A touch of lavender: gas-phase structure and dynamics of the monoterpene linalool validated by microwave spectroscopy

Abstract

The microwave spectrum of linalool, an acyclic monoterpene, was recorded for the first time in the range from 9 to 16 GHz. The only conformer observed under molecular beam conditions was assigned. Fitting the rotational spectrum with two different programs treating internal rotation yielded the rotational constants A = 1.64674020(46) GHz, B = 0.68219862(16) GHz, C = 0.61875100(20) GHz, and the centrifugal distortion constants. The standard deviation of the fit was close to experimental accuracy. A-E splittings due to the internal rotation of one methyl group could be resolved and the internal rotation barrier was determined to be 400.20(64) cm(-1). The results from microwave spectroscopy were used to validate the molecular geometry obtained from quantum chemical calculations.

Flexibility unleashed in acyclic monoterpenes: conformational space of citronellal revealed by broadband rotational spectroscopy

“…9 The relative orientation of the aldehyde moiety with respect to the rest of the molecule is critical in establishing a relation between conformation and functionality. 45 Our observations are also consistent with previous reports that show that the origin of isopulegol isomer formation is strongly dependent on the energetically most-favoured chair-like conformations of (S)-citronellal. We also note that regardless if the preferred conformations are of the folded or unfolded type, the great majority of observed species utilises the aldehyde functional group to stabilise the overall structure, resulting in less electronic density available for intermolecular interactions to take place.…”

Favored Conformations of Carbonyl Compounds: A Structural Study of n‐Octanal

“…In the case of linalool,o nly one conformer exists under molecular beam conditions with no additional unassigned lines, [30] while for citronellal, 15 conformations could be observed. In this case the spectrum may become too dense foru nambiguous assignments, especially if the line intensities are weak.…”

Acetyl Methyl Torsion in N‐Ethylacetamide: A Challenge for Microwave Spectroscopy and Quantum Chemistry

“…On the other hand, the calculated and experimental A rotational constants differ by 177 MHz. This difference is very large compared to many other investigations on molecules of as imilars ize, [18,19] where the same methoda nd basis set were used andi tc auses the shift of approximately 1GHz between the predicted and experimental b-type Qbranch transitions. We additionally optimized the structure of conformer Iu sing variousm ethod/basis set combinations.T he results are summarized in Ta bleS-4.…”