Starch Esters of Higher Fatty Acids

Higher aliphatic esters of starch are generally prepared by treating starch with the acid chloride in the presence of alkali or a tertiary organic base such as pyridine, quinoline, picoline, or dimethylani- 

Starch dilaurate is prepared by treating 1 part-of dry starch in 2.5 parts of pyridine and 3 parts of toluene with 5 parts of lauroyl chloride for two hours at 100 . The product is soluble in benzene, chloroform, and halogen derivatives of acetylene, but is insoluble in water, alcohol, and acetone. On evaporation of a benzene-chloroform solution it forms a brittle film. 

Starch palmitate is prepared by treating 1 part of starch in a mixture of 4 parts of benzene and 1.8 parts of pyridine with 6 parts of palmitoyl chloride and 4 parts of benzene for thirty minutes at 60° and precipitating the product with ethanol. Quinoline may be substituted for the benzene and pyridine. Because of the high boiling point of quinoline, an elevated esterification temperature can be used and triesters produced in about three hours. 

Starch laurate benzoate is prepared by mixing equal parts of starch and of a 40% sodium hydroxide solution, heating in benzene to the reflux temperature and then adding slowly a mixture of benzoyl chloride and lauroyl chloride. After a few minutes, the mixed ester is formed. 

Starch dilaurate is prepared by treating 1 part of dry starch in 

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Junistia L, Sugih AK, Manurung R, Picchioni F, Janssen LPBM, Heeres HJ. Synthesis of higher fatty acid starch esters using vinyl laurate and stearate as reactants. Starch/Starke 2008 60 667-75. 

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 ... 

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). 

Volatile fatty acid homologs higher than acetic acid have not been found as natural products of woody plants, although such acids and their esters are important components that contribute to the organoleptic properties of fruits. Nevertheless, propionic, butyric, valeric, and caproic acids occur in wetwood, in addition to elevated levels of acetic acid, as anaerobic fermentation products of starch (34, 36, 37, 43). For example, the concentration of acetic, propionic, and butyric acids of 0 to 3 mM in normal sapwood of white fir increases to as much as 38, 55, and 23 mM, respectively, in the wetwood of some fir species (38). The volatile fatty acids in gum turpentine and in the low wine (the aqueous phase of turpentine distillation) and turpentine tailings (24) also are likely the product of anaerobic fermentation. However, it should be noted that the oleoresin turpentine from Pinus sabiniana consists primarily of -heptane (22), and the turpentine from R jeffreyi contains a significant proportion of -heptane (22) and smaller amounts of A2-pentane, nonane, and undecane (39). The -heptane is derived not through the mevalonate pathway but rather by decarboxylation of octanoic acid (32). Presumably, the other hydrocarbons are also formed by decarboxylation. 

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