Agents, Oxidizing

Oxidizing agents Colour producing agents Chlor producing agents Other chemicals 

Binding agents Paper or paper-made parts 

Parts made of cotton, wool, hemp, silk etc. 

Cotton seeds etc. Parts made of wood Parts made of metal Parts made of bamboo 

Molecular weight 101.11 colourless crystals of the rhombic system specific gravity 2.109(16°C) makes transition to trigonal system at 129°C  

Oxidizing agents fall into two main categories  

Epoxidation is the addition of a single oxygen atom to an alkene to form an epoxide. 

The weak n bond of the alkene is broken and two new C - O a bonds are formed. Epoxidation is typically carried out with a peroxyacid, resulting in cleavage of the weak 0-0 bond of the reagent. 

Epoxidation occurs via the concerted addition of one oxygen atom of the peroxyacid to the it bond as shown in Mechanism 12.4. Epoxidation resembles the formation of the bridged halo-nium ion in Section 10.13, in that two bonds in a three-membered ring are formed in one step. 

One step All bonds are broken or formed In a single step. 

Some common oxidizing agents are classified according to stability in Table 6.6. 

Substances in column 1 must be stored/handled so that they cannot contact corresponding substances in column 2 under uncontrolled conditions, or violent reactions may occur. 

Acetic acid Chromic acid, nitric acid, hydroxyl-containing compounds, ethylene glycol, perchloric acid, peroxides, or permanganates 

Acetone Concentrated nitric and sulphuric acid mixtures 

Acetylene Chlorine, bromine, copper, silver, flourine or mercury 

Aluminium nitrate Ammonium persulphate Barium nitrate/peroxide Calcium nitrate/peroxide Cupric nitrate 

Hydrogen peroxide solutions (8-27.5% by weight) Lead nitrate 

Lithium peroxide/hypochlorite Magnesium nitrate/perchlorate Nickel nitrate 

Potassium dichromate/nitrate/persulphate Silver nitrate 

Alkali and alkaline earth metals, e.g. sodium, potassium, lithium, magnesium, calcium, powdered aluminium Anhydrous ammonia 

Hydrocarbons (benzene, butane, propane, gasoline, turpentine, etc) 

Hydrocyanic acid Hydrofluoric acid, anhydrous (hydrogen fluoride) 

Other important oxidizing agents used are azodicarbonamide and cupric sulfate (Stauffer 1990). Azodicarbonamide is used instead of potassium bromate and supplemented in baking flours by millers (Chapter 7). 

Chromium(vi).—Quantitative data for Cr and the other oxidizing agents will be found in Table 2. The use of chromium(vi) as mi oxidant has recently been reviewed in its reactions with transition-metal complexes. Kinetic studies of the equilibrium 

The oxidation of cobalt(n) complexes with nitrilopolyacetic acid ligands, Y (edta, diethylenetriaminepenta-acetic acid, /ra/i5-l,2-cyclohexanediamine-tetra-acetic acid). 

Chromium(iv) has also been postulated as an intermediate in oxidations using chromium(vi). Several types of reactions involving this species have been described including disproportionation and oxidation-reduction, e.g. 

Evidence for such processes has been derived from studies on the stoicheio-metries of Cr oxidations of ligands which will be dealt with more fully in the next chapter. 

Ohashi, A. Ohnuma, K. Yamamoto, and Y. Kurimura, Nippon Kagaku Zasshi, 1971, 51 (Chem. Abs., 1971, 74, 130 972g). 

Cerium(IV).— The oxidation of vanadium(iv) by cerium(rv) has been studied in 1— 2M perchloric acid, the reaction being first-order with respect to each reactant. Under the experimental conditions prevailing, the predominant oxidizing species is CeOH +, the reaction being 

The dependence of the rate on [H+], which in a previous study suggested an increase with increasing hydrogen-ion concentration, has been shown to be anomalous, the variation being expressed in the form 

The cerium(iv) oxidation of ferrocene-l,T-disulphonic acid in sulphate media has been described, kinetic data being derived from potential-time curves. Three moles of oxidant are consumed with breakdown of the sandwich structure (X = C5H4SO3H)  

Redox systems of the hexamethylbenzene cluster compounds of niobium and tantalum have been investigated, and reactions of the type 

