Kinetics and mechanism of the decay of methyl cellulose‐manganate(VI) polysaccharide transient species–novel spectrophotometric kinetic trace of methyl cellulose hypomangate(V) gel intermediate polysaccharide

Abstract

Kinetics of the decay of methyl cellulosemanganate(VI) intermediate polysaccharide 22 ] have been followed spectrophotometrically in different strong basic solutions at different temperatures, as well as, in the presence of different concentrations of perchlorate salt. The reaction is base-catalyzed. Salt never affects the reactivity. The activation parameters have been evaluated and discussed in connection with the proposal mechanism.

A promising methyl ester of pectic acid polysaccharide in biomedicine and pharmaceutics applications: Oxidation of methyl ester of pectic acid by alkaline hexacyanoferrate(III). A kinetic and mechanistic orientation

“…The experimental results in the present redox reaction indicated that the oxidation kinetics was complex in nature. It has been reported that the alcoholic polysaccharides possess high affinity for deprotonation in alkaline solutions to give the more reactive alkoxides prior to the rate‐determining step as follows: where PS represents the alcoholic polysaccharides and PS − is the corresponding alkoxide formed. If such deprotonation occurs in the present work, the oxidation process should have been occurred between two negative charge anions as reactive species, hexacyanoferrate(III) and the formed alkoxide, respectively.…”

“…The experimental results in the present redox reaction indicated that the oxidation kinetics was complex in nature. It has been reported that the alcoholic polysaccharides possess high affinity for deprotonation in alkaline solutions 22,23,[42][43][44][45] to T A B L E 3 The activation parameters of the second-order rate constant (k n ) in the oxidation of pectin along with that for oxidation of other polysaccharides by alkaline hexacyanoferrate(III) give the more reactive alkoxides prior to the rate-determining step as follows:…”

“…In view of the forgoing arguments and our interest in the oxidation of polysaccharides by various oxidants in both alkaline and acidic media [27][28][29][30][31][32][33][34] in particular by the alkaline hexacyanoferrate(III) as an oxidant [19][20][21] in a series of investigations in our laboratory, we are prompted to undertake the present investigation of oxidation of methyl ester of pectic acid (pectin) by alkaline [Fe(CN) 6 ] 3− with the aim to verify and rectify the errors in derivation of rate-law expression of this redox reaction, which is reported elsewhere, 26 as well as to elucidate a suitable oxidation mechanism consistent with the kinetic results obtained. Again, this investigation aims to shed some light on the nature of electron-transfer mechanism and transition states in the rate-determining step in comparison to that reported for oxidation of the other polysaccharides by this oxidant in alkaline solutions earlier.…”

Oxidation of Some Sulfated Carbohydrates: Kinetics and Mechanism of Oxidation of Chondroitin-4-Sulfate by Alkaline Permanganate with Novel Synthesis of Coordination Biopolymer Precursor

“…Although, permanganate ion is a strong oxidizing agent which has been widely used for oxidation of most organic and inorganic compounds (Stewart, 1965;Lee, 1980;Fatiadi, 1987;Dash, Patel, & Mishra, 2009), a little attention has been focused to the oxidation of macromolecules by this oxidant. Eventhough, the kinetics of permanganate oxidation of some carbohydrates containing secondary alcoholic groups such as alginates (Hassan, 1993), pectates (Khairou & Hassan, 2000;Khairou, 2003;Abdel-Mohsen & Nassr, 2010), carboxymethyl cellulose (Shaker, 2001) and methyl cellulose (El-Khatib, 2002;Shaker, El-Khatib, & Mahran, 2007) in alkaline solution has been studied by us for the first time. Unfortunately, the oxidation of sulfated carbohydrates has received a little attention .…”

“…In view of the above aspects in addition to our interest in the oxidation kinetics of carbohydrates by either this oxidant (Hassan, 1993;Khairou & Hassan, 2000;Khairou, 2003;Abdel-Mohsen & Nassr, 2010;Shaker, 2001;Shaker, El-Khatib, & Mahran, 2007;El-Khatib, 2002; or by other oxidants Zaafarany et al, 2009;, the present work seems to be of great importance with the aims at shedding more highlights on the nature of the formed intermediates in terms of electron-transfer processes and the transition states in the rate-determining step as well as to compare the results obtained with that previously reported for oxidation of other sulfated carbohydrates by this oxidant in alkaline solutions in an attempt to elucidate a suitable reaction mechanism for oxidation in these redox systems. In addition, this work aims to synthesize a novel coordination biopolymer chelating agent.…”