The tautomerization of H_2NCH_2C(OH)NH to H_2NCH_2CONH_2 in the interstellar medium  

作　　者：XU SiChuan DENG ShengRong MA LiYing SHI Qiang ZHANG XingKang GE MaoFa 

机构地区：[1]Key Laboratory of Ministry of Education for Medicinal Chemistry of Natural Resource, College of Chemical Science and Technology, Laboratory on the Origin of Life, Yunnan University, Kunming 650091, China [2]State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China

出　　处：《Science China(Physics,Mechanics & Astronomy)》2011年第1期156-163,共8页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the One-Hundred-Talents Project of Chinese Academy of Sciences,and the Academic Talent Foundation of Yunnan Province,China (Grant No.2006PY01-29)

摘　　要：The tautomerization of H2NCH2C(OH)NH to H2NCH2CONH2 is an important step by way of Strecker synthesis for the production of glycine in the interstellar medium (ISM) with respect to the origin of amino acids on the early Earth.Our work indicates two mechanisms for the tautomerization to occur.k CVT/SCT (rate constant) is 45.6s-1 at 50 K,obtained with the small curvature tunneling (SCT) approximation and canonical variational transition state theory (CVT),to support one mechanism assisted by quantum tunneling in the ISM.Another mechanism is through the (H2O) 2-coupled proton transfer.In the (H2O)2 coupled reaction,two H2O molecules act as a catalyst to reduce the barrier energy by 23.7 kcal mol 1,and cooperatively let a proton pass a hydrogen-bonded bridge composed of H2NCH2C(OH)NH with (H2O)2.kTST is 8.08×10-4 s-1 at 100 K,calculated with TST kinetics,to demonstrate the mechanism.Therefore,the tautomerization is feasible in the ISM.H2NCH2C(OH)NH and H2NCH2CONH2 will be detected in the ISM and found in carbonaceous chondrites.The results present new evidence for the third theory on the origin of amino acids on the early Earth.The tautomerization of H2NCH2C（OH）NH to H2NCH2CONH2 is an important step by way of Strecker synthesis for the production of glycine in the interstellar medium （ISM） with respect to the origin of amino acids on the early Earth.Our work indicates two mechanisms for the tautomerization to occur.k^CVT/SCT （rate constant） is 45.6s^-1 at 50 K,obtained with the small curvature tunneling （SCT） approximation and canonical variational transition state theory （CVT）,to support one mechanism assisted by quantum tunneling in the ISM.Another mechanism is through the （H2O） 2-coupled proton transfer.In the （H2O）2 coupled reaction,two H2O molecules act as a catalyst to reduce the barrier energy by 23.7 kcal mol^- 1,and cooperatively let a proton pass a hydrogen-bonded bridge composed of H2NCH2C（OH）NH with （H2O）2.k^TST is 8.08×10^-4 s^-1 at 100 K,calculated with TST kinetics,to demonstrate the mechanism.Therefore,the tautomerization is feasible in the ISM.H2NCH2C（OH）NH and H2NCH2CONH2 will be detected in the ISM and found in carbonaceous chondrites.The results present new evidence for the third theory on the origin of amino acids on the early Earth.

关 键 词：H2NCH2C（OH）NH H2NCH2CONH2 interstellar medium amino acid origin hydrogen tunneling 

分 类 号：O621.143[理学—有机化学] P155.22[理学—化学]