NMR STUDIES OF HYDROGEN BONDING IN HINDERED PHENOLS
Abstract
Hydrogen bonding of the hindered phenols, 2-iso propylphenol, 2,6- diisopropylphenol, 2-t butylphenol, 2-methyl-6-t-butylphenol, and 2,6 di-t- butylphenol, were studied by observing the chemical shifts of -OH group protons. Room tem perature dilution shifts in C C14 of the phenolic -OH gives dimerization constants K of 1.7, 1.3, 1.0 < 0.05, and < 0.05, respectively, for the 5 phenols. Association constants K sub c for phenol-dioxane complexes were obtained from the phenolic -OH dilution shifts in 1,4-dioxane, em ploying general algebraic expressions. The K sub c's are in the same sequence as the K's but about ten-fold larger, consistent with the greater ease with which a smaller molecule approaches the phenolic -OH. Ethanolic and the phenolic -OH dilution shifts in ethanol-phenol solutions gave similar results, which were limited to a qualita tive interpretation by the relatively strong polymerization of the ethanol. Several lines of evidence, including the temperature dependence of the -OH shifts in a 1:1 equimolecular phenol ethanol mixture and the dilution shifts of the 1:1 mixture in carbon tetrachloride, indicate the stabler form of the complex has the phenolic H bonded to the ethanolic O.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 13, 1963
- Accession Number
- AD0410117
Entities
People
- B. G. Somers
- Herbert S. Gutowsky
Organizations
- University of Illinois Urbana–Champaign