorine at the tip.…”

“…Conformational preference of fluorocyclopentane. The calculated energy differences (DE) in gas phase are given in kcal mol À1 [45].…”

Computational study of inversion‐topomerization pathways in 1,3‐dimethylcyclohexane and 1,4‐dimethylcyclohexane: Ab initio conformational analysis

“…As the study of cycloalkanes, focusing on their molecular preferences, conformational behaviors, and relative energies, has long been a topic of interest for chemistry and some interrelated application, they have been investigated by theoretical calculations and experimental measurement [1‐11]. The adopted experimental methods briefly include X‐ray diffraction, Raman, infrared, and NMR spectrum detection, [9, 11‐14] and theoretical approaches contain ab initio, molecular force field, and dynamical density functional theory [7, 8, 10, 15].…”

“…As the study of cycloalkanes, focusing on their molecular preferences, conformational behaviors, and relative energies, has long been a topic of interest for chemistry and some interrelated application, they have been investigated by theoretical calculations and experimental measurement [1‐11]. The adopted experimental methods briefly include X‐ray diffraction, Raman, infrared, and NMR spectrum detection, [9, 11‐14] and theoretical approaches contain ab initio, molecular force field, and dynamical density functional theory [7, 8, 10, 15]. These previous studies usually cover two mainly aspects: (1) conformational determination of the simple neutral cycloalkane compounds from three‐membered ring to the larger ones, like cyclohexane, cyclooctane, and cyclotridecane [10, 15, 16]; (2) conformational changing investigation of cyclohexane and its substitution derivatives [1, 5, 12, 14, 17‐19].…”