Infrared and Raman study of the interaction between methyl acetate and phenol derivatives

Vanderheyden, L.; Zeegers‐Huyskens, Th.

doi:10.1016/0167-7322(83)80003-8

Cited by 23 publications

(3 citation statements)

References 15 publications

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“…Since the association equilibria as extracted from the NMR chemical shift may be biased by a substrate induced variation of the bulk properties of the solvent, 24 in particular for weak variation of the chemical shift (see 2CF-DPTU and 0CF-DPTU), 25 we use IR spectroscopy as an independent method to detect association. 26 In general, the NH stretching vibrations of the thiourea group are very sensitive to molecular associations, as the N-H stretching markedly red-shifts upon hydrogen-bond formation. 27 In Fig.…”

Section: Association Equilibria From Ft-ir Spectroscopymentioning

confidence: 99%

CF3-groups critically enhance the binding of thiourea catalysts to ketones – a NMR and FT-IR study

Ehrhard

Jäger

Malm

et al. 2019

Journal of Molecular Liquids

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Substituted phenylthioureas have been established as efficient organocatalysts and substituents containing electron withdrawing CF 3 groups have been shown to enhance catalytic efficiency. The effect of the CF 3 groups on binding of catalysts to substrates in solution has however remained elusive. Here, we report on the effect of CF 3 substituted diphenylthioureas on the association with the substrate 1,3-diphenyl-2propenone in solution by using a combination of nuclear magnetic resonance (NMR) and Fourier-transform infrared (FT-IR) spectroscopy. We use the ensemble-averaged chemical shift of the thiourea proton as function of substrate concentration to determine the association constants between catalyst and substrate. To experimentally discriminate between free and bound catalyst we use infrared absorption spectra, which show a red-shift of thiourea's N-H stretching vibration upon association with the substrate. With both methods, we find the association constant K to increase from ~1 L/mol to ~20 L/mol with increasing number of CF 3 substituents. This enhanced binding can explain the increased reaction rates observed for CF 3 substituted diphenylthiourea catalysts. For the efficient catalyst containing four CF 3groups (Schreiner's catalyst), the strongest association is observed in toluene as a solvent, while the binding strength is somewhat weaker in dichloromethane, and association to the substrate is not detectable in acetonitrile. Our results thus demonstrate that even weak association between the thiourea catalysts and the ketone can facilitate efficient catalytic conversion. However, the association with the ketone substrates is very susceptible to competing interactions with the solvent.

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Section: Association Equilibria From Ft-ir Spectroscopymentioning

confidence: 99%

CF3-groups critically enhance the binding of thiourea catalysts to ketones – a NMR and FT-IR study

Ehrhard

Jäger

Malm

et al. 2019

Journal of Molecular Liquids

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“…Comparison of these data shows that the formation constants of the DPG complexes are higher than those reported for complexes involving the same proton donors and aliphatic esters; for the complex between 3,5-diCl phenol and methylacetate the K value is about 4 0 L m o l l (23) and for the complex between the same ester and pyrrole a K value of 1.3 has been reported in the literature (24). At this stage of the discussion.…”

Section: Results and Discussion Interaction With H Y D R O Q Derivatimentioning

confidence: 79%

“…These two absorptions were observed for the hydroxylic proton donors and the observed wavenumbers depend on their acidity (Table 3). for all the complexes) and by the shift of the uc-, band to higher frequencies (AucPo = + 13-15 cm-'); such behaviour is typical for hydrogen bonds formed on an ester group (23). The second band is assigned to complexes formed on the imino nitrogen atom.…”

Section: Results and Discussion Interaction With H Y D R O Q Derivatimentioning

confidence: 99%

An infrared study of the interaction between ethyl N-(diphenylmethylene)glycinate with proton donors: comparison with N-benzylidenemethylamine

Ruysen¹,

Zeegers‐Huyskens²

1986

Can. J. Chem.

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MARLEEN RUYSEN and T H~R~S EZEEGERS-HCYSKENS. Can. J. Chem. 64, 2305(1986.The interaction between ethyl N-(dipheny1methylene)gylcinate (DPG) and hydroxy proton donors or pyrrole has been investigated by ir spectrometry. The equilibrium constants, enthalpies, and entropies of complex formation have been determined in carbon tetrachloride solution and compared with the data obtained for the complexes involving N-benzylidenemethylamine and the same proton donors. The ir spectra studied mainly in the V O H , V C = N , VC=,, and uc-, regions suggest that hydrogen bond formation occurs at the N atom of the imino group and at the 0 atom of the carbonyl group. The results are discussed in terms of the basicity at the two acceptor sites and of the accessibility of the lone pair of electrons. The ir spectra of the solid adduct of DPG with HCI show that protonation takes place on the N atom. The protonated structure is possibly stabilized by an intramolecular hydrogen bond.

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Absolute Raman Intensities of the Carbonyl Stretching Band in Para Substituted Methyl Benzoates

Vanderheyden

Zeegers‐Huyskens

1989

Ber Bunsenges Phys Chem

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The absolute Raman intensities of the vc=0 band of para substituted methyl benzoates have been measured in CCl4 solution at different excitation frequencies. The intensities depend on a preresonance Raman effect (PRRE) and are correlated with theoretical expressions which describe the dispersion of the Raman intensity as a function of the excitation frequency and the experimental UV frequencies of the compounds, in particular the π→π*1La band. ‐ The Raman intensities free from PRRE are deduced by extrapolating the experimental values to a zero excitation frequency. These extrapolated intensities depend on the electron donating character of the substituents and on the extent of the conjugated system. ‐ The depolarization ratio of the νc=0 band in methyl benzoates increases with the excitation energies, this ratio is higher for the para substituted derivatives.

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Infrared and Raman study of the interaction between methyl acetate and phenol derivatives

Cited by 23 publications

References 15 publications

CF3-groups critically enhance the binding of thiourea catalysts to ketones – a NMR and FT-IR study

CF3-groups critically enhance the binding of thiourea catalysts to ketones – a NMR and FT-IR study

An infrared study of the interaction between ethyl N-(diphenylmethylene)glycinate with proton donors: comparison with N-benzylidenemethylamine

Absolute Raman Intensities of the Carbonyl Stretching Band in Para Substituted Methyl Benzoates

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