Wet oxidation of organic matter employing perchloric acid at graded oxidation potentials and controlled temperatures

A new modified apparatus has been described for use in the wet ashing of organic matter using boiling, controlled concentrations of perchlouc acid as oxidant Typical operative procedures and manipulations are discussed and a number of direct applications. to various types of materials has been demonstrated Cellulose, proteins, and sugars and materials predominating in these types, have been selected as best applicable examples Perchloric acid concntrations tested were from 55-–68 percent and intermediate concentrations The procedures described provide conditions which though effective are less encumbered by the implication of ha/ard often charged against 70–72 5 per cent perchloirc and in similar previously published and widely applied procedures.     

Electrocatalytic oxidation of cyclohexane by molecular oxygen in non-aqueous solvents in the presence of perchloric acid and perchlorates

Several new electrocatalytic systems are described for the oxidation of cyclohexane by molecular oxygen at room temperature. The solvent is acetonitrile. Perchloric acid and perchlorates are used as supporting electrolytes. The maximum electrochemical yield amounts to 9.6% and is observed in the presence of perchloric acid.

---

, . , — . 9,6% — .

     

Kinetics and mechanism of the oxidation of acetaldehyde by chromic acid in perchloric acid

Summary The oxidation of MeCHO by chromium(VI) has been studied in HClO₄ medium over a wide range of experimental conditions and has been found to obey the rate law;v=k[MeCHO][HCrO ₄ ^– ][H⁺]. The calculated H and-S values for the reaction are 30±2kJ mol^–1 and 171±7J mol^–1deg^–1, respectively. The mechanism is discussed in terms of carbon-hydrogen bond cleavage.     

Hexacyanoferrate(III) oxidation of n-valeric and iso-valeric acid hydrazides in perchloric acid

Summary The kinetics of the title reaction were determined spectrophotometrically. The oxidation was second order; but first order with respect to both [hexacyanoferrate(III)]₀ and [hydrazide]₀. The effect of [HClO₄] on the reaction rate was curious; as the HClO₄ concentration increased the rate decreased and, reaching a minimum. The rate was slightly enhanced by an increase in ionic strength, but was insensitive to added salts, such as NaClO₄, NaNO₃, NaCl, KCl, Licl and K₄Fe(CN)₆ at constant ionic strength. Addition of MeOH retarded the oxidation rate and the entropy of activation was negative. Carboxylic acids and N₂ were identified as the oxidation products. A radical mechanism and a rate law consistent with the experimental results is proposed.     

Kinetics and mechanism of oxidation of glycine by iron(iii)-1,10-phenanthroline complex in perchloric acid medium

Kinetics and mechanism of oxidation of glycine by iron (III)-1,10-phenanthroline complex has been studied in perchloric acid medium. The reaction is first order with respect to iron(III) and glycine. An increase in (phenanthroline) increases the rate, while increase in [H⁺] decreases the rate. Hence it can be inferred that the reactive species of the substrate is the zwitterionic form and that of the oxidant is [Fe(phen)₂(H₂O)₂]³⁺. The proposed mechanism leads to the rate law as elucidated.     

Evidence of protonation during the oxidation of some aryl alcohols by permanganate in perchloric acid medium and mechanism of the oxidation processes

The oxidation of benzyl alcohol and methoxy-, chloro-, and nitro- substituted benzyl alcohols by permanganate has been studied in aqueous and acetic acid medium in presence of perchloric acid. The reaction is first-order in [MnO₄^?] and [XC₆H₄CH₂OH], but the order is complex with respect to [H⁺]. Different thermodynamic parameters have been evaluated. The reaction occurs through the protonation of alcohol in a fast preequilibrium followed by a slow rate-determining oxidation step. A two-electron transfer oxidation step has been suggested for benzyl alcohol and chloro- and nitro- substituted alcohols, while the oxidation of methoxy compounds involves a one-electron transfer via a free-radical mechanism. © 1995 John Wiley & Sons, Inc.     

The determination of copper in whetlerized carbon following destructive oxidation of carbon employing hot concentrated perchloric acid

The determination of copper in whetlerized gas mask carbon has been described. The sample is “ashed” by wet oxidation employing mixed HN0₃ + HCIO₄ + H₂SO₄. The reaction is catalyzed through the addition of small amounts of chromium.The copper recovered as copper sulfate following wet ashing is reduced to Cu(I) by potassium iodide in. acetic acid solution (with previous neutralization of sulfuric acid by sodium hydroxide). The liberated iodine is then titrated employing standard sodium thiosulfate solution with starch as indicator.Individual analyses require 25–30 minutes for complete analysis.     

Kinetics of the oxidation of some polycyclic aromatic hydrocarbons by lead tetraacetate in aqueous acetic acid and perchloric acid medium

The state of metal cations in CuCr₂O₄/-Al₂O₃ catalysts under its operation in catalytic heat generators has been examined. IR spectra of adsorbed CO indicate copper ion reduction in the catalyst to Cu⁺, whose surface concentration was determined. Diffuse reflectance spectra have revealed that the initial catalyst contains Cr(VI), disappearing after reaction.

---

CuCr₂O₄/-Al₂O₃ (). - CO , Cu⁺. Cu⁺. , Cr(VI), .

     

Titrimetric, coulometric and spectrophotometric determination of manganese following perchloric acid oxidation in the presence of pyrophosphate

Manganese is oxidized quantitatively to a violet, tervalent pyrophosphate in a boiling mixture of equal parts of perchloric acid and phosphoric add. This Mn(III) can be titrated potentiometrically or coulometrically with iron(II); it can also be measured spectrophotometrically. If the titrimetric method is carried out with titanium (III) or chromium(II), iron can also be titrated immediately after the manganese. The methods were applied to a new reference sample, ISU 600 Manganiferous Iron Ore, and to manganese ore, spiegeleisen, ferromanganese, and rail steel. Manganese(II) oxalate dihydrate has been reinvestigated as a primary standard and is highly recommended.     

