n-Hexanol association in cyclohexane studied by NMR and NIR spectroscopies

Microheterogeneity in binary mixtures of aliphatic alcohols and alkanes: ATR-IR/NIR spectroscopic and chemometric studies

“…Though the literature on self-association of alcohols in nonpolar solvents is very rich it does not present a uniform picture. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Fletcher and Heller postulated the presence of monomers as well as the linear and cyclic tetramers of 1-octanol and 1-butanol in n-decane solutions but they did not observe the dimers. 1 In contrast, Asprion et al assumed that most of alcohols in n-hexane exist in equilibrium between the monomers, dimers and oligomers (mostly pentamers).…”

“…Flores et al studied 1-hexanol association in cyclohexane by using NMR and NIR spectroscopies. 12 The authors concluded that the structure of the mixture depends on its composition. At low 1-hexanol mole fraction (X < 0.05) dominates dispersion interactions and the molecules of alcohols exist mainly as monomers.…”

Nonpolar Water Clusters: Proton Nuclear Magnetic Resonance Spectroscopic Evidence for Transformation from Polar Water to Nonpolar Water Clusters in Liquid State

“…At this temperature, rapid molecular motions inhibit the aggregation of n-hexanol and water. 22,24 Cooling significantly increases the chemical shift of the n-hexanol hydroxyl and water protons signals. In Figure 1b, the 1 H NMR signals from the hydroxyl protons and water are observed at ∼3 ppm, which indicates that hydrogen-bonded aggregates composed of n-hexanol and water exist at 243 K. The water clusters are observed at ∼6 ppm.…”

“…The gradual increase in the chemical shift of the Ha and W signals with decreasing temperature indicates the coexistence of dimers, trimers, and higher-order aggregates of n-hexanol and water. 22,24 The water clusters signal appears abruptly with a greatly elevated chemical shift (∼5.5 ppm) at ∼300 K in Figures 2a and 2b. The intensity of the water clusters signal is increasing with decreasing temperature accompanied by a decrease of the signals of water with n-hexanol (Figure 2a) or water without n-hexanol (Figure 2b).…”

“…The large intensity of the solvent signal can be reduced by use of a deuterated solvent. The environmental sensitivity of the chemical shift and a good signal-to-noise ratio are advantages of 1 H NMR over other spectroscopic techniques. − Recently, we have preliminarily reported the existence of long-lived water clusters in hydrophobic solvents . The specific number of molecules in a small water cluster has been determined experimentally from the NMR chemical shift and by theoretical calculations.…”