Effect of ionic liquids in unimolecular solvolysis reactions involving carbocationic intermediates

Kochly, Elizabeth D.; Citrak, Susan C.; Gathondu, Nelius; Amberchan, Gabriella

doi:10.1016/j.tetlet.2014.10.145

Cited by 6 publications

(5 citation statements)

References 21 publications

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“…While these comparisons are of interest, no activation parameter data was determined, so the origins of the rate changes in terms of entropy and enthalpy of activation were not discussed. Further, no dependence of reaction outcome on the proportion of ionic liquid in the reaction mixture was considered; this has been shown to be significant in previous reports [4e,9a,k,n,p,r,14] …”

Section: Introductionmentioning

confidence: 99%

The effect of the structure of the cation of an ionic liquid on the rate of reaction at a phosphorus centre

Butler

Harper

2016

J of Physical Organic Chem

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The effect of a series of bis(trifluoromethanesulfonyl)imide-based ionic liquids containing different cations on the reaction of ethanol-d 6 with diethyl chlorophosphate was investigated. The addition of each of the salts increased the rate constant, with the extent of this increase being dependent on the mole fraction of the ionic liquid in the reaction mixture and, to a lesser extent, the nature of the cation; less bulky cations with ready access to the charged centres facilitated the greatest increases in the rate constant. Temperature-dependent kinetic analyses demonstrated that the rate enhancements were due to a decrease in the activation enthalpy offsetting a decrease in the activation entropy; this basis of the rate enhancement was consistent for all of the ionic liquids used and suggests stabilisation of the transition state of the process along with associated ordering of the solvent. Copyright

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Section: Introductionmentioning

confidence: 99%

The effect of the structure of the cation of an ionic liquid on the rate of reaction at a phosphorus centre

Butler

Harper

2016

J of Physical Organic Chem

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“…More aliphatic substitution creates a more electron-rich hydroxyl group, which will behave as a stronger H-bond acceptor and a weaker H-bond donor. It is also well understood that the increase in steric The data for IL methanol mixtures came from our previous study in which we investigated how differences in the α and β values of the ILs affected the product ratio [16]. This current study expands the dataset by including additional alcohol cosolvents to determine whether the effects previously described are consistent among other IL alcohol dual solvent systems.…”

Section: Resultsmentioning

confidence: 86%

“…Our preliminary studies have shown that increasing the mole fraction of IL in an IL:alcohol dual solvent system increases the favorability of the elimination pathway vs. nucleophilic attack [15,16]. It was observed that nearly all IL cosolvents caused an increase in the favorability of the elimination pathway.…”

Section: Resultsmentioning

confidence: 96%

“…Plots for the fifteen solvent systems are shown in Figure 2 Table 1 along with the Kamlet-Taft solvatochromic parameters for hydrogen bond donating and accepting ability, α and β, respectively [17]. The data for IL methanol mixtures came from our previous study in which we investigated how differences in the α and β values of the ILs affected the product ratio [16]. This current study expands the dataset by including additional alcohol cosolvents to determine whether the effects previously described are consistent among other IL alcohol dual solvent systems.…”

Section: Resultsmentioning

confidence: 99%

“…Looking at the difference between IL and alcohol α values gives an idea of the magnitude of this effect (i.e., how dramatically the α value decreases as more IL is added). This was explained in great detail in our previous paper [16]. For example, for a single IL, methanol cosolvent would have the most rapid decrease in α with increasing mole fraction IL (because methanol has the largest α), whereas isopropanol would have the most gradual (because isopropanol has the smallest α).…”

Section: Ionic Liquids With Varying α Valuesmentioning

confidence: 89%

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Unimolecular Solvolyses in Ionic Liquid: Alcohol Dual Solvent Systems

2016

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Abstract:A study was undertaken of the solvolysis of pivaloyl triflate in a variety of ionic liquid:alcohol solvent mixtures. The solvolysis is a k ∆ process (i.e., a process in which ionization occurs with rearrangement), and the resulting rearranged carbocation intermediate reacts with the alcohol cosolvent via two competing pathways: nucleophilic attack or elimination of a proton. Five different ionic liquids and three different alcohol cosolvents were investigated to give a total of fifteen dual solvent systems. 1 H-NMR analysis was used to determine relative amounts of elimination and substitution products. It was found, not surprisingly, that increasing the bulkiness of alcohol cosolvent led to increased elimination product. The change in the amount of elimination product with increasing ionic liquid concentration, however, varied greatly between ionic liquids. These differences correlate strongly, though not completely, to the Kamlet-Taft solvatochromic parameters of the hydrogen bond donating and accepting ability of the solvent systems. An additional factor playing into these differences is the bulkiness of the ionic liquid anion.

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The effect of the structure of the anion of an ionic liquid on the rate of reaction at a phosphorus centre

Butler

Harper

2018

J of Physical Organic Chem

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The effects of a series of 1‐butyl‐3‐methylimidazolium based ionic liquids containing different anions on the reaction of ethanol‐d6 with diethyl chlorophosphate were investigated. Addition of each of the salts considered resulted in an increase in the rate constant; the extent of this increase was dependent on the proportion of the ionic liquid in the reaction mixture. In contrast to previous studies, the ionic liquid effects continued to change at high proportions of these salts in the reaction mixture. Temperature‐dependent kinetic analyses were used to determine the microscopic origins of the rate constant enhancement. Correlations between the activation parameters and the coordinating ability of the anion of the ionic liquid (as measured using the Kamlet‐Taft βN parameter) suggest an additional interaction to those discussed previously. Importantly, these correlations suggest the opportunity for quantification of potential ionic liquid solvent effects in these systems.

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Effect of ionic liquids in unimolecular solvolysis reactions involving carbocationic intermediates

Cited by 6 publications

References 21 publications

The effect of the structure of the cation of an ionic liquid on the rate of reaction at a phosphorus centre

The effect of the structure of the cation of an ionic liquid on the rate of reaction at a phosphorus centre

Unimolecular Solvolyses in Ionic Liquid: Alcohol Dual Solvent Systems

The effect of the structure of the anion of an ionic liquid on the rate of reaction at a phosphorus centre

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