Highlights ► DFT techniques to explore the possibility of cytosine formation in interstellar space. ► Propynylidyne and cyanoacetylene are major sources of cytosine formation in gas and grains. ► Exothermic reactions with maximum barrier of 12.5kcal/mol. ► Global and local descriptors and QTAIM to understand mechanistic aspects of chemical reaction. ► Reactions with cyanoacetylene more probable to occur in the cold interstellar clouds.

    Abstract The detection of nucleic acid bases in carbonaceous meteorites suggests that their formation and survival is possible outside of the Earth. Small N-heterocycles, including pyrimidine, purines and nucleobases, have been extensively sought in the interstellar medium. It has been suggested theoretically that reactions between some interstellar molecules may lead to the formation of cytosine, uracil and thymine though these processes involve significantly high potential barriers. We attempted therefore to use quantum chemical techniques to explore if cytosine can possibly form in the interstellar space by radical–radical and radical-molecule interaction schemes, both in the gas phase and in the grains, through barrier-less or low barrier pathways. Results of DFT calculations for the formation of cytosine starting from some of the simple molecules and radicals detected in the interstellar space are being reported. Global and local descriptors such as molecular hardness, softness and electrophilicity, and condensed Fukui functions and local philicity indices were used to understand the mechanistic aspects of chemical reaction. The presence and nature of weak bonds in the molecules and transition states formed during the reaction process have been ascertained using Bader’s quantum theory of atoms in molecules (QTAIMs). Two exothermic reaction pathways starting from propynylidyne (CCCH) and cyanoacetylene (HCCCN), respectively, have been identified. While the first reaction path is found to be totally exothermic, it involves a barrier of 12.5kcal/mol in the gas phase against the lowest value of about 32kcal/mol reported in the literature. The second path is both exothermic and barrier-less. The later has, therefore, a greater probability of occurrence in the cold interstellar clouds (10–50K).


    Zugriff

    Zugriff prüfen

    Verfügbarkeit in meiner Bibliothek prüfen

    Bestellung bei Subito €


    Exportieren, teilen und zitieren



    Titel :

    Some new reaction pathways for the formation of cytosine in interstellar space – A quantum chemical study


    Beteiligte:
    Gupta, V.P. (Autor:in) / Tandon, Poonam (Autor:in) / Mishra, Priti (Autor:in)

    Erschienen in:

    Advances in Space Research ; 51 , 5 ; 797-811


    Erscheinungsdatum :

    2012-10-02


    Format / Umfang :

    15 pages




    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Elektronische Ressource


    Sprache :

    Englisch





    Relativistic interstellar space flight.

    Fishback, John Ford | DSpace@MIT | 1968

    Freier Zugriff

    Space Launch System Interstellar Probe

    Stough, Robert | NTRS | 2019


    Propulsion for interstellar space exploration

    Genta, G. / COSPAR | British Library Conference Proceedings | 2001


    A Small Interstellar Probe to the heliospheric boundary and interstellar space

    Mewaldt, R. A. / Kangas, J. / Kerridge, S. J. et al. | British Library Conference Proceedings | 1995