Abstract
Background: Peptide bonds are among the fundamental building blocks of life, polymerizing amino acids to form proteins that make up the structural components of living cells and regulate biochemical processes. The detection of glycine by NASA in comet Wild 2 in 2009 suggests the possibility of the formation of biomolecules in extraterrestrial environments through the interstellar medium. Detected in the dense molecular cloud Sagittarius B2, acetamide is the largest molecule containing a peptide bond and is hypothesized to be the precursor to all amino acids; as such, viability of its formation is of important biological relevance.
 Methods: Under a proposed mechanism of ammonia and ketene reactants, which have also been detected in dense molecular clouds in the ISM, the reaction pathway for the formation of acetamide was modelled using quantum chemical calculations in Gaussian16, using Austin-Frisch-Petersson functional with dispersion density functional theory at a 6-31G(d) basis set level of theory to optimize geometries and determine the thermodynamic properties for the reaction. Stability of the reactants, transition states, and products were examined to establish a reasonable mechanism.
 Conclusion: Product formation of acetamide was found to be highly exergonic and exothermic with a low energy barrier, suggesting a mechanism that is viable in the extreme density and temperature conditions found in ISM.
Highlights
Of all the molecules discovered in the interstellar medium (ISM), acetamide (CH3CONH2) is of upmost importance because of its unique bond structure that has significant biological implications.Discovered in a dense molecular cloud of SagittariusB2 in 2006, it is the largest molecule discovered to date with a peptide bond (-CO-NH-)[1]
Product formation of acetamide was found to be highly exergonic and exothermic with a low energy barrier, suggesting a mechanism that is viable in the extreme density and temperature conditions found in ISM
The most likely synthesis came from ketene and ammonia, and structures were located and visually confirmed by intramolecular motions created by frequencies made in GaussView software[21]
Summary
Of all the molecules discovered in the interstellar medium (ISM), acetamide (CH3CONH2) is of upmost importance because of its unique bond structure that has significant biological implications.Discovered in a dense molecular cloud of SagittariusB2 in 2006, it is the largest molecule discovered to date with a peptide bond (-CO-NH-)[1]. Of all the molecules discovered in the interstellar medium (ISM), acetamide (CH3CONH2) is of upmost importance because of its unique bond structure that has significant biological implications. The ISM is often cited when discussing prebiotic chemistry, as this large territory between star systems contains many unique environments where many organic molecules have been discovered[2,3]. These molecules containing C, H, O, and N are essential to all living systems, that consist of proteins. The core components of peptide bonds have been discovered through isocyanic acid (HNCO), formamide (HCONH2), and acetamide[4]. Determining individual reactions can help establish patterns in other reactions including transition state structures, plausibility, energy barriers, mechanisms, and kinetics in the ISM
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