C5H9N isomers: pointers to possible branched chain interstellar molecules

Abstract

Abstract:The astronomical observation of isopropyl cyanide further stresses the link between the chemical composition of the ISM and molecular composition of the meteorites in which there is a dominance of branched chain amino acids as compared to the straight. However, observations of more branched chain molecules in ISM will firmly establish this link. In the light of this, we have considered C 5 H 9 N isomeric group in which the next higher member of the alkyl cyanide and other branched chain isomers belong. High-level quantum chemical calculations have been employed in estimating accurate energies of these isomers. From the results, the only isomer of the group that has been astronomically searched, n-butyl cyanide is not the most stable isomer and therefore, which might explain why its search could only yield upper limits of its column density without a successful detection. Rather, the two most stable isomers of the group are the branched chain isomers; tertbutylnitrile and isobutyl cyanide. Based on the rotational constants of these isomers, it is found that the expected intensity of tert-butylnitrile is the maximum among this isomeric group. Thus, this is proposed as the most probable candidate for astronomical observation. A simple LTE (Local thermodynamic equilibrium) modelling has also been carried out to check the possibility of detecting tert-butyl cyanide in the millimetre-wave region.

Computational Studies on C3H4N2 Isomers

“…The optimized structures were found to be stable with no imaginary frequency as shown from the frequency calculations. [10][11][12][13][14][15][16][17][18][19][20] …”

“…G4 level of calculations are mostly used for geometry optimization, Zero Potential Energy ZPE, Single Point calculations etc. [5][6][7] C 3 H 4 N 2 isomeric group consists of important biological molecules; the imidazole ring structure occurs in fundamental biological molecules such as histidine (an amino acid) and purines; imidazolium and pyrazolium-based ionic surface are now receiving attention of researches as good materials for biosensing; pyrazole and its derivatives are important constituents of many drugs because of their muscle relaxing, antidiabetic, analgesic, anti-inflammatory, and other biological activities. [8,9] As important as the molecules are, some of them have not really been studied experimentally partly due to their unstable nature and as such some of their potential applications are still not known.…”

Quantum Chemical Calculations on Silicon Monoxide (SiO) and its Protonated Analogues

“…Different computational methods have been employed in this study; these include the Hartree Fock (HF), B3LYP, the MP2 method, the CCSD and the Gaussian 04 compound method (Etim and Arunan, 2015;2016;2017;Etim, et.al., 2016;2017). The choice of these methods is based on experience as some methods perform well for some properties than other methods.…”

“…Quantum mechanics complements the classical mechanics because it takes into full consideration the wavelike properties of matter while finding solution to chemical problems. Quantum mechanics forms the bedrock on which most computational chemistry calculations are built (Etim et al, 2016;2017).…”

Vibrational-Rotational Spectra of Normal Acetylene and Doubly Deuterated Acetylene: Experimental and Computational Studies

“…With the collaboration between the spectroscopists and the astrophysicists initiated with the purpose of assigning the Fraunhofer lines in the solar spectrum to atomic transitions in the 18 th century over 200 different molecular species in the interstellar medium (ISM). These molecular species range from the simple diatomics like hydrogen molecular, carbon monoxide, etc., to the complex molecular species (those with six atoms and above) up to those the RESEARCH ARTICLE bulky balls like the C 60 , C 70 , etc., with each of these molecular species telling us the story of the chemistry and physics of the environment from which they were detected [1][2][3][4][5][6][7][8] . Acetylene, (C 2 H 2 )-a known interstellar molecular species is an important organic compound belonging to the alkyne family.…”