Oxidation of Wheat Starch With Alkaline Hypochlorite

Abstract

A B S T R A C T T h e starch was oxidized withThe oxidation of various species of starch with alkaline hypochlorite, a process of industrial as well as academic interest, has been studied for many years. Reviews (1, 2) of the subject show that most of the early interest was attracted to the changes produced by various amounts of oxidant in such properties as viscosity and copper-reducing power, ease of retrogradation, and the adsorption of dyes. Degradation products were isolated and identified in only a very few instances. McKillican and Purves (3) more recently obtained evidence that hypochlorous acid near pH 4 oxidized wheat starch in the second and sixth positions of the glucose residues to yield in part 2-lteto and uronic acid derivatives. Whistler and his collaborators (4, 5), employing corn amylose and ainylopectin with hypochlorite kept a t 25" and a t various pIH values between 3 and 13, dialyzed the products and showed that both the dialyzable and the non-dialyzable portions yielded D-glucose, glyoxylic acid, D-erythronic acid, and D-erythronolactone after hydrolysis with acid. Oxidations near pH 7 produced the maximum amount (about 0.3 mole) of glyoxylic acid. The present research provided additional information about the course of the reaction a t pH 12 and 20".Preliminary experiments, employing 0.12 M and 0.06 M calcium hypochlorite with illole ratios per CsH1005 unit of 1: 1 or 1 :0.5, confirmed the observation (5) that such oxidations were exceedingly slow. Sodium hypochlorite yielded solutions from which it was more difficult to isolate the organic products. The use of a greater excess (mole ratio, 5.5:l) of a more coilcentrated (0.43 M ) hypochlorite increased the speed of the oxidatioil to a convenient value, and had the additional advantage that the rate coilstant for the disappearance of hypochlorite would tend to follow the first-order ltinetic equation. A semilogarithmic plot of the data (Fig. l , plot A) became linear after about 76 hours and could be represented by the equation log 0.24/(0.24 -b) = 2.2 X 10-3T, where b was the concentration of hypochlorite consumed a t time T, the units being moles, liters, and hours. Substitution of values of T between zero and 76 hours then yielded values of b froin which, by difference froin the observed values, the corresponding data bl for the initial, fast reaction could be calculated. These data (plot B) also fitted a first-order equation, log 0.19/(0.19 -bl) = 2 . 2 f 0.1 X lo-? T.The above calculatioils suggested that the oxidatioil of starch with hypochlorite a t pH 12 consisted of a relatively rapid reaction consuming 2.34 moles of l~ypocl~lorite

Coalescence Versus Condensation of the Lignin in Wood in Sulphite Pulping

“…For instance, such reactions may be indicated by an increase in the amount of biphenyl groups (28,29) or in the yields of benzene polycarboxylic acids (30,31,32,33,34) obtained from the lignin materials by alkaline permanganate oxidation, although in this case the accessibility of the lignin structure will also be a factor. For instance, such reactions may be indicated by an increase in the amount of biphenyl groups (28,29) or in the yields of benzene polycarboxylic acids (30,31,32,33,34) obtained from the lignin materials by alkaline permanganate oxidation, although in this case the accessibility of the lignin structure will also be a factor.…”