Starch etherification

Extended studies on starch etherification with C2 to C5 aliphatic alkylene oxides in alkaline slurries have been performed 944,945 This reaction was subsequently re-examined for hydroxypropylation.946 No significant effects were observed as a result of using added hydrogen peroxide, benzoyl peroxide, azodiisobutyronitrile, or K2S2O8.945 In all instances, including those studied without such additives, led to water- and alcohol-soluble thermoplastic materials. Further improvements involved etherification in either acetone or butanone in the presence of aqueous NaOH. Ethylene oxide was introduced incrementally.947 Etherification of starch... 

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. 

Etherification. Carbohydrates are involved in ether formation, both intramoleculady and intermoleculady (1,13). The cycHc ether, 1,4-sorbitan, an 1,4-anhydroalditol, has already been mentioned. 3,6-Anhydro-a-D-galactopyranosyl units are principal monomer units of the carrageenans. Methyl, ethyl, carboxymethyl, hydroxyethyl, and hydroxypropyl ethers of cellulose (qv) are all commercial materials. The principal starch ethers are the hydroxyethyl and hydroxypropylethers (see Cellulose ethers Starch). 

Etherification. A mixture of ethylene chlorohydrin ia 30% aqueous NaOH may be added to phenol at 100—110°C to give 2-phenoxyethanol [122-99-6] ia 98% yield (39). A cationic starch ether is made by reaction of a chlorohydfin-quaternary ammonium compound such as... 

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

Etherification Improved clarity of starch paste. Used in wide range of food... 

Starch (amylose and amylopectin) hydrolysis along with ester-fication, etherification or oxidation have been previously discussed as available methods for producing starch derivatives with improved water dispersibilities and reduced retrogradation potential (, ). Since oxidative and hydrolytic reactions are simple, easily controlled chemical modifications, starch-derived polymers made by hydrolysis alone or oxidative and hydrolytic processes were developed and tested. 

Etherification with Oxidation (Oxidized Starch Ethers)... 

Cellulose, the feedstock for cellulose ethers, is a polysaccharide like xanthane, guar and starch. It is a biopolymer made by photosynthesis and thus a renewable raw material. Cellulose is water insoluble, and only becomes water-soluble after hydrolysis and etherification [104, 105] (Fig. 5). 

Etherification of starch dialdehyde is possible. The reaction of starch dialdehyde with propylene oxide and other etherification reactions were described.530 Esterification of starch dialdehyde with carboxylic anhydrides stabilizes the viscosity and adhesiveness of starch dialdehyde.531 This adhesive is additionally blended with urea. 

Esterification of starch dialdehyde with chlorosulfonic acid in formamide gave a sulfate ester that could be transformed into an amide and methyl ester.532-536 The classical method of sulfonation, namely, by the action of sulfur trioxide in pyridine, is also applicable.537,538 Hemiacetals of starch dialdehyde result upon treatment with suitable alcohols in the presence of an acidic catalyst. In acetic media amides condensed with the carbonyl groups. Acetylation of starch dialdehyde with acetic anhydride is an obvious reaction. Esters with hexanedioic (adipic) acid were also prepared.537 Starch dialdehyde undergoes etherification with monochloroacetic acid in an alkaline medium.538... 

The reaction of starch with propylene oxide in alkali forms 0-(2-hydroxypropyl)starch.892,930-938 A granular derivative can be prepared by impregnating starch with acetic acid prior to its alkali treatment with and reaction propylene oxide.939 Etherification at 0-3 and 0-2 occurs at approximately the same rate, and the reaction at 0-6 is slightly less favorable.933 However, etherification at 0-2 has priority.940... 

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