OH surface groups

There is, of course, a mass of rather direct evidence on orientation at the liquid-vapor interface, much of which is at least implicit in this chapter and in Chapter IV. The methods of statistical mechanics are applicable to the calculation of surface orientation of assymmetric molecules, usually by introducing an angular dependence to the inter-molecular potential function (see Refs. 67, 68, 77 as examples). Widom has applied a mean-held approximation to a lattice model to predict the tendency of AB molecules to adsorb and orient perpendicular to the interface between phases of AA and BB [78]. In the case of water, a molecular dynamics calculation concluded that the surface dipole density corresponded to a tendency for surface-OH groups to point toward the vapor phase [79]. 

Chemisorbed water is considered to be present in the form of surface OH groups. 

Where HO—silica filler, inorganic solids carrying surface OH groups,... 

Molybdenum allyl complexes react with surface OH groups to produce catalysts active for olefin metathesis.34 35 Using silica as a support for the heterog-enization of Ti and Zr complexes for the polymerization of ethylene did not give clear results.36 In these cases, HY zeolite appeared to be a more suitable support. The comparable productivity of the zeolite-supported catalyst with... 

In principle, different surface sites can serve as anchoring sites but the surface OH groups are the most common anchoring groups on the oxide surfaces.225 These OH groups can take part in different reactions. For example, inorganic salts can react with the surface OH groups (Scheme 7.7).226... 

The reaction between the surface OH groups and SnCl4 leads to similar surface species (8 in Fig. 7.8).227... 

Anchored organometallic complexes of tungsten were prepared by the interaction of W(C4H7)4 with surface OH groups, and the resulting surface species play a role as precursors for the synthesis of different surface tungsten compounds (Scheme 7.11).231... 

The reaction of alkyllithium with surface OH groups produces reactive lithiated surface. For example, neopentyllithium reacts with the surface silanol groups of silica (Scheme 7.12).240... 

Spectroscopic data show that Sn remains tetracoordinated on the surface and one H atom of the terminal methyl is bonded to a surface OH group by hydrogen bonding (12 in Fig. 7.10). 

Bifunctional ligands containing alkoxy groups can be used for anchoring metal complexes to surface OH groups through a longer alkyl chain (Scheme 7.16).249-251... 

This probably has to do with the fact that DMF strongly hydrogen bonds to the surface -OH groups, which could inhibit the reaction with the methoxy-terminated PS chains. 

The number of surface OH groups can be determined by the method described by Van Veen et al. [136] according to the reaction... 

Most recently, a simple, mild, one-pot immobilization method was developed to attach the rigid rod-like helical polysilane, poly( -decyl-/-butylsilylene), via a siloxy linkage to hydrophilic quartz or mica substrate surfaces.28 195 Triethylamine was used as a catalyst to couple the Si-H and/or Si-OR termini of the dialkylpolysilane chains (which are generated during the course of Wurtz-type synthesis and workup)51,195 with the surface -OH groups. AFM, UV, and IR data were used to analyze the reactions. 

V A Lewis acid site is a surface site capable of receiving a pair of electrons from the adsorbate. A Lewis base is a site having a free pair of electrons (like an oxygen donor atom in a surface OH-group) that can be transferred to the adsorbate. 

In a similar way a sigma bond exerted by a functional surface OH-group to a metal ion causes a trans effect on the ligands bound to the metal ions (cf. Chapter 9.1). 

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