Determination of alcohols in mixtures by 19F NMR spectroscopy using hexefluoroacetone reagent

Abstract

The determination of alcohols by 19F NMR spectroscopy making use of their reaction with hexafluoroacetone giving rise to hemiacetals was studied on butanols. The calibration curve method and the internal standard method were used and the results were mutually compared. The effects of some experimental conditions, viz. the sample preparation procedure, concentration, spectrometer setting, and electronic integration, were investigated; the conditions, particularly the concentrations, proved to have a statistically significant effect on the results of determination. For the internal standard method, the standard deviation was 0.061 in the concentration region 0.032-0.74 mol l-1. The method was applied to a determination of alcohols in the distillation residue from an oxo synthesis.

Unexpected Composition Dependence of the First Sharp Diffraction Peak in an Alcohol–Aldehyde Liquid Mixture:n‐Pentanol and Pentanal

“…Hemiacetals cannot be separated from such liquid mixtures (containing an alcohol and an aldehyde only) − their presence may only be noticed indirectly (e.g., by spectroscopic methods, such as NMR) . For a proper detection of hemiacetals, it seems best to use fluorinated compounds and 19 F NMR, or separate the hemiacetal fraction in the solid phase and apply solid state magic angle spinning (MAS) NMR . Conditions in the present investigation do not make it possible to apply the techniques just mentioned …”

“…For a proper detection of hemiacetals, it seems best to use fluorinated compounds and 19 F NMR, or separate the hemiacetal fraction in the solid phase and apply solid state magic angle spinning (MAS) NMR . Conditions in the present investigation do not make it possible to apply the techniques just mentioned …”