국내 최대 기계 및 로봇 연구정보

기술보고서

기술보고서 게시판 내용
타이틀	A Theoretical Investigation of the Plausibility of Reactions Between Ammonia and Carbonyl Species (Formaldehyde, Acetaldehyde, and Acetone) in Interstellar Ice Analogs at Ultracold Temperatures
저자	Chen, Lina;; Woon, David E.
Keyword	ACETALDEHYDE;; ACETONE;; AMMONIA;; CRYOCHEMISTRY;; EXTRATERRESTRIAL WATER;; FORMALDEHYDE;; ICE;; INTERSTELLAR CHEMISTRY;; INTERSTELLAR MATTER;; MOLECULAR CLOUDS;; PROTONS;; SOLVENTS;; SPECTROSCOPY
URL	http://dx.doi.org/10.1021/jp1103406
보고서번호	none
발행년도	2011
출처	NTRS (NASA Technical Report Server)
ABSTRACT	We have reexamined the reaction between formaldehyde and ammonia, which was previously studied by us and other workers in modestly sized cluster calculations. Larger model systems with up to 12H2O were employed, and reactions of two more carbonyl species, acetaldehyde and acetone, were also carried out. Calculations were performed at the B3LYP/6-31+G level with bulk solvent effects treated with a polarizable continuum model;; limited MP2/6-31+G calculations were also performed. We found that while the barrier for the concerted proton relay mechanism described in previous work remains modest, it is still prohibitively high for the reaction to occur under the ultracold conditions that prevail in dense interstellar clouds. However, a new pathway emerged in more realistic clusters that involves at least one barrierless step for two of the carbonyl species considered here: ammonia reacts with formaldehyde and acetaldehyde to form a partial charge transfer species in small clusters ƔH2O) and a protonated hydroxyamino intermediate species in large clusters ƙH2O, 12H2O); modest barriers that decrease sharply with cluster size are found for the analogous processes for the acetone-NH3 reaction. Furthermore, if a second ammonia replaces one of the water molecules in calculations in the 9H2O clusters, deprotonation can occur to yield the same neutral hydroxyamino species that is formed via the original concerted proton relay mechanism. In at least one position, deprotonation is barrierless when zero-point energy is included. In addition to describing the structures and energetics of the reactions between formaldehyde, acetaldehyde, and acetone with ammonia, we report spectroscopic predictions of the observable vibrational features that are expected to be present in ice mixtures of different composition.