Health & Environmental Research Online (HERO)


Print Feedback Export to File
8722273 
Journal Article 
An enthalpic scale of hydrogen-bond basicity. 4. Carbon π bases, oxygen bases, and miscellaneous second-row, third-row, and fourth-row bases and a survey of the 4-fluorophenol affinity scale 
Laurence, C; Graton, J; Berthelot, M; Besseau, F; Le Questel, JY; Luçon, M; Ouvrard, C; Planchat, A; Renault, E 
2010 
Yes 
Journal of Organic Chemistry
ISSN: 0022-3263
EISSN: 1520-6904 
75 
12 
4105-4123 
English 
The thermodynamics of the O-HB hydrogen bond (HB) has been determined in CCl4 by FTIR spectrometry for a wide variety of carbon π bases, oxygen bases, and miscellaneous first- to fourth-row bases, using 4-fluorophenol as a reference hydrogen-bond donor (HBD). After inclusion of previously studied nitrogen, sulfur, and halogen bases, this 4-fluorophenol affinity scale contains 314 varied organic bases and ranges over 40 kJ mol-1. The 4-fluorophenol affinity scale in CCl4 is shown to be applicable to most HBDs in most media, provided a small family dependence is taken into account. The HB affinity orders are quantitatively established according to the atomic acceptor site or to its bearing functional group. A comprehensive survey of the influence of substituents on these affinity orders is then achieved, considering electronic and steric effects, as well as effects of vinylogy or iminology. Iminology is found to be more efficient than vinylogy for transmitting resonance effects. Steric effects are shown to be less important in HB affinity than in HB basicity since they mainly act on the HB entropy. The spatial proximity of two acceptor sites can favor complexation through three-center hydrogen bonds, leading to superhydrogen-bond bases on the affinity scale. 2010 American Chemical Society.