Conformational Panorama of Cycloundecanone: A Rotational Spectroscopy Study

Abstract

The conformational landscape of the medium-size cyclic ketone cycloundecanone has been investigated using chirped-pulse Fourier transform microwave spectroscopy and computational calculations. Nine conformations were observed in the rotational spectrum and identified from the comparison of experimental and theoretical rotational constants as well as the observed and predicted types of rotational transitions. All singly substituted 13 C isotopologues were observed for the most abundant conformer, which allowed the determination of partial substitution and effective structures. The most abundant conformer dominates the rotational spectrum and is almost 40 times more abundant than the least abundant conformer. Conformational preferences are governed by the combination of transannular H···H and eclipsed HCCH interactions.

Assignment of the absolute configuration of molecules that are chiral by virtue of deuterium substitution using chiral tag molecular rotational resonance spectroscopy

“…This work has shown that CREST, a recently introduced tool for isomer searches in computational chemistry, successfully identifies low energy isomers of chiral tag complexes. This work supports the emerging consensus from the rotational spectroscopy community that CREST is a highly successful method for identifying the low‐energy isomers of weakly bound complexes 50,51,77–93 . Further, geometry optimization using dispersion corrected DFT gives chiral tag complex equilibrium geometries with sufficient accuracy to make a high‐confidence determination of the analyte absolute configuration.…”

“…This work supports the emerging consensus from the rotational spectroscopy community that CREST is a highly successful method for identifying the low-energy isomers of weakly bound complexes. 50,51,[77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93] Further, geometry optimization using dispersion corrected DFT gives chiral tag complex equilibrium geometries with sufficient accuracy to make a high-confidence determination of the analyte absolute configuration.…”

Binary conformers of a flexible, long-chain fluoroalcohol: dispersion controlled selectivity and relative abundances in a jet

“…To strive for an as complete as possible conformational search, we utilized CREST (Conformer-Rotamer Ensemble Sampling Tool), a powerful searching approach which combines semiempirical GFN-xTB 20 quantum chemistry methods with a metadynamics driven search algorithm, 21,22 in addition to manual potential energy surface (PES) scans along several important dihedral angles. The CREST approach has been successfully utilized by rotational spectroscopists for exploring conformational landscapes of a wide range of (in)organic compounds, 23,24 hydrogen-bonded clusters 25,26 and even very weakly bound van der Waals clusters. 27 About 1500 CREST binary TFB candidates were generated and a multi-tier approach 28 was used to identify low energy candidates.…”

The eight structures of caffeic acid: a jet-cooled laser ablated rotational study

“…These combined techniques have been established as an exceptionally robust tool to investigate the conformational landscape of many solid biomolecules [31][32][33][34][35] and, particularly, systems showing intricate conformational panoramas. [35][36][37][38][39][40] This experimental approach has been recently extended to the related trans-cinnamic and trans-p-coumaric phenolic acids. 41 In this work, we have examined the gas phase structure of caffeic acid using our broadband LA-CP-FTMW technique.…”