کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
443597 692739 2009 7 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Determination of local effects for chloroaluminate ionic liquids on Diels–Alder reactions
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی تئوریک و عملی
پیش نمایش صفحه اول مقاله
Determination of local effects for chloroaluminate ionic liquids on Diels–Alder reactions
چکیده انگلیسی

Room temperature ionic liquids are an exciting class of solvents that have the potential to accelerate and control a vast range of reactions. The Diels–Alder reaction, paradigm in organic synthesis, highlights the advantages provided by ionic liquids as the reaction between cyclopentadiene and methyl acrylate in 1-ethyl-3-methylimidazolium tetrachloroaluminate and heptachlorodialuminate [EMIM][AlCl4] and [EMIM][Al2Cl7], respectively, has been reported to react with rates over 200 times faster and endo selectivity 10 times greater than commonly used reaction conditions. Density functional theory (DFT) calculations at the B3LYP/6-311+G(2d,p) theory level have been employed to determine the origin of the reported rate accelerations. The DFT simulations find that specific hydrogen bonding between the ionic liquid cations and the dienophile at the transition state is primarily responsible, however, the rate of reaction was found to be moderated by the solvent's hydrogen bond accepting ability (anion effect). Different anion-to-cation ratios were tested and a 1:1 ratio was determined to give the best agreement with experimental observations. The computed DFT activation barriers were within reasonable agreement of the reported rates, however it is clear that a full microenvironment featuring hundreds of ions is necessary for proper computational treatment of the solvent effects delivered by the ionic liquids.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Molecular Graphics and Modelling - Volume 28, Issue 2, September 2009, Pages 95–101
نویسندگان
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