Origin of reversal of stereoselectivity for [4+2] cycloaddition reaction between cyclopentadiene and methyl methacrylate in the presence of the chloroloaluminate ionic liquid (1-ethyl-3-methyl-imidazolium chloride): in silico studies

2014 ◽  
Vol 92 (9) ◽  
pp. 862-867 ◽  
Author(s):  
Debashis Sahu ◽  
Manoj K. Kesharwani ◽  
Bishwajit Ganguly
Keyword(s):  
Ionic Liquid ◽  
Hydrogen Bonding ◽  
Methyl Methacrylate ◽  
Ion Pairs ◽  
Cycloaddition Reaction ◽  
Imidazolium Chloride ◽  
Imidazolium Cation ◽  
Activation Barriers ◽  
Bonding Effect ◽  
In Silico Studies

The origin of stereoselectivity for [4+2] cycloaddition reaction of methyl methacrylate with cyclopentadiene was investigated with the B3LYP-D3(BJ)/6-31+G(d)//B3LYP/6-31+G(d) level of theory in the presence of the ionic liquid 1-ethyl-3-methyl-imidazolium chloride (EMI+Cl–) and its acidic chloroaluminate melt, 1-ethyl-3-methyl-imidazolium heptachlorodialuminate (EMI+Al2Cl7–). The reaction of methyl methacrylate with cyclopentadiene was examined in the gas phase to rationalize the effect of the ionic liquid ion pairs EMI+Cl– and EMI+Al2Cl7–. The DFT calculated results were found to be in good agreement with the experimentally observed results. The much-discussed hydrogen bonding effect of the imidazolium cation with the dienophile is less important to govern the stereoselectivity for the cycloaddition reaction. The atoms in molecules theory was used to examine the role of hydrogen bonding between the EMI+ cation and methyl methacrylate in the transition state geometries. The calculated activation barriers with the M062X/6-31+G(d)//B3LYP/6-31+G(d) and MP2/6-311+G(d,p)//B3LYP/6-31+G(d) levels of theory also predict the similar exo/endo-stereoselectivity trend for the cycloaddition reactions.

Elucidating structure–property relationships in imidazolium-based halide ionic liquids: crystal structures and thermal behavior

2020 ◽  
Vol 235 (8-9) ◽  
pp. 365-374
Author(s):  
Kai Richter ◽  
Katharina V. Dorn ◽  
Volodymyr Smetana ◽  
Anja-Verena Mudring
Keyword(s):  
Hydrogen Bonding ◽  
Ionic Liquids ◽  
Thermal Behavior ◽  
Crystal Engineering ◽  
Ionic Interactions ◽  
Structure Property ◽  
Hydrogen Atoms ◽  
Imidazolium Chloride ◽  
Imidazolium Cation ◽  
Oh Groups

AbstractA set of imidazolium-based ionic liquids (ILs), 1-(2-hydroxyethyl)-3-methylimidazolium chloride (1), 1,3-bis-(2-hydroxyethyl)-imidazolium chloride (2), and 1-butyl-2,3,4,5-tetramethylimidazolium bromide (3), has been synthesized and their structural and thermal behavior studied. Organic halides are well-known IL formers with imidazolium halides being the most prominent ones. Functionalization of the imidazolium cation by enhancing its hydrogen bonding capacity, i.e. through introduction of –OH groups or by diminishing it, i.e. through substitution of the ring hydrogen atoms by methyl groups is expected to change the inter-ionic interactions. Consequently, the solid-state structures of 1–3 have been characterized with means of single X-ray diffraction to shed light on preferential inter-ionic interactions for obtaining valuable information on anti-crystal engineering, i.e. designing ion combinations that favor a low melting point and exhibit a low tendency for crystallization. The study reveals that endowing IL forming ions with an enhanced hydrogen bonding capacity leads to a depression in melting points and kinetically hinders crystallization. This study provides hints towards new design concepts for IL design, similar to the common strategy of employing conformationally flexible ions.

Molecular structure, reorientational dynamics, and intermolecular interactions in the neat ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate

2004 ◽  
Vol 76 (1) ◽  
pp. 255-261 ◽  
Author(s):  
J. H. Antony ◽  
D. Mertens ◽  
Tobias Breitenstein ◽  
Andreas Dölle ◽  
P. Wasserscheid ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Hydrogen Bonding ◽  
Quantum Chemical Calculations ◽  
Quantum Chemical ◽  
Ion Pairs ◽  
Md Simulations ◽  
Liquid Structure ◽  
Distribution Functions ◽  
Reorientational Dynamics ◽  
Pair Distribution Functions

