Looking for homochirality in the inter-stellar medium

Abstract

In this report we address the question of whether some chiral molecules have a probability of being detected in the interstellar medium (ISM). To this end we rely on the Minimum Energy Principle which states that the most abundant isomer of a given generic formula should be that of lowest energy. The relative stability of the chiral molecules with respect to the other possible species of the same chemical formula are calculated by means of quantum simulations based on density functional theory (DFT). The result is that no chiral isomer in the C(3)H(6)O (acetone), C(2)H(5)ON, C(3)H(7)ON (amide), C(2)H(5)O(2)N, C(3)H(7)O(2)N (amino acid) families is the most stable species. This is also true of the C(2)(H(2)O)(2) and C(3)(H(2)O)(3) species when restricted to the sugar families, but another chiral molecule of the same chemical formula, i.e. lactic acid HOCH(CH(3))COOH is the most stable of all structures. Two other molecules with an NH(2) group, namely, NH(2)CH(CH(3))CN, the precursor of alpha-alanine and NH(2)CH(CH(3))OH, the simplest chiral molecule, are also the most stable species in their respective families. These three molecules satisfy the conditions for being detected according to the Minimum Energy Principle. With dipoles moments of 2.3, 2.7 and 1.6 Debye respectively, they make appealing targets. The present study should encourage laboratory experiments to determine rotational constants of higher precision prior to submission of observation proposals.