Equilibrium Acidities of Superacids

Kütt, Agnes; Rodima, Toomas; Saame, Jaan; Raamat, Elin; Mäemets, Vahur; Kaljurand, Ivari; Koppel, Ilmar A.; Garlyauskayte, Romute Yu.; Yagupolskii, Yurii L.; Yagupol’skii, L. M.; Bernhardt, Eduard; Willner, Helge; Leito, Ivo

doi:10.1021/jo101409p

Cited by 249 publications

(101 citation statements)

References 40 publications

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“…As a measure of the acid strength of the acids, their pK a values determined in acetonitrile (MeCN) were used, as reported in the literature. [48][49][50][51] Although the reaction mixture and MeCN are very different in nature ( phenol, the major component in the reaction media, is strongly protic, while MeCN is aprotic), and the media has a strong influence on the acidity, 48 In Fig. 5a, an obvious correlation between the p,p′ : o,p′ isomer ratio of the bisphenols at 55% 2,3-PD conversion and the pK a (MeCN) value of the acids is noticed.…”

Section: Influence Of the Catalyst And Its Acid Strength On The Regiomentioning

confidence: 98%

Regioselective synthesis of renewable bisphenols from 2,3-pentanedione and their application as plasticizers

et al. 2014

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Pentanedione (2,3-PD), a bio-based chemical derived from lactic acid, has the potential to serve as a precursor for the synthesis of novel bisphenols. We developed a solvent-free catalytic strategy for the condensation of phenol with 2,3-PD by using acid catalysts at temperatures ranging from 323 to 373 K.Various soluble and solid acids exhibit high activity, while a high chemoselectivity to bisphenol requires a high phenol to 2,3-PD molar ratio. Bisphenol yields as high as 84% are for instance reported in an excess of phenol in the presence of Nafion NR50. Recycling of the Nafion catalyst after washing with ethanol at room temperature is demonstrated. The regioselectivity in the bisphenol fraction is influenced by the acid strength. A clear trend is presented in which the regioselectivity towards the desired p,p'-isomers increases with increasing acid strength, showing p,p'/o,p'-isomer ratios as high as 100. A tentative mechanism is discussed based on the ionic versus non-ionic pathway. The purified 2,3-PD-derived p,p'-bisphenols are assessed as plasticizers for polyethylene terephthalate (PET), showing promising properties similar to that of the reference bisphenol A, but with a broader processing window due to the lower melting point and higher thermal stability under an inert atmosphere.

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Section: Influence Of the Catalyst And Its Acid Strength On The Regiomentioning

confidence: 98%

Regioselective synthesis of renewable bisphenols from 2,3-pentanedione and their application as plasticizers

et al. 2014

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“…Protons in the neighborhood of the triflate anion [121] should experience different shielding than what solvated protons far away from the anion experience. One expects in this case an overall up-field effect [122].…”

Section: Hydrated Proton Clusters Distribution In Acetonitrilementioning

confidence: 99%

Probing Small Protonated Water Clusters in Acetonitrile Solutions by ¹H NMR

Sigalov

Kalish

Carmeli

et al. 2013

Zeitschrift Für Physikalische Chemie

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Protonated Water Clusters / Eigen Cation / Zundel Cation / 1 H NMRIn a previous publication by Kalish et al. (J. Phys. Chem. A 115 (2011) 4063) the existence of well defined small protonated water clusters in acetonitrile has been established by IR spectroscopy. Here we report on a 1 H NMR study of triflic acid, CF 3 SO 3 H, in acetonitrile-water solutions. Using NMR we are able to corroborate the general solvation scheme we have proposed for the hydrated proton in acetonitrile as a function of the molar ratio between the strong mineral acid and water, n = [H 2 O]/[acid]. According to this scheme, backed now by both IR absorption spectroscopy and NMR measurements, the very strong triflic acid completely dissociates in acetonitrile/water solutions to yield the aqueous proton and the triflate anion when n > 1. Furthermore, increasing n results in the proton solvated in increasingly larger water clusters formed within the acetonitrile solution.Clearly distinguishable by NMR are the smallest protonated water clusters, the protonated water monomer, H + 3 O, and the protonated water dimer, H + 5 O 2 , which dominate the solution for n = 1,2,3. For larger n the NMR study indicates the gradual increase of the average protonated water cluster size as a function of n while the proton inner solvation core more closely retaining the characteristics of a deformed protonated water dimer, (H 2 O-H + · · ·OH 2 ) s than that of the protonated water monomer (H + 3 O) s .

