Quantum chemical study of a new reaction pathway for the adenine formation in the interstellar space

¹ Department of PhysicsUniversity of Lucknow, 226007 Lucknow, India
e-mail: vpgpt1@gmail.com
² Department of Chemistry, University of Lucknow, 226007 Lucknow, India

Received: 10 August 2010
Accepted: 18 January 2011

Abstract

Gas phase chemistry in the cold interstellar clouds is dominated by ion-molecule and radical-radical interactions, though some neutral-neutral reactions are also barrier-free and efficient at cold temperatures. It has been suggested that it is impossible to synthesize detectable abundances of the pre-biotic HCN oligomer adenine (H₅C₅N₅) in the interstellar medium via successive neutral-neutral reactions. We attempted therefore to use quantum chemical techniques to explore if adenine can possibly form in the interstellar space by radical-radical and radical-molecule interaction schemes, both in the gas phase and in the grains. We report results of ab initio calculations for the formation of adenine starting from some of the simple neutral molecules and radicals detected in the interstellar space. The reaction path is found to be totally exothermic and barrier free, which increases the probability of occurrence in the cold interstellar clouds (10 − 50 K). We also estimated the reaction rates.