Hydroxyl stretching vibration in 2,6-dimethyl- and 2,6-dichloro-4-substituted phenols

The infrared frequencies and apparent half band widths of the O—H stretching band of a series of 2,6-dimethyl-4-substituted phenols and a series of 2,6-dichloro-4-substituted phenols have been measured in carbon tetrachloride solution. The slopes of the Hammett plots for the frequencies and half band widths of both these series are compared with those calculated from published data for 2,6-di-t-butyl-4-substituted phenols and 3- or 4-substituted phenols. Significant differences are found in ρ obtained from the frequency data for the four series. The 2,6-dimethyl-4-substituted phenols, unlike the unhindered phenols, are found to parallel the 2,6-di-t-butyl-4-substituted phenols in having a negative ρ for the frequency data and a negative ρ for the half band width correlation. It is concluded that the negative ρ from the half band widths of 2,6-di-t-butyl-4-substituted phenols is primarily a result of electronic rather than steric factors.