Hydrogen bonding phenols

Phenol Hydrogen bond partner Method of smdy Reference... 

O chemical shifts of phenols hydrogen bonded to heteroaromatic nitrogens in systems like o-hydroxypyridines or similar compounds with one or more nitrogens or hydroxy groups show OH chemical shifts that are very similar (94-97 ppm), with the exception of a para-substituted methoxy derivative (90 ppm) , but this can be ascribed to a simple substituent effect (see above). 

Third, the AH" and AS" valnes of many hydrogen-bonded complexes have been obtained from van t Hoff plots where the temperature range AT was nsnally too small. Enthalpies and entropies calcnlated with AT = 10° for the complexes of 4-nitrophenol with amines are inevitably less reliable than those calcnlated with AT = 78° for snbstitnted phenols hydrogen-bonded to dhnethylacetamide or with AT = 57° for snb-stimted phenols complexed with diphenyl snlfoxide , simply becanse the error in AH" is inversely related to AT. 

The dipole moments wctc related to hydrogen bond strength and to the ability of the proton acceptors (compounds with phosphoryl and carbonyl groups) to associate with phenol. Hydrogen bonded complexes of pyridines, quinolines and acridine with phenol are studied, in carbon tetrachloride, by dipole moment measures . Dipole moments of the complexes were related to the ability of the acceptors to associate with phenol and with their basicity. Hydrogen bonds may either reinforce the dipole moments of the resultant of the group moments or may oppose the dipole moment direction, depending on the nature of the acceptor. 

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