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Partition coefficients and intramolecular hydrogen bonding. 1. The hydrogen‐bond basicity of intramolecular hydrogen‐bonded heteroatoms
Author(s) -
Berthelot Michel,
Laurence Christian,
Foucher Denis,
Taft Robert W.
Publication year - 1996
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199605)9:5<255::aid-poc779>3.0.co;2-g
Subject(s) - intramolecular force , chemistry , hydrogen bond , lone pair , heteroatom , low barrier hydrogen bond , photochemistry , stereochemistry , crystallography , ring (chemistry) , organic chemistry , molecule
Measurements were made in CCl 4 of the formation constant K HB of the 1:1 hydrogen‐bonded complexes between the reference donor 4‐fluorophenol and the intramolecular hydrogen‐bonded systems I (one lone pair on heteroatom Y, one intramolecular hydrogen bond: 8‐hydroxyquinaldine and 2‐(2‐hydroxyphenyl)benzoxazole); II: (two lone pairs, two intramolecular hydrogen bonds: 2,2′‐dihydroxybenzophenone and 1,8‐dihydroxyanthrone) and III (two lone pairs, one intramolecular hydrogen bond: tropolone, salicylic acid derivatives and guaiacol). The p K HB values and the structural vibrational studies show that system I has a non‐zero hydrogen‐bond basicity which is due to the oxygen atom. In system II the non‐zero basicity is explained by the two oxygens and the breaking of one intramolecular hydrogen bond. In the push‐pull system III (e.g. tropolone), in spite of the great decrease of the basicity of the free lone pair by the intramolecular hydrogen bond (e.g. compared with tropone), Y remains the major site for intermolecular association. However in guaiacol, a non push‐pull system III, the cooperativity effect makes the phenolic oxygen the major site.