Ionization potentials and donor properties of nucleic acid bases and related compounds

The first vertical ionization potentials of guanine, adenine, hypoxanthine, xanthine, cytosine, thymine, uracil and purine have been determined by HeI photoelectron spectroscopy. The potentials increase in the above order and are assigned to ionization from the highest π level. The experimental results are compared with valence shell SCF calculations, and the correlation between the association constants of these molecules with riboflavin and their donor properties is discussed. Detailed spectra will be presented and discussed in a forthcoming paper.     

Oscillatory behavior during the oxygen oxidation of ascorbic acid

The oscillatory phenomenon was observed in aqueous solution during the oxidation of ascorbic acid by oxygen. Even though the exact number and amplitude of the oscillations could not be exactly duplicated for each and every run, such factors as temperature, concentration of ascorbic acid, cupric ions, and pH affecting the oscillatory behavior were studied, and those regions where oscillations occurred were delineated. A mechanism consistent with the oscillatory behavior is proposed and discussed.     

Kinetics and mechanism of oxidation of D-altrose by aqua-cerium(IV) in perchloric acid medium

Kinetics of the oxidation of D-altrose by Ce(IV) perchlorate has been studied in perchloric acid medium. At equivalent concentrations the overall order of the reaction is two, being unity in each reactant. The reaction is characterized by a primary positive kinetic salt effect. Perchloric acid has been found to enhance the rate, while the addition of the reaction products retards the rate. No evidence for initial complexation has been obtained. Thermodynamic parameters have been determined and a mechanism consistent with the observed results is proposed.

---

D- Ce(IV) . , . . , . . , .

     

Kinetics and mechanism of oxidation of hypophosphite by Waugh-type enneamolybdomanganate(IV) in perchloric acid

The reaction between hypophosphite and enneamolybdomanganate(IV) in perchloric acid was carried out under pseudo-first-order conditions keeping large excess of hypophosphite. The order in oxidant was found to be unity and that of hypophosphite was found to be less than unity. The reaction proceeds with prior formation of complex between the reactants followed by its rate determining decomposition. The accelerating effect of hydrogen ions on the reaction is due to the formation of active hexaprotonated oxidant species. The formation of the complex is supported by kinetic results and also by spectrophotometric study. The product of the reaction was found to be phosphitomolybdate, [H₁₀(HP)Mo₆O₂₆]²⁻, which was confirmed by FTIR study and AAS analysis. The reaction involves direct two-electron transfer step without any free radical intervention. The effect of ionic strength, solvent polarity and the activation parameters were also in support of the mechanism proposed.     

Removal of graphite by oxidation with perchloric acid plus periodic acid Inapplicability to the spectrophotometric determination of manganese in steel

An attempt has been made to improve the Willard and Greathouse periodate method for the determination of manganese in high-carbon steel and cast iron by oxidizing the graphite with periodic acid in the presence of perchloric acid and phosphoric acid. Graphite is rapidly oxidized at 150 degrees by this mixture but manganese is lost by volatilization as the heptoxide and decomposition of the latter on hot surfaces to manganese dioxide. No way was found for either the quantitative removal and recovery of manganese by volatilization or for quantitative return to the main solution. The spectrophotometric determination of manganese in the supernatant liquid after allowing graphite to settle yields imprecise but not wholly unacceptable results; for the highest accuracy, graphite should be removed along with silica following dehydration of the latter with perchloric acid.     

Kinetics and mechanism of the oxidation of 2-furancarbox-aldehyde by thallium(III) in perchloric acid solutions

The kinetics of the oxidation of 2-furancarboxaldehyde by thallic perchlorate at 50°C obeys the rate law

Kinetics of oxidation of methanol and mono-deutero-methanol by chromium(VI) in perchloric acid medium

Kinetics of the oxidation of methanol and mono-deutero-methanol by Cr(VI) over a wide range of temperature (25–40°) have been studied in perchloric acid medium at constant ionic strength (μ = 1.0 M) adjusted with sodium perchlorate. Each reaction is first order with respect to the substrate and dichromate concentrations but the order with respect to [H⁺] is nearly 3 in each case. Both these reactions take place at almost the same rate under identical experimental conditions. The activation parameters of the reactions are not widely different and the values of ΔH3 and ΔS3 for the oxidation of methanol are 79.5 kJ mole ^-1 and - 38.1 J deg^-1 mole^-1 respectively, whereas the corresponding values for the deuterated compound are 83.8 kJ mole^-1 and -23.9 J deg^-1 mole^-1. The probable mechanism of the reactions is discussed.     

Kinetics and mechanism of the ruthenium(III)-catalysed oxidation of aminoalcohols by chloramine-T in perchloric acid

Summary The kinetics of the ruthenium(III) catalysed oxidation of 2-aminoethanol, 3-aminopropanol, diethanolamine and triethanolamine by chloramine-T in HClO₄ medium have been studied. The reactions exhibits first order rate dependence with respect to the oxidant and to the catalyst, and are zeroth order with respect to the substrate. The rate of oxidation is proportional to k[HClO₄]/{k+k'[HClO₄]} where k, k and k' are constants (a mixture of elementary rate constants and equilibrium constants). A suitable mechanism consistent with the observed kinetic data is proposed.     

The oxidation of organic compounds by tervalent manganese compounds-II The determination of mandelic acid with a tervalent manganese standard solution in perchloric acid medium

An indirect titrimetric determination of mandelic acid, based on its oxidation by a standard solution of hexa-aquomanganese(III) in perchloric acid medium, is described.