CODECS 2013 Workshop. San Lorenzo de El Escorial, Madrid, 18th –22nd April, 2013
Low-Frequency Modes of Methyl Acetate
M.L. Senenta, R. Domínguez-Gómezb, M. Carvajalc, I. Kleinerd
a
Dpto. Química y Física Teóricas, Instituto de Estructura de la Materia, CSIC, Madrid, Spain
b
Dpto. Ingeniería Civil, Cátedra de Química, Universidad Politécnica de Madrid, Spain
c
Dpto. Física Aplicada, Unidad Asociada CSIC-IEM, Universidad de Huelva, Spain
d
Laboratoire Interuniversitaire des Systèmes Atmospheriques (LISA), CNRS, Université de
Paris-Est et Paris Diderot, France
senent@iem.cfmac.csic.es
Methyl acetate (MeOAc, CH3COOCH3, Fig 1) is a flammable liquid occasionally used as
a solvent because the low toxicity and fast evaporation rate. In gas phase, it represents one
relevant prebiotic astrophysical molecule which further detection can be expected given the
capability of the new ALMA observatory.
The presence of MeOAc in gas phase astrophysical sources was postulated because relate
molecules such as methyl formate, acetic acid and many other organic compounds containing
methyl groups are listed as astrochemical species. MeOAc shows low frequency modes which
excited levels can be populated at the hot cores temperatures.
In the present paper, we use highly correlated ab initio methods to determine as much as
possible spectroscopic parameters searching to help experimental assignments. To determine low
energy levels of the CH3COOCH3 isotopologue1, we solve variationally a three-dimensional
Hamiltonian whose independent coordinates are the three torsional coordinates. This model
allows us to discuss previous assignments and to evaluate the effect of interactions between the
central bond torsion and the methyl torsions.
There is a very good agreement between the parameters fitted by Tudorie, Kleiner et al. 2
using 800 microwave and millimeter-wave transitions of cis-methyl acetate. Very small terms
describing interactions between methyl groups are found.
Fig. 1
.
References
1. M.L.Senent, R. Domínguez-Gómez, M.Carvajal and I.Kleiner, “CCSD(T) Study of the Far Infrared
Spectra of Methyl Acetate”, J.Chem.Phys., XX, XX (2013)
2. M.Tudorie, I.Kleiner, J.T.Hougen, S.Melandri, L.W.Sutikdja and W.Stahl, J.Mol.Spectrosc., 269, 211
(2011)