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Session 20 - Chemistry & Physical Process in the ISM.
Display session, Wednesday, January 07
Exhibit Hall,

[20.09] A New Interstellar Cyclic Molecule, Ethylene Oxide

J. E. Dickens, W. M. Irvine (FCRAO U. Massachusetts-Amherst), M. Ohishi, M. Ikeda, S. Ishikawa (Nobeyama Radio Obs.), A. Nummelin, A. Hjalmarson (Onsala Space Obs.)

Ethylene oxide (c-C2H4O) is only the fourth known ring molecule identified in the interstellar medium, detected in the Galactic Center cloud SgrB2(N) by Dickens et al. (1997). It is the higher energy isomer of both the more familiar interstellar species acetaldehyde (CH3CHO) and the as yet undetected molecule vinyl alcohol (CH2CHOH). Dickens et al. (1997) reported a c-C2H4O molecular column density about an order of magnitude less than that reported for CH3CHO in SgrB2(N). This is a factor of 200 larger than the predictions of the new standard gas phase chemistry model of Lee, Bettens, and Herbst (1996), suggesting that the formation of c-C2H4O may be related to molecular formation on interstellar grains. We present observations of the c-C2H4O to CH3CHO abundance ratio in 5 additional molecular clouds. The data were taken in October 1997 with the Swedish-European Submillimeter Telescope in Chile. The confirmation of ethylene oxide in molecular clouds provides an appealing scenario for the first link in the chain of reactions leading to the origin of life, since it has been suggested as a possible pathway to the formation of the related cyclic molecule oxiranecarbonitrile (c-C3H3NO; cf., Dickens et al. 1996), a precursor to the synthesis of sugar phosphates which comprise the backbone of our molecular genetic structure. References: Dickens, J.E., Irvine, W.M., Ohishi, M., Ikeda, M., Ishikawa, S., Nummelin, A., and Hjalmarson, A. 1997, Astrophys. J., 489 (in press). Dickens, J.E. et al. 1996, Orig. Life Evol. Biosphere, 26, 97. Lee, H.-H., Bettens, R.P.A., and Herbst, E. 1996, Astron. Astrophys. Supp., 119, 111.

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