Hydroxyl-Reactive Chemical Reactions

It can be considered that the compounds produced through biosynthesis can be used as raw materials for the synthesis of useful plastics and materials in human life. Major plant components, such as saccharides and lignin, contain highly reactive hydroxyl groups, which can be used as reactive chemical reaction sites. As shown in Figure 1, it is possible to... 

The aminophenols are chemically reactive, undergoing reactions involving both the aromatic amino group and the phenoHc hydroxyl moiety, as weU as substitution on the benzene ring. Oxidation leads to the formation of highly colored polymeric quinoid stmctures. 2-Aminophenol undergoes a variety of cyclization reactions. 

Surface Modification of Cellulose and PVA Films. Cellulose, as well as PVA,is known to be a typical non-ionic, hydrophilic polymer possessing hydroxyl groups. As this group has a high reactivity,chemical modification of these polymers is relatively easy and, in fact, has been the subject of extensive research. However, so far as we know, no work has been reported concerned with reactions occurring only at the surface of films or fibers from these polymers. 

The interaction of the polymer with the filler is promoted by the presence of reactive functionality in the polymer, capable of chemical reaction or hydrogen bonding with the functionality, generally hydroxyl, on the surface of the filler. Thus, carboxyl-containing polymers, e.g. ethylene-acrylic acid copolymers and maleic anhydride- and acrylic acid-grafted polyethylene and polypropylene interact readily with fillers. 

The curing process of epoxies is mainly dependent on the reactivity characteristics, the structure, and the functional group of resin [61,65], The basic chemical reactions, catalyzed by hydroxyl group (OH), between the epoxide group and the curing agent are [194] ... 

As indicated in Fig. 16.2, in addition to energy transfer, chemical reactions of excited UCs ( UC, 3UC ) may lead to the formation of other reactive oxygen species (ROS) that may react with organic pollutants. Such ROS include DOM-derived oxyl- and peroxyl radicals (RO , ROO ), superoxide radical anions (02 ) that may be further reduced to H202, and hydroxyl radicals (HO ). In the case of HO , however, DOM is a net sink rather than a source. Finally, some of the 3UC may react directly with certain more easily oxidizable pollutants (see below). 

Cyclodextrins can stabilize some unstable molecules against the effects of light, heat and oxidation. Association of the molecule or a portion of the guest molecule with the walls of the cavity of the cyclodextrin or hydroxyl groups on the rims of the cyclodextrin can result in increased activation energy required in order to cause a chemical reaction to occur. The cavity of the cyclodextrin is a finite space. If the space is filled, other molecules cannot enter the cavity to react with the included molecule. Some steric hindrance can also be provided to included molecules to prevent reactive molecules from approaching the reactive sites of the guest molecule. 

Most of the research in the area of chemical modification of wood was conducted for improving either its dimensional stability or its biological resistance. Wood is made up primarily of cellulose, hemicellulose, and lignin. Originally, chemical modification of wood was a chemical reaction between some reactive part of a wood component and a simple chemical reagent to form a covalent bond between the two [1]. The most abundant reactive sites in wood are the hydroxyl groups. The major important types of covalent bonds formed by chemical modification of wood are ethers and esters. The treated wood must still possess the desirable properties of wood. Past research work on the chemical modification of wood was reviewed extensively in 1975 [1] and 1984 [2] by Rowell. 

If hydroxyl reactivity is selected as the preferred modification site, the chemical must contain functional groups that will react with the hydroxyl groups of the lignocellulosic components. This may seem obvious but there are several failed reaction systems in the literature using a chemical that could not react with a hydroxyl group. 

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