HYDROGEN-BONDING IN PURE BASE MEDIA - CORRELATIONS BETWEEN CALORIMETRIC AND INFRARED SPECTROSCOPIC DATA

The known correlations between calorimetric and IR spectroscopic data on hydrogen bonding were reinvestigated for hydrogen bond donors (AH) dissolved in pure bases (B). Ninety-five AH ... B systems were conside red for which the enthalpies of specific interaction due to hydrogen b onding AH ... B (Delta H-sp.int.(AH/B), kJ mol(-1)), the weight center s of A-H stretching bands (nu, cm(-1)) and their integral absorption c oefficients (a, 10(4) cm mmol(-1)) had been measured. The relationship s between Delta H-sp.int.(AH/B) and the parameters of the infrared abs orption spectra [weight center shifts Delta nu and the changes in the square roots of a (Delta a(1/2))] were analyzed. It was found that the dependence of Delta H-sp.int.(AH/B). On Delta a(1/2) consists of two nearly parallel straight lines: the first. (-Delta H-sp.int.(AH/B)=12. 0 Delta a(1/2)+0.4) corresponds to water and the weak C-H and O-H H-bo nd donors (chloroethylenes, acetylenes acetonitrile, nitromethane, chl oroform, o,o'-di-tert-butylphenol); the second (-Delta H-sp.int.(AH/B) =12.1 Delta a(1/2)-4.2) corresponds to the stronger N-H and O-H H-bond donors (N-methylaniline, pyrrole, alcohols, phenol, carbon acids), No n-linear dependences of Delta H-sp.int.(AH/B) on Delta nu were obtaine d for all C-H, interaction for water obey another dependence [-Delta H -sp.int.(H2O/B)/2=28.5 Delta nu/(Delta nu+269)]. The Delta H-sp.int.(A H/B) values can be estimated by the above correlations with an accurac y of +/-3 to +/-6 kJ mol(-1). These relationships obtained for solutio ns of H-bond donors in pure bases differ from the well known dependenc es determined for the AH ... B hydrogen bonding in carbon tetrachlorid e medium.