A Polarized Infrared and X-Ray Study of Lysine-Vermiculite

Abstract--The adsorption and degradation on montmorillonite of s-triazine, the parent compound of a major group of triazine-based herbicides, were studied by Fourier-transform infrared spectroscopy. The original s-triazine appeared to hydrolyze with residual bound water in montmorillonite at 20"C to produce formamide, which formed an intercalate with the clay. A mechanism for the conversion of s-triazine to formamide was proposed which does not support earlier reports that formic acid and ammonia are the reaction products. The infrared spectrum of the formamide-Na-montmorillonite intercalate suggests that formamide reacted with the exchangeable Na cation and that the NH2 group hydrogen bonded with the clay. Assuming the intercalated formamide molecule to be planar, the molecular plane was found to be inclined at ~33 ~ with respect to the plane of the silicate sheet. C-N and C-O bonds were also found to be tilted at the same angle with respect to the clay surface. The proposed orientation is in good agreement with the measured value of d (001) for the formamide-Na-montmorillonite complex. The proposed model of the formamide-montmorillonite complex serves as a basis for comparison of other clay-amide complexes that are important in protein-clay interactions.

Section: Polarized Attenuated Total-reflectance Spectramentioning

confidence: 99%

Infrared Spectroscopic Study of the Formamide-Na-Montmorillonite Complex. Conversion of s-Triazine to Formamide

Nguyen

1986

“…The application of the polarized ATR technique has been shown to be useful for deducing the orientation of intercalated species on phyllosilicates, including cetylpyridinium cations, which have also been used for surface area measurements (Slade et al, 1978), amino acids (Raupach et al, 1975;Raupach and Janik, 1976), and paraquat (Raupach et al, 1979).…”

Section: Introductionmentioning

confidence: 99%

Fourier-Transform Infrared Study of Ethylene Glycol Monoethyl Ether Adsorbed on Montmorillonite: Implications for Surface Area Measurements of Clays

Nguyen

1987

Abstract-Infrared spectra of 2-ethoxyethanol (ethylene glycol monoethyl ether, EGME) adsorbed on Camontmorillonite were obtained using diffuse-reflectance infrared-Fourier-transform (DRIFT) and attenuated total-reflectance (ATR) spectroscopy. The molecular conformation of adsorbed EGME shows predominantly a gauche configuration for the CH2-CH2 linkage as originally present in the liquid. The orientation of the adsorbed EGME molecule in the interlamellar region of the clay was deduced from measurements of the polarized ATR spectra. The planar zig-zag skeleton of the molecule appears to have its long axis tilted at an angle of 44 ~ to the clay surface; the molecule is in van der Waals contact with both adjacent surfaces. Further, the plane of the skeleton of the molecule is tilted at an angle of 69 ~ to the clay surface. This orientation leads to estimates of the d-value of the clay-EGME complex and of the surface area occupied by each molecule. These values are in excellent agreement with independent measurements of both parameters. The full surface coverage on montmorillonite is represented by a single layer of tilted EGME molecules shared by two adjacent clay sheets; each molecule occupies a total surface area consisting of one portion (25.4 A2) on the lower surface of the interlayer plus another portion (14.8 ,~z) on the upper surface. The implication of this model for materials such as kaolinite, where adsorption takes place on the external surface only, is that on these materials each EGME molecule occupies 20/~2 at full surface coverage.

“…Previous work by Raupach et al (1975), Slade et al (1978), Slade and Raupach (1982), and Slade and Stone Copyright 9 1987, The Clay Minerals Society (1983) made use of superlattice reflections to characterize the well-ordered arrays formed when some organic species were intercalated into vermiculites. Particular note was taken that benzidine, 4-4'-diamino-trans-stilbene, and anilinium all gave rise to a single type of superlattice.…”

Section: Introductionmentioning

confidence: 99%

Crystal Structure of a Vermiculite-Anilinium Intercalate

Slade

Dean

Schultz

et al. 1987

Abstract--If anilinium ions are intercalated into Llano vermiculite, the stacking order of adjacent silicate layers is increased, resulting in a relatively sharp single crystal X-ray diffraction (XRD) pattern. The packing of intercalated organic members forms a superstructure and produces bonding from layer to layer which favors the stacking order. Superlattice reflections occur which, although sharp in the a'b* plane, are streaked along c*. Apparently there is little coherence between adjacent layers of ordered organic units.A three-dimensional set of XRD reflections for a triclinic sub-cell having the following lattice parameters was measured: a = 5.326(3), b = 9.264(4), c = 14.82(5) A, a = 90.31(7),/3 = 96.70(6), and 3' = 89.55(5) ~ In this unit cell (symmetry C1), ditrigonal cavities in adjacent silicate layers are approximately opposite. Differential Fourier analyses and least-squares refinements showed that the principal axes of the anilinium ions, i.e., N-C(1)-C(4), are nearly perpendicular to the silicate layers. The planes of the aromatic rings, however, are about +_ 30 ~ to X, neither parallel nor perpendicular to that direction, as indicated by earlier studies.Inorganic cations and water molecules are also present in the interlayer; the former and some of the latter occupy sites near the middle of the layer. Anilinium-rich and anilinium-poor domains coexist. In the latter, the cation-water system predominates and apparently conforms to the superstructure. Although the cation-water structure could not be uniquely established from the reflections produced by the subcell, possible positional coordinates were obtained. From structural data for the silicate layers, no evidence was found for long-range Si/A1 ordering in the tetrahedral sites.