Surfaces, bond types hydroxyl groups

Figure 1.9. Surface hydroxyl groups on goethite singly (A-type), triply (B-type), and doubly (C-type) coordinated to Fe(III), along with Lewis acid site hydroxyls. The drawing on the right shows an inner-sphere surface complex with HP04 at the A-type hydroxyl group. The dashed lines indicate hydrogen bonds.

These oxazolines have cationic surface-active properties and are emulsifying agents of the water-in-oil type. They ate acid acceptors and, in some cases, corrosion inhibitors (see Corrosion). Reaction to oxazoline also is useful as a tool for determination of double-bond location in fatty acids (2), or for use as a protective group in synthesis (3). The oxazolines from AEPD and TRIS AMINO contain hydroxyl groups that can be esterified easily, giving waxes (qv) with saturated acids and drying oils (qv) with unsaturated acids. 

Alcohols react with surface hydroxyl group to form C-O-Si bonds. Because this type of bond is not very stable, trialkoxysilanes are preferred for anchoring. Exceptions to this rule are polyhydric alcohols, such as tris(hydroxymethyl)phos-phine [86], which forms multiple bonds with the surface. 

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