Esterification, of hydroxyl groups

Etherification and esterification of hydroxyl groups produce derivatives, some of which are produced commercially. Derivatives may also be obtained by graft polymerization wherein free radicals, initiated on the starch backbone by ceric ion or irradiation, react with monomers such as vinyl or acrylyl derivatives. A number of such copolymers have been prepared and evaluated in extmsion processing (49). A starch—acrylonitrile graft copolymer has been patented (50) which rapidly absorbs many hundred times its weight in water and has potential appHcations in disposable diapers and medical suppHes. 

Polyimides based on 2,6-diamino-p-cresol were acylated with acryloylchloride [71, 72] to impart photosensitivity to these polymers. The acylation was carried out in accordance with Scheme 5.12. The extent of esterification of hydroxyl groups, as determined by H-NMR spectroscopy, ranged from 60 to 40% for various polyimides (Table 5.14). 

Nitration of pentaerythritol benzoate causes both esterification of hydroxyl groups with nitric acid, and a simultaneous nitration of the benzene ring to... 

The mechanism of acylation may be related to that of esterification of hydroxyl groups. 

Polymeric herbicides were prepared with 2,4-D and CMPA covalently or ionically bound to oligoethylenoxylated polystyrene resins at different degrees of crosslinking. These adducts were formed by ion exchange, by nucleophilic displacement on chlo-romethyl groups, and by esterification of hydroxyl groups (Scheme 3.3) [127]. Herbicide release from polymer beads loaded with herbicide was monitored in aqueous solutions buffered at pH 4,7, and 9. For covalently bound herbicides, a release of... 

When acyl groups are introduced into carbohydrates by the esterification of hydroxyl groups, some degree of reciprocal relation should exist between the extent of esterification and the intensity of the periodic acid - Schiff reaction. Whenever the hydroxyl groups are sufficiently numerous, partial esterification may take place without any great decrease in the relative... 

Fischer esterification of hydroxyl groups with simultaneous hydrolysis of amorphous cellulose chains using organic acids, such as acetic and butyric acid, mixed with hydrochloric acid to extract CNs has become a viable one-pot reaction methodology that allows isolation of functionalized CNs in a single-step process [25, 26]. Figure 11.4 schematically illustrates the reaction during the process of extraction and... 

Surprisingly little work has been done on the biosynthesis of bi- and trithiophenes. The steps involved in the formation of such plant components start with the synthesis of the carbon skeleton, introduce sulfur atoms which are then incorporated into thiophene rings, and finish with minor side-chain adjustments. These may include reduction, oxidation, formation of epoxides, conversion of the latter into diols, esterification of hydroxyl groups, loss of carbon atoms, etc. 

Treating cellulose fibers with sulfuric acid involves esterification of hydroxyl groups by sulfate ions (Yao, 1999). Introduction of sulfate groups along the surface of the crystallites will result in a negative charge of the surface. This anionic stabilization via the attraction/repulsion forces of the electrical double layers at the crystallites is probably the reason for the stability of the colloidal suspensions of flie crystallites (Marchessault et al., 1961). The stable aqueous nanocellulose suspension is shown in Figure 1.1(a). 

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