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“…If we also allow a hydrogen‐bonding interaction for each of the two water molecules in the network of CH protons at the electropositive fac tris‐chelate sites (Figure 3 b), which collectively act as an H‐bond donor site comparable in strength to phenol,11, 19 we find that the encapsulated water molecules have, on average, 3.2 hydrogen‐bonding interactions each. Of these, the OH⋅⋅⋅F interactions with tetrafluoroborate are likely to be relatively weak given the poor basicity of tetrafluoroborate compared to water20 (HBF 4 is a stronger acid than H 3 O + , and the tetrafluoroborate anion is well known to be a much poorer donor to electropositive metal cations than H 2 O, despite its negative charge). Thus, we can consider 3.2 hydrogen‐bonding interactions per water molecule as an upper limit.…”

Section: Resultsmentioning

confidence: 99%

Binding of Hydrophobic Guests in a Coordination Cage Cavity is Driven by Liberation of “High‐Energy” Water

Metherell

Cullen

Williams

et al. 2017

Chemistry A European J

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The cavity of an M8L12 cubic coordination cage can accommodate a cluster of ten water molecules in which the average number of hydrogen bonds per water molecule is 0.5 H‐bonds less than it would be in the bulk solution. The presence of these “hydrogen‐bond frustrated” or “high‐energy” water molecules in the cavity results in the hydrophobic effect associated with guest binding being predominantly enthalpy‐based, as these water molecules can improve their hydrogen‐bonding environment on release. This contrasts with the classical form of the hydrophobic effect in which the favourable entropy change associated with release of ordered molecules from hydrophobic surfaces dominates. For several guests Van't Hoff plots showed that the free energy of binding in water is primarily enthalpy driven. For five homologous pairs of guests related by the presence or absence of a CH2 group, the incremental changes to ΔH and TΔS for guest binding—that is, ΔΔH and TΔΔS, the difference in contributions arising from the CH2 group—are consistently 5(±1) kJ mol−1 for ΔΔH and 0(±1) kJ mol−1 for TΔΔS. This systematic dominance of ΔH in the binding of hydrophobic guests is consistent with the view that guest binding is dominated by release of “high energy” water molecules into a more favourable solvation environment, as has been demonstrated recently for some members of the cucurbituril family.

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Equilibrium Acidities of Superacids

Cited by 249 publications

References 40 publications

Regioselective synthesis of renewable bisphenols from 2,3-pentanedione and their application as plasticizers

Regioselective synthesis of renewable bisphenols from 2,3-pentanedione and their application as plasticizers

Probing Small Protonated Water Clusters in Acetonitrile Solutions by ¹H NMR

Binding of Hydrophobic Guests in a Coordination Cage Cavity is Driven by Liberation of “High‐Energy” Water

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Equilibrium Acidities of Superacids

Cited by 249 publications

References 40 publications

Regioselective synthesis of renewable bisphenols from 2,3-pentanedione and their application as plasticizers

Regioselective synthesis of renewable bisphenols from 2,3-pentanedione and their application as plasticizers

Probing Small Protonated Water Clusters in Acetonitrile Solutions by 1H NMR

Binding of Hydrophobic Guests in a Coordination Cage Cavity is Driven by Liberation of “High‐Energy” Water

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Probing Small Protonated Water Clusters in Acetonitrile Solutions by ¹H NMR