Silanol groups categories

Vibrational spectroscopy is a very powerful method for the study of hydroxyl species present. For zeolitic solids, these divide into three broad categories silanol groups, (SiO)3SiOH, hydroxyl groups bound to metal cations such as aluminium, AlOH, and bridging hydroxyls, Si-OH-Al. 

Two categories of silica are available as the basis for column materials. Type A silica has a lower concentration of silanol groups, while type B silica is fully hydroxylated. Type B silica, from hydrolysis of tetraalkoxysilanes, also contains less metal impurities. 

There are three distinct categories of silanol groups present on the surface of fused silica shown in Figure 3.17 ... 

Silanol types fall into three categories isolated, geminal (two -OH hydroxyl groups on the same silicon atom), and vicinal (on adjacent silicon atoms), as illustrated in Figure 9.6. 

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