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1.r. spectral measurements were made to obtain frequency shifts ( AvOH) and integrated intensities (AOH) of the hydroxy stretching vibration for intramolecular hydrogen bonding in ortho-substituted phenols in dilute carbon tetrachloride solution. l H N.m.r. spectra were also measured to observe the chemical shift of the hydroxy proton.Two kinds of correlations were found between AvOH and AOH: one was a large increase of A,, with increasing nvOII, and the other a small increase of AOH. The former was found in phenols having a proton acceptor unconjugated with the benzene ring and the latter in those having a conjugated acceptor. The latter correlation was interpreted as resulting from a large delocalization effect of the OH bond electrons through the hydrogen bond system; this was supported by model calculations using the CND0/2 method to estimate&,.A linear correlation was also found between Avo, and As,,.An empirical equation linearly relating the hydrogen bond energy to AvOH is proposed. The calculated force constants, frequency shifts, and energies for the hydrogen bond systems were compared with the experimental data giving a fairly good result.

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