Hydrogen Bonds with Varying Strengths

The H bond is basically an associative interaction that is much weaker than the ordinary covalent bond [la]. Lying between the weak vdW interaction and the strong covalent bond, the H bond spans a wide range of interaction strengths, which can differ by up to two orders of magnitude (0.2-40 kcal mol ) [3] depending on the type 

X-H- Y interaction Mostly covalent Mostly electrostatic Electrostatic 

Examples Gas-phase dimers Adds Gas-phase dimers 

Adapted from Ref. [Ic] with permission of Oxford University Press. Inc. 

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To investigate the effect of alcohol hydrogen-bond donor (HBD) strength in a systematic way, a series of modifiers possessing a common 4-teri-octylphenoxy ethanol core element were prepared, in which the properties of the substituent attached to the alcohol carbon atom were varied. These modifiers were evaluated with respect to both the cesium extraction strength they afforded when used in combination with BC6 and the HBD strength of the solvent as assessed using the solvatochromic parameter E. ... 

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