Results on the molecular and liquid structure and the reorientational dynamics are reported for the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]). In quantum-chemical calculations for [BMIM][PF6] in the gas phase, hydrogen bonding between the proton at carbon 2 in the aromatic ring and the fluorine atoms of the hexafluorophosphate anion was found. From the analysis of 13C relaxation data, the reorientational motions were evaluated, and the Vogel-Fulcher-Tammann and Arrhenius activation energies for the overall and internal reorientational motions, respectively, of the different 13C-1H vectors are given as well as correlation times at 300 K. By performing molecular dynamics (MD) simulations, pair distribution functions between moieties in the cation and the phosphorous atom in the anion were determined. The pair distribution function for the proton at carbon 2 exhibits a particular sharp and strong maximum indicating a strong interaction with the anion. The quantum-chemical calculations, the motional parameters, and the results from the MD simulations support the existence of hydrogen bonding and the formation of ion pairs in the ionic liquid.

Hydrogen bonding and π–π interactions in imidazolium-chloride ionic liquid clusters

2015 ◽  
Vol 17 (22) ◽  
pp. 14437-14453 ◽  
Author(s):  
Richard P. Matthews ◽  
Tom Welton ◽  
Patricia A. Hunt
Keyword(s):  
Ionic Liquid ◽  
Hydrogen Bonding ◽  
Imidazolium Chloride ◽  
Π Interactions ◽  
Liquid Clusters

The importance of 1° and 2° hydrogen-bonding and anion–π+ interactions for ionic liquid structuring.

Stereospecific 1,3-H Transfer of Indenols Proceeds via Persistent Ion-Pairs Anchored By NH···Pi Interactions

2018 ◽  
Author(s):  
David Ascough ◽  
Fernanda Duarte ◽  
Robert Paton
Keyword(s):  
Computational Analysis ◽  
Ion Pairs ◽  
Ion Pair ◽  
Hydrogen Atom Transfer ◽  
Polar Solvents ◽  
Chirality Transfer ◽  
Activation Barriers ◽  
Sense And Avoid ◽  
Phase Dynamics ◽  
Pi Interactions

The base-catalyzed rearrangement of arylindenols is a rare example of a suprafacial [1,3]-hydrogen atom transfer. The mechanism has been proposed to proceed via sequential [1,5]-sigmatropic shifts, which occur in a selective sense and avoid an achiral intermediate. A computational analysis using quantum chemistry casts serious doubt on these suggestions: these pathways have enormous activation barriers and in constrast to what is observed experimentally, they overwhelmingly favor a racemic product. Instead we propose that a suprafacial [1,3]-prototopic shift occurs in a two-step deprotonation/reprotonation sequence. This mechanism is favored by 15 kcal mol<sup>-1</sup> over that previously proposed. Most importantly, this is also consistent with stereospecificity since reprotonation occurs rapidly on the same p-face. We have used explicitly-solvated molecular dynamics studies to study the persistence and condensed-phase dynamics of the intermediate ion-pair formed in this reaction. Chirality transfer is the result of a particularly resilient contact ion-pair, held together by electrostatic attraction and a critical NH···p interaction which ensures that this species has an appreciable lifetime even in polar solvents such as DMSO and MeOH.

Dynamics of Ion Locking in Doubly Polymerized Ionic Liquids

2020 ◽  
Author(s):  
Swati Arora ◽  
Julisa Rozon ◽  
Jennifer Laaser
Keyword(s):  
Dielectric Constant ◽  
Ionic Liquid ◽  
Ionic Liquids ◽  
Ion Pairs ◽  
Polymer Chains ◽  
Ion Motion ◽  
Charged Species ◽  
Broadband Dielectric Spectroscopy ◽  
Covalently Linked ◽  
Insight Into

<div>In this work, we investigate the dynamics of ion motion in “doubly-polymerized” ionic liquids (DPILs) in which both charged species of an ionic liquid are covalently linked to the same polymer chains. Broadband dielectric spectroscopy is used to characterize these materials over a broad frequency and temperature range, and their behavior is compared to that of conventional “singly-polymerized” ionic liquids (SPILs) in which only one of the charged species is attached to the polymer chains. Polymerization of the DPIL decreases the bulk ionic conductivity by four orders of magnitude relative to both SPILs. The timescales for local ionic rearrangement are similarly found to be approximately four orders of magnitude slower in the DPILs than in the SPILs, and the DPILs also have a lower static dielectric constant. These results suggest that copolymerization of the ionic monomers affects ion motion on both the bulk and the local scales, with ion pairs serving to form strong physical crosslinks between the polymer chains. This study provides quantitative insight into the energetics and timescales of ion motion that drive the phenomenon of “ion locking” currently under investigation for new classes of organic electronics.</div>

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