Author(s):
Tonge, P.J. 
; Fausto, R. ; Carey, P.R.
Date: 1996
Persistent ID: http://hdl.handle.net/10316/17764
Origin: Estudo Geral - Universidade de Coimbra
Document details
FTIR studies of hydrogen bonding between α,β-unsaturated esters and alcohols
Description
The enthalpy (and entropy) of hydrogen bond formation has been measured between the ester carbonyl groups of the two α,β-unsaturated esters thienylacryloyl (TAOMe) and 5-methylthienylacryloyl (5MeTAOMe) methyl ester and the hydrogen bond donors ethanol, phenol and 3,5-dichlorophenol in CCl4. For the esters, the hydrogen bonding strengths were measured by quantitating the amount of bound and unbound donor, using the OH stretching region, as a function of temperature and applying the van't Hoff equation. The decrease in νCO of the ester carbonyl group upon hydrogen bond formation ΔνCO has also been measured and correlated with the enthalpy of hydrogen bond formation. A linear correlation is observed between the enthalpy of hydrogen bond formation −ΔH and ΔνCO, with −ΔH = 1.36ΔνCO − 16.1, where ΔH is measured in kJ mol−1 and Δν in cm−1. Comparison with data for other carbonyl acceptor compounds indicates that the carbonyl group of the above α,β-unsaturated esters is more readily polarized than the carbonyl group of saturated esters or ketones. The quantitative relationship between −ΔH and ΔνCO derived here has been used to determine the change in the enthalpy of hydrogen bond formation between substrate and enzyme groups in a series of acylserine proteases.
The enthalpy (and entropy) of hydrogen bond formation has been measured between the ester carbonyl groups of the two α,β-unsaturated esters thienylacryloyl (TAOMe) and 5-methylthienylacryloyl (5MeTAOMe) methyl ester and the hydrogen bond donors ethanol, phenol and 3,5-dichlorophenol in CCl4. For the esters, the hydrogen bonding strengths were measured by quantitating the amount of bound and unbound donor, using the OH stretching region, as a function of temperature and applying the van't Hoff equation. The decrease in νCO of the ester carbonyl group upon hydrogen bond formation ΔνCO has also been measured and correlated with the enthalpy of hydrogen bond formation. A linear correlation is observed between the enthalpy of hydrogen bond formation −ΔH and ΔνCO, with −ΔH = 1.36ΔνCO − 16.1, where ΔH is measured in kJ mol−1 and Δν in cm−1. Comparison with data for other carbonyl acceptor compounds indicates that the carbonyl group of the above α,β-unsaturated esters is more readily polarized than the carbonyl group of saturated esters or ketones. The quantitative relationship between −ΔH and ΔνCO derived here has been used to determine the change in the enthalpy of hydrogen bond formation between substrate and enzyme groups in a series of acylserine proteases.
Document Type
Article
Language English
Language English
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