Halogenated starches

Halogenated starch may incorporate halogen atoms bound either covalently ionically, or by other interactions, such as van der Waals and dispersion forces. Bonding of the latter type is responsible for the formation of various starch-halogen and halogenated compound-starch complexes. Since they were recently reviewed4 such compounds are omitted from this section. 

Additional information on halogenated starches has been reported by Whistler.2279 2280... 

Fluorine in the atmosphere can be detected by chemical methods involving the displacement of halogens from haUdes. Dilute fluorine leaks are easily detected by passing a damp piece of starch iodide paper around the suspected area. The paper should be held with metal tongs or forceps to avoid contact with the gas stream and immediately darkens when fluorine is present. 

Cationic Starches. The two general categories of commercial cationic starches are tertiary and quaternary aminoalkyl ethers. Tertiary aminoalkyl ethers are prepared by treating an alkaline starch dispersion with a tertiary amine containing a P-halogenated alkyl, 3-chloto-2-hydtoxyptopyl radical, or a 2,3-epoxypropyl group. Under these reaction conditions, starch ethers are formed that contain tertiary amine free bases. Treatment with acid easily produces the cationic form. Amines used in this reaction include 2-dimethylaminoethyl chloride, 2-diethylaminoethyl chloride, and A/-(2,3-epoxypropyl) diethylamine. Commercial preparation of low DS derivatives employ reaction times of 6—12 h at 40—45°C for complete reaction. The final product is filtered, washed, and dried. 

Starch-Iodide Paper.—Used as an indicator for nitrous acid, and for halogens and other oxidising agents. Turned bluish-violet by a trace of oxidising agent and brown by excess. 

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... 

Free Halogens Mix 10 mL of sample with 10 mL of 10% potassium iodide solution and 1 mL of starch TS. Shake the mixture vigorously for 2 min. A blue color does not appear in the water layer. 

Free Halogens Transfer 10 mL of sample to a separator, add 25 mL of water, and shake vigorously for 1 min. Allow the layers to separate, and then remove and discard the lower sample layer. Add 1 mL of potassium iodide TS and a few drops of starch TS to the aqueous phase, and allow it to stand for 5 min. A blue color does not appear. 

The widespread use of bleaching agents containing chlorine, and of the halogens themselves as modifying agents for starch and cellulose should be based on a more fundamental study of the reactions involved. 

Cleaning Up Place dichloromethane solutions in the halogenated organic solvents container and organic solvents in the organic solvents container. The alumina should be placed in the alumina hazardous waste container. If it should be necessary to destroy 3-chloroperoxybenzoic acid, add it to an excess of an ice-cold solution of saturated sodium bisulfite in the hood. A peracid will give a positive starch/iodide test (blue-purple color). 

Acid catalysts other than sulfuric acid have been tested with acetic anhydride for use in starch acetylation. None of these, however, seem to exert as powerful a catalytic action as sulfuric acid, and some, particularly the halogen acids, cause even more extensive depolymerization of the starch. For example, acetic anhydride saturated with hydrogen chloride rapidly dissolves starch and converts it to low molec-... 

In general, starch triacetates are soluble in acetic acid and, except perhaps for potato starch triacetate, are soluble in chloroform, 1,1,2-tri-chloroethane, tetrachloroethane, and other halogenated hydrocarbons. High grade starch triacetates do not appear to be soluble in ethyl acetate or alcohol, while some controversy exists as to the extent of their solubility in pyridine and acetone. Waxy com starch triacetate, perhaps due to its smaller molecular weight, is readily soluble in a wide variety of organic solvents. 

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. 

The solubility of starch acetates depends on the d.s. and the d.p. Starch acetates of 10-15% are soluble in water at 50-100 °C and are insoluble in organic solvents. Starch acetates of 40% or more are soluble in aromatic hydrocarbons and halogenated aliphatic hydrocarbons. 

Chlorine is more potent an oxidant than is bromine but less so than fluorine (Clifford, 1961a). Thus, chlorine is able to oxidize both bromide and iodide ions to Br2 and I2, respectively, whereas fluorine oxidizes chloride, bromide, and iodide to their corresponding halogens. The oxidizing ability of chlorine is the basis for the starch-iodide test for chlorine. Here, a mixture of potassium iodide, soluble starch, and zinc chloride produces a blue-violet color in the presence of chlorine. Unfortunately, and like many spot tests, this is a nonspecific test and gives a positive result with many oxidants, for example, bromine. 

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