Flexible molecules show a complex conformational space, generally shaped by non bonding interactions occurring within the molecule or with the surroundings and represent therefore a challenge for computational methods and rotational spectroscopy because of the presence of high number of stable conformations and large amplitude motions. We report the rotational study of 2(N)-methylaminoethanol (MAE) performed by Free Jet Absorption Microwave Spectrocopy (FJAMW). This choice of study the conformational properties of MAE is mainly due to the fact that aminoethanol and thus also MAE can be considered a precursors of aminoacids in the interstellar medium (1) and secondly, the methyl-aminoethanol side chain is present in important biological molecules such as adrenaline, so we can consider it like a model for the chain’s interactions. The high vacuum conditions that we obtained with this technique reproduce those of the interstellar medium and this makes these kind of experiments very useful to guide astrophysical studies that aim at finding life precursors. Infact, because of the unique spectral signatures provided by rotational spectroscopy, much of the chemical inventory of the interstellar medium has been detected using radio telescopes operating in the centimeter and millimeter wavelenghts regions (2). Moreover the unusual chemical environments in this spatial region can produce novel chemical reaction processes, that involve less stable conformational species. The conformational preferences of MAE are dominated by the intramolecular hydrogen bond between the OH and NH2 groups. The high flexibility of this molecule involves a complex energy potential surface with a large number of possible stable conformations. Infact for MAE 24 stable conformations have been predicted and two conformers were observed by FJAMW spectroscopy with our 60-72 GHz spectrometer. With respect to a previous study (3) we have extended the frequency range to 72 GHz and partly reassigned the rotational spectrum of one of the conformers. (1) S. Charnley , in Proceedings of the workshop: The bridge between the Big Bang and Biology, CNR, Italy 1999. (2) J. L. Neill et all., J. Phys. Chem. A, 2011, 115 (24), pp 6472–6480. (3) R. E. Penn and L.W. Buxton, J. Mol. Spectrosc. 56, 229, 1975.
The rotational study of a flexible molecule: 2(N)-methylaminoethanol A challenge for rotational spectrosopy
CALABRESE, CAMILLA;MELANDRI, SONIA;MARIS, ASSIMO
2012
Abstract
Flexible molecules show a complex conformational space, generally shaped by non bonding interactions occurring within the molecule or with the surroundings and represent therefore a challenge for computational methods and rotational spectroscopy because of the presence of high number of stable conformations and large amplitude motions. We report the rotational study of 2(N)-methylaminoethanol (MAE) performed by Free Jet Absorption Microwave Spectrocopy (FJAMW). This choice of study the conformational properties of MAE is mainly due to the fact that aminoethanol and thus also MAE can be considered a precursors of aminoacids in the interstellar medium (1) and secondly, the methyl-aminoethanol side chain is present in important biological molecules such as adrenaline, so we can consider it like a model for the chain’s interactions. The high vacuum conditions that we obtained with this technique reproduce those of the interstellar medium and this makes these kind of experiments very useful to guide astrophysical studies that aim at finding life precursors. Infact, because of the unique spectral signatures provided by rotational spectroscopy, much of the chemical inventory of the interstellar medium has been detected using radio telescopes operating in the centimeter and millimeter wavelenghts regions (2). Moreover the unusual chemical environments in this spatial region can produce novel chemical reaction processes, that involve less stable conformational species. The conformational preferences of MAE are dominated by the intramolecular hydrogen bond between the OH and NH2 groups. The high flexibility of this molecule involves a complex energy potential surface with a large number of possible stable conformations. Infact for MAE 24 stable conformations have been predicted and two conformers were observed by FJAMW spectroscopy with our 60-72 GHz spectrometer. With respect to a previous study (3) we have extended the frequency range to 72 GHz and partly reassigned the rotational spectrum of one of the conformers. (1) S. Charnley , in Proceedings of the workshop: The bridge between the Big Bang and Biology, CNR, Italy 1999. (2) J. L. Neill et all., J. Phys. Chem. A, 2011, 115 (24), pp 6472–6480. (3) R. E. Penn and L.W. Buxton, J. Mol. Spectrosc. 56, 229, 1975.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
