Spectroscopic Evidence of Hydrogen Bonds: Aniline and Some Substituted Phenols

Both inter- and intra-molecular hydrogen bonding in certain substituted phenols was studied by determining the effect of the bonding on the OH fundamental occurring in the region of 3μ. For m- and o-nitro-phenols, complex formation with certain oxygenated solvents was studied. The vibrational band of the NH2 aniline group was found to shift to wave-lengths shorter by 0.07μ upon dilution of aniline in benzene solution. Association of the aniline in the liquid state through very weak hydrogen bonds is proposed as an explanation of this shift. Similar evidence is offered for the formation of very weak hydrogen bonds between aniline and the solvents n-butyl and isopropyl ethers.