Glycine （C2H5NO2） was the first amino acid to be detected in space by the stardust space probe in Comet Wild2, and is used by living organisms to make proteins. We discuss three different reaction paths for the form...Glycine （C2H5NO2） was the first amino acid to be detected in space by the stardust space probe in Comet Wild2, and is used by living organisms to make proteins. We discuss three different reaction paths for the formation of glycine in interstellar space from some simpler molecules detected in the interstellar medium. The possibility of the formation of glycine in interstellar space is considered by radicalradical and radical-molecule interaction schemes using quantum chemical calculations with density functional theory at the B3LYP/6-31G （d,p） level. In the chemical pathways we discuss, a few reactions are found to be totally exothermic and barrierless while others are endothermic with a very small reaction barrier, thus giving rise to a high probability of forming glycine in interstellar space.展开更多
The three isomers of C2H4O2,viz.,glycolaldehyde(HCOCH2 OH),acetic acid(CH3 COOH)and methyl formate(HCOOCH3),have been detected in copious amounts in the interstellar medium(ISM).The possibility for formation of these ...The three isomers of C2H4O2,viz.,glycolaldehyde(HCOCH2 OH),acetic acid(CH3 COOH)and methyl formate(HCOOCH3),have been detected in copious amounts in the interstellar medium(ISM).The possibility for formation of these molecules through interstellar formaldehyde(HCHO)has been explored by using the quantum chemical approach described by density functional theory(DFT)and second order Moller-Plesset perturbation(MP2)theory with a 6–311 G(d,p)basis set in the gas phase as well as in icy grains.The associated molecule-molecule interactions have been discussed to study the formation of isomers of C2H4O2 in ISM.The reactions of two formaldehyde molecules exhibit a considerable potential barrier but due to quantum tunneling,these reactions could be possible in ISM.The chemical pathway is exothermic,which gives rise to a high probability for the formation of all three isomers,viz.glycolaldehyde,methyl formate and acetic acid,in interstellar space.Anharmonic rotational vibration,centrifugal distortion constants and coupling constants are also calculated and results suggest that the vibrations are harmonic in nature.展开更多
Recently a new molecule, cyanomethamine, has been detected towards Sagittarius B2（N） （Sgr B2（N））. Studying the formation mechanisms of complex interstellar molecules is difficult. Hence, a theoretical quantum ch...Recently a new molecule, cyanomethamine, has been detected towards Sagittarius B2（N） （Sgr B2（N））. Studying the formation mechanisms of complex interstellar molecules is difficult. Hence, a theoretical quantum chemical approach for analyzing the reaction mechanism describing the forma- tion of interstellar cyanomethamine through detected interstellar molecules and radicals （NCCN＋H） is discussed in the present work. Calculations are performed by using quantum chemical techniques, such as Density Functional Theory （DFT） and Mφ11er-Plesset perturbation （MP2） theory with a 6-311G（d,p） basis set, both in the gas phase and in icy grains. The proposed reaction path （NCCN＋H＋H） has exother- micity with no barrier which indicates the possibility of cyanomethamine formation in the interstellar medium.展开更多
The interstellar medium, filling the vast space between stars, is a rich reser-voir of molecular material ranging from simple diatomic molecules to more com-plex, astrobiologically important molecules such as vinylcya...The interstellar medium, filling the vast space between stars, is a rich reser-voir of molecular material ranging from simple diatomic molecules to more com-plex, astrobiologically important molecules such as vinylcyanide, methylcyanodiac-cetylene, cyanoaUene, etc. Interstellar molecular cyanoallene is one of the most stableisomers of methylcynoacetylene. An attempt has been made to explore the possibilityof forming cyanoallene in interstellar space by radical-radical and radical-moleculeinteraction schemes in the gaseous phase. The formation of cyanoallene starting fromsome simple, neutral interstellar molecules and radicals has been studied using densityfunctional theory. The reaction energies and structures of the reactants and productsshow that the formation of cyanoallene is possible in the gaseous phase. Both of theconsidered reaction paths are totally exothermic and barrierless, thus giving rise to ahigh probability of occurrence. Rate constants for each step in the formation processof cyanoallene in both the reaction paths are estimated. A full vibrational analysishas been attempted for cyanoallene in the harmonic and anharmonic approximations.Anharmonic spectroscopic parameters such as rotational constants, rotation-vibrationcoupling constants and centrifugal distortion constants have been calculated.展开更多
基金Financial support to the authors Alka Misra and Shivani from University Grant Commission (UGC)Government of India is gratefully acknowledged through a major research project
文摘Glycine （C2H5NO2） was the first amino acid to be detected in space by the stardust space probe in Comet Wild2, and is used by living organisms to make proteins. We discuss three different reaction paths for the formation of glycine in interstellar space from some simpler molecules detected in the interstellar medium. The possibility of the formation of glycine in interstellar space is considered by radicalradical and radical-molecule interaction schemes using quantum chemical calculations with density functional theory at the B3LYP/6-31G （d,p） level. In the chemical pathways we discuss, a few reactions are found to be totally exothermic and barrierless while others are endothermic with a very small reaction barrier, thus giving rise to a high probability of forming glycine in interstellar space.
