May 5, 1952
0-H STRETCHING FREQUENCIES IN P H E N O L S [CONTRIBUTION FROM THE WESTERN
2297
AND CATECHOLS
REGIONAL RESEARCH LABORATORY ‘1
Correlation of 0-H Stretching Frequencies in Phenols and Catechols with Chemical Reactivities BY LLOYD L. INGRAHAM, JOSEPH CORSE, GLENF. BAILEYAND FREDSTITT The 0-H stretching frequencies have been studied for a series of substituted catechols and phenols. produced by substitution have been related to Hammett’s u values.
The frequency shifts
It will be shown in this paper that the frequency It has been shownza that substances capable of intramolecular hydrogen bonding such as catechol shifts produced by substitution in phenols and may exhibit two 0-H vibration frequencies, one catechols can also be related to Hammett’s u corresponding to a hydrogen bonded or “bound” values.4 hydroxyl and the other to the non-hydrogen bonded Experimental or “free” hydroxyl. The effects of ortho-substitMaterials.-The catechols used in this study have been uents which combine both steric and electronic described in a previous paper.* The phenols are all comeffects on the frequency of the bound hydroxyl mercially available. The m-cresol, p-chlorophenol, mabsorption have been extensively studiedzbby infra- ethylphenol were purified by distillation under reduced pressure. The hydroquinone monobenzyl ether, hydrored spectroscopy. However, little is known con- quinone monomethyl ether and p-hydroxybenzaldehyde cerning the electronic effects of substituents, per se, were crystallized from water and dried over phosphorus penapart from steric effects. By studying substituents toxide in vacuo. The m-aminophenol was crystallized from in other than the ortho position, steric effects can toluene. The other compounds were used without further purification. The solvents, carbon tetrachloride and tetrabe largely eliminated. Some of the needed spectro- chloroethylene, were distilled from phosphorus pentoxide scopic data for the evaluation of the electronic and used within three days after distillation. Absorption Spectra.-Dilute (
