Starch carbamates reactions

Starch carbamate block copolymers are biodegradable.2643 During production, the reaction mixture can be supplemented with vegetable derivatives, molasses,... 

Chemical modifications may also include the derivatization of starch by reaction of its hydroxyl groups with alkylene oxides. Other suitable substances are such that form ether linkages, ester linkages, urethane linkages, carbamate linkages, or isocyanate linkages. The degree of substitution of the chemically modified starch varies from 0.05 to 0.2. 

For these and a variety of special non-food purposes esters with higher fatty acids, succinic, adipic and citric acids and carbamates (reaction products with urea), have also been prepared. Examples of starch ethers are 2-hydroxyethyl and 2-hydroxypropyl starches prepared by reaction of starch with oxirane (ethylene oxide) and methyloxirane (propylene-l,2-oxide). The reaction occurs preferentially at the secondary hydroxyl groups at C-2, with less on the C-3 and C-6 hydroxyl groups. The most common products are those shown in Figure 4.15. The degree of substitution tends to be <0.2. According to the reaction conditions, polyoxaalkyl starches ... 

Starch reacts with isocyanates to produce carbamates (urethanes), which are esters of carbamic acid. Several reactions of starch with phenyl-, various aryl-, 1-naphthyl-isocyanates or 1,6-hexamethylene- and 2,4-tolyl-diisocyanates were conducted either in pyridine or morpholine below the boiling point of these solvents.2546-2548 In each case all three hydroxyl groups of the glucose units reacted to give tricarbanilates, provided a sufficient amount of the isocyanate reagent was used. 

Cationization of carbamates is possible by reacting starch with amides in the presence of mineral or carboxylic acids2618 or by utilizing the Mannich reaction.2619... 

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