基金financial support to A.Misra(PI)and Shivani(RA)from the Council of Science&Technology(CST)under major research project(CST/4053)is gratefully acknowledged
文摘The three isomers of C2H4O2,viz.,glycolaldehyde(HCOCH2 OH),acetic acid(CH3 COOH)and methyl formate(HCOOCH3),have been detected in copious amounts in the interstellar medium(ISM).The possibility for formation of these molecules through interstellar formaldehyde(HCHO)has been explored by using the quantum chemical approach described by density functional theory(DFT)and second order Moller-Plesset perturbation(MP2)theory with a 6–311 G(d,p)basis set in the gas phase as well as in icy grains.The associated molecule-molecule interactions have been discussed to study the formation of isomers of C2H4O2 in ISM.The reactions of two formaldehyde molecules exhibit a considerable potential barrier but due to quantum tunneling,these reactions could be possible in ISM.The chemical pathway is exothermic,which gives rise to a high probability for the formation of all three isomers,viz.glycolaldehyde,methyl formate and acetic acid,in interstellar space.Anharmonic rotational vibration,centrifugal distortion constants and coupling constants are also calculated and results suggest that the vibrations are harmonic in nature.
基金the University Grant Commission(UGC)supported by a major research project+2 种基金supported by a UGC research awardISRO major research projectthe UGC BSR Meritorious Fellowship
文摘Recently a new molecule, cyanomethamine, has been detected towards Sagittarius B2（N） （Sgr B2（N））. Studying the formation mechanisms of complex interstellar molecules is difficult. Hence, a theoretical quantum chemical approach for analyzing the reaction mechanism describing the forma- tion of interstellar cyanomethamine through detected interstellar molecules and radicals （NCCN＋H） is discussed in the present work. Calculations are performed by using quantum chemical techniques, such as Density Functional Theory （DFT） and Mφ11er-Plesset perturbation （MP2） theory with a 6-311G（d,p） basis set, both in the gas phase and in icy grains. The proposed reaction path （NCCN＋H＋H） has exother- micity with no barrier which indicates the possibility of cyanomethamine formation in the interstellar medium.
文摘The interstellar medium, filling the vast space between stars, is a rich reser-voir of molecular material ranging from simple diatomic molecules to more com-plex, astrobiologically important molecules such as vinylcyanide, methylcyanodiac-cetylene, cyanoaUene, etc. Interstellar molecular cyanoallene is one of the most stableisomers of methylcynoacetylene. An attempt has been made to explore the possibilityof forming cyanoallene in interstellar space by radical-radical and radical-moleculeinteraction schemes in the gaseous phase. The formation of cyanoallene starting fromsome simple, neutral interstellar molecules and radicals has been studied using densityfunctional theory. The reaction energies and structures of the reactants and productsshow that the formation of cyanoallene is possible in the gaseous phase. Both of theconsidered reaction paths are totally exothermic and barrierless, thus giving rise to ahigh probability of occurrence. Rate constants for each step in the formation processof cyanoallene in both the reaction paths are estimated. A full vibrational analysishas been attempted for cyanoallene in the harmonic and anharmonic approximations.Anharmonic spectroscopic parameters such as rotational constants, rotation-vibrationcoupling constants and centrifugal distortion constants have been calculated.
