Formation of glycine in the interstellar medium : computational studies on various possible reaction paths

Ph.D. (Chemistry)Abstract: “How the most essential life elements, i.e., amino-acids, were formed in the interstellar medium (ISM)?” and “What are their roles in the evolution of life in our solar system?” are the two most intriguing questions, which are not yet answered exclusively as indicated in the works of many researchers. Among all the natural amino-acids, glycine (H2N-CH2-COOH) is not only an important biologically active molecule but also is the simplest as well as smallest amino-acid that can be found in all the biological entities found in the earth. The era of the astronomical search for glycine began as soon as the laboratory spectra for it were made available in 1978. Since then astrophysicists have been searching for this glycine in the ISM and many decades have been passed but still without any success. This is in spite of the fact that many amino-acid including the glycine have been found on meteorites, and moreover the distinct isotopic signature of those amino-acids are indicative of their extraterrestrial origin.However, detection of glycine in the interstellar medium is still ambiguous and the major problem arising in the analysis of a large cluster of weak lines collected through various high resolution telescopes. In this present work, using computational calculations many possible as well as favourable reaction paths, which can lead to the formation of Glycine in the interstellar conditions, have been investigated. Detailed mechanisms of those possible reaction paths have been investigated and also aptness of their feasibilities in the ISM has been discussed in the light of the prevailing interstellar conditions. From the mechanistic analysis of these possible reaction paths, it was observed that two of them show concerted type of mechanism, whereas others proceed through multi-stepped paths. One such concerted reaction discussed in this thesis encompasses the reaction of CH2=NH, CO and H2O leading to the formation of glycine. It was observed that this reaction..