Allyl alcohol is a strong lachrymator with a pungent mustard odor. It is a fundamental building block of several smelling organic molecules. Depending on the carbon frame, they present a quite different odor, suggesting a modulation role of the molecular shape in the ligand-receptor interaction. Rotational spectroscopy is a suitable tool to get insights on the structure of molecules and molecular complexes in the gas phase and, in combination with computational chemistry simulations, allows for exploration of high dimension conformational spaces. Here we present, for the first time, the rotational spectra and the analysis of three allyl alcohols: oct-1-en-3-ol (mushroom alcohol, C10H16O), 4,6,6-trimethylbicyclo[3.1.1]hept-3-en-2-ol (verbenol, C8H16O), and 3,7,11-trimethyl-2,6,10-dodecatrien-1-ol (farnesol, C15H26O). The spectrum of oct-1-en-3-ol has been collected in the 59.6-74.4 GHz frequency range with the free jet absorption millimeter wave spectrometer in Bologna. Two species were observed. In both of them the allyl alcohol substructure is skew-gauche (referring to OCC=C and HOCC diehdral angles, respectively) and the alkyl chain is all trans. The difference lies on the relative orientation of the alkyl and allyl alcohol subunits. The spectrum of cis-verbenol has been recorded in the 2-8 GHz frequency range with the chirpedpulse Fourier transform spectrometer in Valladolid. The rotational spectra of the parent, hydroxyl deuterated, and all ¹³C-isotopologues have been assigned, allowing for structure’s determination. Differently from solid state, in the gas phase the most stable conformer exhibits an anti HCOH arrangement. Observation of the 1:1 water complex has shown that water acts as proton donor to the hydroxyl group, forming a secondary O-H interaction with alkyl verbenol’s hydrogen atoms. With the same spectrometer, the spectrum of farnesol has been collected. Since farnesol is formed by a mixture of 4 cis/trans-isomers, the spectrum is quite congested and, due to the presence of 8 rotatable bonds, the assignment is not straightforward. Preliminary considerations on the conformational space will be presented.
maris assimo, susana blanco (2018). Rotational spectroscopy signature of smelling allyl alcohols. Bilbao : Universidad del País Vasco (upv-ehu) / Universidad de Valladolid (uva).
Rotational spectroscopy signature of smelling allyl alcohols
maris assimo
;
2018
Abstract
Allyl alcohol is a strong lachrymator with a pungent mustard odor. It is a fundamental building block of several smelling organic molecules. Depending on the carbon frame, they present a quite different odor, suggesting a modulation role of the molecular shape in the ligand-receptor interaction. Rotational spectroscopy is a suitable tool to get insights on the structure of molecules and molecular complexes in the gas phase and, in combination with computational chemistry simulations, allows for exploration of high dimension conformational spaces. Here we present, for the first time, the rotational spectra and the analysis of three allyl alcohols: oct-1-en-3-ol (mushroom alcohol, C10H16O), 4,6,6-trimethylbicyclo[3.1.1]hept-3-en-2-ol (verbenol, C8H16O), and 3,7,11-trimethyl-2,6,10-dodecatrien-1-ol (farnesol, C15H26O). The spectrum of oct-1-en-3-ol has been collected in the 59.6-74.4 GHz frequency range with the free jet absorption millimeter wave spectrometer in Bologna. Two species were observed. In both of them the allyl alcohol substructure is skew-gauche (referring to OCC=C and HOCC diehdral angles, respectively) and the alkyl chain is all trans. The difference lies on the relative orientation of the alkyl and allyl alcohol subunits. The spectrum of cis-verbenol has been recorded in the 2-8 GHz frequency range with the chirpedpulse Fourier transform spectrometer in Valladolid. The rotational spectra of the parent, hydroxyl deuterated, and all ¹³C-isotopologues have been assigned, allowing for structure’s determination. Differently from solid state, in the gas phase the most stable conformer exhibits an anti HCOH arrangement. Observation of the 1:1 water complex has shown that water acts as proton donor to the hydroxyl group, forming a secondary O-H interaction with alkyl verbenol’s hydrogen atoms. With the same spectrometer, the spectrum of farnesol has been collected. Since farnesol is formed by a mixture of 4 cis/trans-isomers, the spectrum is quite congested and, due to the presence of 8 rotatable bonds, the assignment is not straightforward. Preliminary considerations on the conformational space will be presented.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
