Starch esterification

Derivatization Etherification Hydroxypropyl starch - Esterification with propylene oxide... 

Much helpful information on starch esterification methods and on the probable properties of starch esters may be obtained by examining similar reactions and esters in the cellulose field. This is because both starch and cellulose consist of polymerized glucose units capable of esterification to the triester stage, and because the superior ability of the cellulose esters to form plastics, films, fibers, and lacquers has promoted an accumulation of information on cellulose esters which far exceeds the present knowledge of starch esters. 

The limited solubility of starch and its modified products may affect the reversibility of many reactions. This may explain several, apparently unusual, reactions reported in starch chemistry. There are, for example, reports of starch esterification with sodium hydrogenphosphates, acylation of starch with acyl amides (which is equivalent to the transformation of an amide into an ester), and the formation of alkali-metal starchates upon treatment of starch with alkali (a reaction which fails for simple alcohols). A specific property of starch is its ability to form surface sorption and helical inclusion-complexes with many inorganic and organic guest molecules.4... 

Isobutylene/isoprene copolymer, brominated food starch esterification, modified Vinyl acetate... 

Hanna MA, Fang Q. 2002. Starch esterification by reactive extrusion. Agro-Food-Industry Hi-Tech 13 33-36. 

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. 

Sorbitol is the most important higher polyol used in direct esterification of fatty acids. Esters of sorbitans and sorbitans modified with ethylene oxide are extensively used as surface-active agents. Interesteritication of fatty acid methyl esters with sucrose yields biodegradable detergents, and with starch yields thermoplastic polymers (36). 

Dzulkefly, K Koon, S. Y. Kassim, A. Sharif, A. and Abdullah, A. H. (2007). Chemical modification of SAGO starch by solventless esterification with fatty acid chlorides. The Malaysian. Analy. Set, 11,395-399. 

Starch esters have been obtained by reactions of starch and carboxylic or sulfonic acid imidazolides in aqueous NaOH or nonaqueous solutions, as described in reference [226]. The esterification of dextran with butyric or palmitic acid using CDI in DMSO or formamide is discussed in reference [174]. 

Incomplete carbonization of sugar, starch or cellulose followed by sulfonation produces stable and very active catalysts [25]. These materials, denoted sugar catalysts , not only show higher activity than other solid acids in the esterification of waste oils, but also maintain more than 90% of their original activity even after 50 cycles and they are stable up to 275 °C [26]. 

Esterification Starch acetate - Esterification with acetic anhydride or vinyl acetate Acetylated distarch adipate - Esterification with acetic anhydride and adipic anhydride Starch sodium octenylsuccinate - Esterification by octenylsuccinic anhydride... 

The same observations apply to the graph of nitrating starch discussed in one of the following chapters, with the exception that the solubility of nitrostarch in nitrating mixtures is, however, a major factor. Thus mixed acids of poor sulphuric acid percentage dissolve nitrostarch, and esterification in such homogeneous systems proceeds more readily. 

Recently extensive investigations on the nitration of starch, mainly by using mixed nitric and sulphuric acid have been carried out by Kunz and T6th [46]. Their object was to determine the effect of the ratio of the components in the nitrating mixture and the activity of nitric acid in the mixtures on the nitrogen content of the nitrostarch, the heat of esterification, and the relation between the nitration temperature and the viscosity of the product. Their observations concerning the time of reaction are of special interest. This varies as a linear function of the nitration temperature. In the graph (Fig. 169) the relationship is shown for two mixed acids ... 

Although CDI was applied as early as 1972 as reagent for the esterification of starch and dextran, it has only scarcely been used up to now. Its renaissance during the last few years may be due to the fact that it became an affordable commercially available product. Among the first attempts for the esterification of polysaccharides via CDI is the binding of amino acids onto dextran. Besides CDI, -(thiocarbony diimidazole can be utilised to obtain the corresponding imidazolide [198]. The amino acids bound via this path are glycine, L-leucine, L-phenylalanine, L-histidine and L-alanyl-L-histidine. They are protected with N-trifluoroacetyl, N-benzyloxycarbonyl... 

Starch is an abundant, inexpensive polysaccharide that is readily available from staple crops such as com or maize and is thus is mostly important as food. Industrially, starch is also widely used in papermaking, the production of adhesives or as additives in plastics. For a number of these applications, it is desirable to chemically modify the starch to increase its hydrophobicity. Starch modification can thus prevent retrodegradation improve gel texture, clarity and sheen improve film formation and stabilize emulsions [108], This may, for example, be achieved by partial acetylation, alkyl siliconation or esterification however, these methods typically require environmentally unfriendly stoichiometric reagents and produce waste. Catalytic modification, such as the palladium-catalyzed telomerization (Scheme 18), of starch may provide a green atom-efficient way for creating chemically modified starches. The physicochemical properties of thus modified starches are discussed by Bouquillon et al. [22]. 

Hydrophobic starches are generated by a variety of reactions, for example by esterification with octenyl-substituted succinic acid anhydride.39 They can have the properties of a polymeric surfactant, which will generate a weak network with dispersed... 

Pretreatment of starch granules by esterification with ethylene-acrylic acid iono-mers has been reported to improve the properties of compression molded PE-starch materials compared to simple melt mixing of the three components.54 Improvements over no treatment with ionomer were limited to starch contents less than about 20%. 

Catalysis, enzyme-substrate and intermediate compound theory in homo-and heterogeneous, V, 51 Catalysts, for acetonation, III, 51 for acetylation of starch, I, 284, 286 Bourguel s, II, 109, 110, 113 for esterification of cellulose, I, 312 in oxidation of carbohydrates by halogens, III, 177... 

Monofunctional and/or Polyfunctional Esterification (Starch Esters) The starch esters are named individually, depending on the method of preparation. ... 

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