===== Ethyl Formate, C2H5OCHO, in the Interstellar Medium ===== A. Belloche, R. T. Garrod, H. S. P. Müller, K. M. Menten, C. Comito, and P. Schilke\\ reported on the\\ **[[https://doi.org/10.1051/0004-6361/200811550|Increased Complexity in Interstellar Chemistry: Detection and Chemical Modeling of Ethyl Formate and //n//-Propyl Cyanide in Sagittarius B2(N)]]**\\ //Astron. Astrophys.// **499**, (2009) 215–232.\\ See also the [[https://www.mpifr-bonn.mpg.de/pressreleases/2009/3|MPIfR press release]] (in English; German version also available).\\ In the group of the complex molecules detected by radio astronomical means, ethyl formate, C2H5OCHO, and //n//-propyl cyanide are among the largest. They have been detected in the famous massive star-forming region Sagittarius B2(N) in the course of a molecular line survey in the 3 mm frequency domain with additional observations at 2 and 1 mm carried out with the IRAM 30 m radio telescope.\\ [[molecules:ism:aan|Aminoacetonitrile]] was detected earlier in the course of this molecular line survey.\\ At a rotational temperature of about 100 K, very many transitions of ethyl formate have non-negligible intensities. However, many of them are blended severely with emissions or absorptions of other molecules. Nevertheless, a considerable number of transitions of the lower energy //anti//-conformer are not or only slightly blended. Its column density in Sgr B2(N) is similar to that of formic acid, and about a factor of 15 lower than that of methyl formate. The molecule was recently also identified in the Orion KL compact ridge region in the course of a molecular line survey carried out with the IRAM 30 m radio telescope.\\ B. Tercero, I. Kleiner, J. Cernicharo, H. V. L. Nguyen, A. López, and G. M. Muñoz Caro:\\ **[[https://doi.org/10.1088/2041-8205/770/1/L13|Discovery of Methyl Acetate and Gauche Ethyl Formate in Orion]]**\\ //Astrophys. J.// **770**, (2013) Art. No. L13.\\ Both conformers, //anti// and //gauche//, had about similar column densities, compatible with a kinetic temperature of 135 K. This agrees essentially with 150 K derived as rotational temperature of methyl acetate, which has a five times higher column density in this source than ethyl formate. Ethyl formate is the second ester and the second formate to be detected in the ISM after [[molecules:ism:methylformiat|methyl formate]]. The isomeric [[molecules:ism:meac|methyl acetate]] was also detected very recently. ---- Contributor(s): H. S. P. Müller; 04, 2009; 07, 2013 ----