Starch carboxylic acids

Poly(starch-g-((l-amidoethylene)-co-(sodium 1-carboxylatoethylene))). Poly(l-amidoethylene) is, however, rarely used as a viscosifier. Instead, the homopolyraer is reacted with base (hydrolyzed with NaOH) to convert some of the amide units of the polymer to carboxylic acid units. The acid units on the hydrolyzed polymer dissociate in water and produce a polyanionic polymer. This polyelectrolyte expands in water because of ion-ion repulsion and, as an enlarged molecule, is a better viscosifier. 

The cleavage of 1,2-diols can be inexpensively achieved at a nickel hydroxide electrode [126], while chemically more expensive reagents such as PbjOAc) or 104 must be used. The latter can be used as mediator for the indirect anodic cleavage of starch [146]. Double bonds can be cleaved at the anode to carboxylic acids by applying the double mediator RuCh, 104 [147]. 

These carbonaceous catalysts can be obtained by the sulfonation of incompletely carbonized organic compounds [42]. Note that starch and cellulose can be used as carbon precursor [43, 44]. After the incomplete pyrolysis of the carbon precursor, the SO3H groups have been introduced by sulfonation with sulfuric acid (Scheme 3). After this treatment, the presence of phenolic hydroxyl, carboxylic acid, and sulfonic groups at the surface of these amorphous carbonaceous materials has been demonstrated. 

Titratable Acidity. The possibility of carboxylic acid group generation from excessive oxidation of corn starch was monitored by titratable acidity (TA). A 0.01 N NaOH solution was used to titrate a dilute aqueous starch suspension (20 mL of a 5% w/v sample) for the presence of acidic functional groups, using phenolphthalein as the indicator dye. An unreacted starch sample was also titrated to yield a sample blank value. TA values were expressed as mL of base required to reach the colorimetric phenolphthalein and end-point. 

In practice several problems have had to be overcome before this apparently attractive method of sizing could be implemented efficiently. Since the ketene or the anhydride have to react with hydroxyl groups, they will also react readily with water i.e. the molecules are hydrolysed to give non-reacting carboxylic acids (Figure 2). Some means must therefore be found to permit addition of the sizes to the wet-end of a paper machine, and then to ensure that they are retained within the wet paper web in such a way that an adequate size film is deposited on fibres in the dried sheet. This is made more awkward by the essentially hydrophobic nature of the molecules. The means adopted is to prepare emulsions of the sizes, often using cationic starch as a stabiliser and retention aid. 

Maize starch may be separated after irradiation into several fractions, based on solubility in alcohol and aqueous alcohol. The size of the fractions and their composition depends on the radiation dose, as shown in Table X which also shows the distribution of organic products of destruction (aldehydes and carboxylic acids) in particular fractions.118 The relations presented in this Table are S-shaped. Under irradiation with increasing doses, the destruction of starch obviously increases. The nature of the increase of acidity in com starch has also been studied by Athanassiades and Berger.119 Thollier and Guilbot120 have conducted similar studies on potato starch, and Raffi et al99 have extended their studies to more varieties of starch. The results expressed as free and total acidities, as well as the quantity of formic acid at equilibrium water content, are given in Table XI. These data vary rather nonlinearly with increase of the irradiation dose and water content. 

The glow electrolysis technique (electrolysis with an anode immersed in the solution and the cathode above the surface) at 600-800 V dc and 300-500 mA converts a solution of starch into ethylene, methane, hydrogen, and both carbon mono- and dioxides.323 Electrochemical methods for converting polysaccharides and other biomass-derived materials have been reviewed briefly by Baizer.324 These methods are mainly oxidations along a potential gradient, which decreases the activation energy of the reactants. Starch in 5 M NaOH solution is oxidized on platinum electrodes to carboxylic acids with an activation energy of about 10 kcal/mol. In acidic media oxidation takes place at C-l followed by decarboxylation and oxidation at the C-2 and C-6 atoms.325... 

Alcohols, biochemical production from carboxylic acids, IV, 108, 109 effect on aqueous leaching of starch, I, 263... 

In this experiment you will work with a natural polymer called alginic acid that comes from seaweed. Alginic acid is a polysaccharide as are cellulose and starch. Unlike cellulose and starch, however alginic acid as the name implies contains acidic functional groups called carboxylic acids. Salts of alginic acid are used as food additives, especially as a thickener. 

Starch complexes with aromas and flavoring agents are usually synthetic in origin. In nature, starch sometimes includes some aroma- and flavor-genic components that generate flavor and aroma on processing (see, for instance, ref. 678). Such agents include mainly aldehydes, ketones, and carboxylic esters however, hydrocarbons, alcohols, carboxylic acids, and haloalkanes have also been used. 

Sorption of carboxylic acids on starch is useful in their thin-layer chroma-tograhic separation.727 Amino acids are particularly well separated on thin layers of starch (see reviews728 733). Rice starch is suitable for this purpose, whereas maize starch is not. Starch has been used for resolution of racemates.734,735... 

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