Structural Properties of Pure Simple Alcohols from Ethanol, Propanol, Butanol, Pentanol, to Hexanol:  Comparing Monte Carlo Simulations with Experimental SAXS Data

Abstract

The primary liquid alcohols from ethanol to 1-hexanol were studied utilizing the configurational-bias Monte Carlo (MC) simulations of the modeled alcohols (transferable potential for phase equilibria-united atom model) and the small-angle X-ray scattering (SAXS) method. A novel approach for calculating the scattering intensities from the theoretically obtained MC data by utilizing the Debye equation and their further validation with experimental results was introduced. This procedure is important, since the common problem of how to initially separate the intra- and intermolecular contributions to the scattering when comparing the calculated and experimental data was successfully avoided. Nevertheless, the intra- and intermolecular contributions to the scattering were able to be investigated directly from the MC results. The most pretentious task of the procedure was the suppression of the MC box background scattering, which was solved by utilizing the averaging of the scattering intensities over the different box sizes. This method of the scattering intensity calculations enabled us to make a theoretical analog to the well-known small-angle neutron scattering contrast matching experiment that, in our case, nicely revealed the origin of the two alcohol scattering peaks in the SAXS regime of the scattering curves (0.3 A(-1)< q < 3 A(-1)). For the example of butanol, the outer alcohol scattering peaks at approximately 1.40 A(-1) were unambiguously ascribed to the correlations between the alcohol hydrocarbon tails described by the gCH(x)CH(x)(r) pair correlation function. Similarly, the inner alcohol scattering peaks that shift from approximately 0.8 to approximately 0.4 A(-1) with an increasing alkyl chain length of the alcohol molecule are mainly the consequence of the O-O correlations. These findings were tested on pentanol/water mixtures and further applied to the results of the structural investigations on the binary and ternary microemulsion systems of the nonionic surfactant Brij 35 (Tomsic, et al. J. Phys. Chem. B 2004, 108, 7021; Tomsic, et al. J. Colloid Interface Sci. 2006, 294, 194), which were in fact the actual motivation for this present study.

Near surface properties of mixtures of propylammonium nitrate with n-alkanols 1. Nanostructure

“…This structure is due to undulations in the native butanol layers confined between the surface and the tip; this interpretation is made primarily on the bases of the images for pure octanol and dodecanol, where the undulations are much clearer. The n-alkanols all form locally bilayered sheets in the bulk 10,54,55 which are aligned by the solid interface into smectic type layers. 56,57 The strength of attractive interactions between n-alkanol hydrocarbon chains increases with chain length meaning that nanostructure becomes better defined, as seen in Figure 2, where the undulations are clearest for dodecanol, then octanol, and quite unclear for butanol.…”

Charge ordering and scattering pre-peaks in ionic liquids and alcohols

“…The present study is essentially conducted by analysing the various atom-atom structure factors, as obtained by integral equations and computer simulations [20], and the total scattering function is rebuilt from these partial structure factors in order to be compared with that obtained through small or wide angle Xray scattering (SAXS or WAXS) experiments [5,6,21]. The second message of this paper is that radiation scattering experiments have appealing analogy with the BhatiaThornton (BT) transformation [22].…”

Size distribution of associated clusters in liquid alcohols: Interpretation of simulation results in the frame of SAFT approach

“…Infrared spectroscopy thus represents the most popular experimental methods to study the microscopic structure of the hydrogen bonded systems. [2][3][4][5][6][7][8] The neutron-or x-ray diffraction techniques [9][10][11][12][13] and the dielectric relaxation 14,15 can provide further information about the structure and dynamics of the hydrogen bonded systems. Indirect information about the hydrogen bonding can be deduced also from macroscopic properties (e.g., from the viscosity measurements or PvT behaviour and phase equilibrium data).…”

“…Several recent as well as classical studies were aimed to analyze the size and topology of associated species. 11,[25][26][27][28][29][30][31][32][33] The thermodynamic description of systems containing associating compounds represents a difficult task, especially in the case of mixtures of associating and non-associating components (e.g., alcohol-alcane) or systems which experience the cross-association despite the particular components alone do not associate (e.g., chloroform-acetone). 34 Among several approaches suggested to treat the behaviour of associating systems, the statistical association fluid theory (SAFT) of Wertheim [35][36][37][38] gained a prominent position and was incorporated into a family of equations of state.…”