Surface hydroxyl groups chemical transformations

Transformation of triazines is primarily the result of degradation caused by microorganisms. However, triazines are also subject to a slow chemical degradation process known as hydrolysis. Chemical hydrolysis of atrazine, for example, is a process where the chlorine atom is removed from the atrazine molecule and replaced with a hydroxyl (OH) group. Chemical hydrolysis is relatively fast in acidic and alkaline soils, but it is relatively slow in neutral soils. In neutral soils, the rate of chemical hydrolysis of triazines increases when the triazine is adsorbed on the surfaces of soil particles. Hydroxytriazines, the products of chemical hydrolysis, are very strongly held by soil surfaces and hence move very slowly in soils. The hydroxytriazines have no biological activity. 

The possibility of manipulating thiol-derivatized gold nanoparticles as simple chemical entities was demonstrated by (partial) esterification of the surfece-bound hydroxyl groups of /7-meicaptophenol-functionalized nanoparticles. Further transformations of the functionahties inserted on the surface of nanoparticles can be performed under reaction conditions similar to those employed in conventional oiganic synthesis. 

The second type of surface treatment is in principle an improving of the chemical reactivity of the substrates by chemical or physical treatment methods. All the systems known lead to oxidizing effects of the nonpolar substrate and create carbonyl, carboxyl and hydroxyl groups at the surface which are polar and partly chemically reactive. The existence of these groups can be measured for example by Fourier transform infrared (FTIR) spectroscopy using the attenuated total reflexion (ATR) technique. 

On the other side, starch nanocrystals surface can be chemically modified. These modifications consist in transforming the polar hydroxyl group sitting at the surface of starch nanocrystals into moieties capable of enhancing interactions with nonpolar polymers (Label et al. 2007 Garcia et al. 2012). 

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