Mild oxidation of starches with aqueous bromine

The effect of bromide in the hypochlorite oxidation of amylodextrins (short chain amylose) and inulin on the reaction rate was investigated. It was found both in the linear dextrins and inulin oxidation that the rate increases linearly with the sodium bromide concentration, which proves the catalytic effect of this substance. The origin of the catalysis is the rapid Br−/OCl− conversion. The second‐order rate constant of the reaction Carbohydrate + HOBr/OBr− → polycarboxylates + HBr/Br− was determined at pH 9.0 and 294‐298 K. The activation energy for the oxidation of amylodextrins amounts to 67 kJ.mole−1. The highest rate was found at pH 8.25. The reaction rate is almost independent of pH in the region 8.5–9.5. Because of the simultaneous occurrence of bromine, Br3−. hypobromous acid and hypobromite in the pH region investigated, it is difficult to elucidate the oxidation mechanism.

Section: Mechanismmentioning

confidence: 99%

“…In literature no rate constants at these pH values are found. For a comparable system, but at pH 8 and 303K Ziderman and BelAchye [14] report for the HOBr/OBr-oxidation of starch the pseudo-first-order rate constant (excess starch)…”

Section: Experiments With Inulinmentioning

confidence: 99%

The Catalytic Effect of Bromide in the Hypochlorite Oxidation of Linear Dextrins and Inulin

Besemer

Bekkum

1994

“…Potze and Hiemstra used a 0.125-0.0125 NaBr/ NaOCI molar ratio. However, it is evident from the literature that the rate of the oxidation of starch with hypobromite/ hypobromous acid is substantially higher than that of the reaction with sodium hypochlorite/hypochlorous acid [46,471 and the disappointing results of Floor may be attributed to the low catalyst concentration. Apparently, there is a need for further research regarding this subject.…”

Section: Picmentioning

confidence: 99%

Dicarboxy‐Starch by Sodium Hypochlorite/Bromide Oxidation and Its Calcium Binding Properties

Besemer

Bekkum

1994

Various aspects of the glycolic oxidation of the glucose units of starch with stoichiometric amounts of sodium hypochlorite applying sodium bromide as the catalyst have been investigated. The main objective of the study was to optimize the reaction conditions for the preparation of dicarboxy‐starch and to establish the calcium sequestering capacity of the material. The products, polycarboxylates, are obtained in high yields (90‐95%) and they have a sequestering capacity up to 1.4 mmole Ca/g, which is somewhat higher than that of the materials obtained in a non‐catalyzed oxidation. This result is attributed to the facts that the reaction with sodium bromide may be carried out at higher pH (>9) than the non‐catalyzed reaction and that a relatively low concentration of hypochlorite throughout the process could be maintained. In this way the decomposition of hypochlorous acid/hypochlorite, especially occurring at high concentration of hypochlorous acid at lower pH (6‐8) is prevented. Other advantages of this procedure are the colourless appearance of the materials and the higher reaction rate. The feasibility for largescale preparation follows from the results of a few exploratory experiments, including an electrochemical preparation.

“…As early as 1972, Ziderman et al reported the oxidation kinetics of starch by diluted bromine water, however, the reaction conditions were not studied in detail. Recently reports believed that sodium bromide can be used as a co‐catalyst in the oxidation system such as NaClO/TEMPO/NaBr system and NaClO/NH 2 OH · HCl/NaBr system, where sodium bromide was oxidized by sodium hypochlorite to form sodium hypobromite, which was subsequently used as an oxidizer to react with starch to produce oxidized starch.…”

Section: Introductionmentioning

confidence: 99%

Rapid Preparation of Oxidized Starch with High Carbonyl Contents Using NaBrO as Oxidizer

Yang¹,

Wang²,

Zhang³

et al. 2019

In this work, oxidized starch with high carbonyl contents is obtained in a rather simple way using corn starch as raw material and NaBrO as an oxidizer. The produced oxidized starch is evaluated by measuring the carboxyl content, carbonyl content, yield, and the intrinsic viscosity. The influences of pH, reaction time, temperature and oxidizer content on carbonyl content, carboxyl content, intrinsic viscosity, and yield of the oxidized starch are investigated in detail. It is found that the reaction conditions are readily controlled, and the higher carbonyl contents as well as yield of oxidized starch can be obtained compared with those reported previously, leading to promising products. The formation of carboxyl and carbonyl groups on the oxidized starch is confirmed by FT‐IR. The changes of crystallinity and the apparent morphology of oxidized starch are characterized with XRD and SEM, respectively.