NASA Astrobiology Institute (NAI)

1. Formation of Nitrogenated Aromatics in the Interstellar Medium

   Project Investigators: Alessandra Ricca

   Other Project Members

   M.S. El-Shall (Collaborator)

   Summary

   We are investigating the chemical energetics and plausibility of reaction pathways leading to the formation of nitrogenated aromatics suggestive of purine and pyrimidine bases of RNA and DNA molecules using quantum chemistry.

   Astrobiology Roadmap Objectives:

   • Objective 3.1: Sources of prebiotic materials and catalysts

   Project Progress

   Alessandra Ricca- We are investigating the chemical energetics and plausibility of reaction pathways leading to the formation of nitrogenated aromatics suggestive of purine and pyrimidine bases of RNA and DNA molecules using quantum chemistry. We have worked in collaboration with Prof. M. Samy El-Shall at Virginia Commonwealth University who has studied the reactions of benzene ion and pyridine radical cation with acetylene over a wide temperature range, from 120 to 650 K, using the mass-selected ion mobility (drift cell) technique. Experiments shows that acetylene undergoes sequential additions onto the benzene radical cation with two different mechanisms operating at low and high temperature. Our calculations simulated the low temperature regime and agree with the experimental results. A manuscript entitled “Formation of Complex organics from Acetylene Catalyzed by Ionized Benzene” by P. O. Momoh, A. Soliman, M. S. El-Shall and A. Ricca has been submitted to J. Amer. Chem. Soc. A manuscript on the reactions of pyridine radical cation with acetylene is in preparation. These findings show that complex organics can form even under a wide range of conditions that can be found in outer space environments. In addition, we are investigating the reactivity of N⁺ with various unsaturated hydrocarbons, such as 1,3-butadiene, to form small nitrogenated heterocycles.

Publications

Bauschlicher, C.W., Liu, Y., Ricca, A., Mattioda, A.L. & Allamandola, L.J.  (2007).  Electronic and Vibrational Spectroscopy of Diamondoids and the Interstellar Infrared bands between 3.35 and 3.55 microns.  Astrophys. J., 671:458-469.

Momoh, P.O., Soliman, A., El-Shall, M.S. & Ricca, A.  (Submitted).  Formation of Complex organics from Acetylene Catalyzed by Ionized Benzene.  J. Amer. Chem. Soc..

Ricca, A., Bakes, E.L.O. & Bauschlicher, C.W.  (2007).  The energetics for hydrogen addition to naphthalene cations.  Astrophys. J., 659:858-861.

Ricca, A. & Bauschlicher, C.W.  (Submitted).  The gas-phase catalytic formation of H2 by cations.  Astrophys. J..