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 s stems were the weight centers of A-H stretching bands (v, cm-') and their integral absorption coefficients ( a , 10' cm mmol-') had been measured. The relationships between AH$$ and the parameters of the infrared absorption spectra [weight center shifts A v and the changes in the square roots of CI (Aa'/')] were analyzed. It was found that the dependence of AHAHiB on Aa'" consists of two nearly parallel straight lines: the first (-AH$$ = 12.0 + 0.4) corresponJtto water and the weak C-H and 0-H H-bond donors (chloroethylenes, acetylenes acetonitrile, nitromethane, chloroform, o,o'-di-tert-butylphenol); the second (-AH$$ = 12-1 A d z -4.2) corresponds to the stronger N-H and 0-H H-bond donors (N-methylaniline, pyrrole, alcohols, phenol, carbon acids). Non-linear dependences of A H c k t on Av were obtained for all C-H, N-H and 0-H H-bond donors except water [-AH%;: = 59.9 Av/(Av+ 674)l. Enthal ies of specific estimated by the above correlations with an accuracy of *3 to *6 kJmo1-I. These relationzips obtained for solutions of H-bond donors in pure bases differ from the well known dependences determined for the AH...B hydrogen bonding in carbon tetrachloride medium. considered for which the enthalpies of specific interaction due to hydrogen bonding AH.*.B (AHFL,., i Y kJmol-I), interaction for water obey another dependence [-AH2.:L72 = 28.