At high concentrations of mercury(i), however, all the ruthenium(rv) is reduced to ruthenium(iir). In the photochemical oxidation of Hg by Ce in acid perchlorate media it has been suggested that the oxidant species is the one involved in the primary photochemical process. In aqueous solution, or even in the presence of excess cerium(iv), there is no indication of the oxidation of free carbon monoxide. When bound to ruthenium in the cation [Ru(NH3)6CO] +, however, the CO is readily oxidized (in a ten-fold excess of oxidant) to bound CO2. The activation of the bound ligand is considered to derive from its binding to the (H3N)5Ru + centre, but the presence of excess 

In this chapter we have talked about most of the steps in this sequence, except the epoxide-opening reaction (for which read Chapters 17 and 18) and the oxidation step. Which reagent would a chemist choose to oxidize the alcohol to the ketone, and why We shall now move on to look at oxidizing agents in detail. 

We dealt in detail earlier in the chapter with reducing agents and their characteristic chemoselectivi-ties. Oxidizing agents are equally important, and in the chapter on electrophilic addition to alkenes we told you about peracids as oxidizing agents for C=C double bonds—they give epoxides. But 

The most commonly used methods for oxidizing alcohols are based around metals in high oxidation states, often chromium(VI) or manganese(VII), and you will see that mechanistically they are quite similar—they both rely on the formation of a bond between the hydroxyl group and the metal. Another class of oxidations, those that use halogens, sulfur, or nitrogen in high oxidation states, we win deal with relatively briefly. 

We start with this, because overoxidation is difficult. 

Provided the alcohol is not acid-sensitive, a good method is sodium dichromate in dilute sulfuric acid. 

Reduction of these C X a bonds is another example of nucleophilic substitution, in which LiAlHi serves as a source of a hydride nucleophile (H ). Because H is a strong nucleophile, the reaction follows an Sn2 mechanism, illustrated for the one-step reduction of an alkyl halide in Mechanism 12.3. 

The most common oxidizing agents with metal-oxygen bonds contain either chromium in the -1-6 oxidation state (six Cr-O bonds) or manganese in the +1 oxidation state (seven Mn-O bonds). 

Protecting group Structure Protects From Protection Deprotection 

In Chapter 37 you will find out that peracids also react with ketones, but that need not concern us here. 

Lead nitrate Lithium peroxide Magnesium peroxide Strontium nitrate Nickel nitrate 

Nitric acid ( 70% concentration) Perchloric acid ( 60% concentration) 

Lithium hypochlorite Magnesium nitrate Magnesium perchlorate Strontium chlorate Strontium peroxide Zinc chlorate Nitrogen trioxide 

Hydrous Benzoyl Peroxide, USP. Hydrous benzoyl peroxide (Oxy-S. Oxy-IO. Vanoxide) is a while granular powder. In its pure powder form it is explosive. The compound is formulated with. 10% water to make it safer to 

Compounded at, and 10% concentrations, benzoyl p en x-de is both kcraluly tic and kcralogcnic. It is used in the treal-mnl of acnc. Benzoyl peroxide induces proliferation of epi- Jzlial cells, leading to sloughing and repair.  

On the other hand, mild oxidation of mercaptans may result in the formation of disulfides. Thus  

The principal problem involved in oxidation reaction is the induction of the desired reaction coupled with a satisfactory control of the extent of Hreaction. Since this is so, a study of the processes employing oxidation would best be founded on an inspection of the materials and methods used to solve these problems. 

In the case of liquid-phase oxidations, it is possible to use either gaseous oxygen or compounds having oxidizing power. To illustrate the methods that are used, the processes will first be examined from the standpoint of the oxidizing agent, and the character of the action of each agent will be pointed out later by the use of exemplary reactions. A 

The calcium and barium salts have been used for the oxidation of complex proteins. The calcium salt has the advantage in that it forms insoluble products. The calcium oxide combines with the manganese dioxide to form the insoluble CaO Mn02, thus simplifying recovery of products. y Alkaline Solution. When potassium permanganate alone is used in aqueous solution, the solution becomes alkaline through the formation potassium hydroxide  

Three atoms of oxygen are released per molecule of pemianganate, and manganese dioxide in the hydrated form is precipitated. ) 

Cerium(iv).—An attempt has been made to define the mechanism of Ce oxidation of Sn i in the presence of halides. The reaction 

The oxidation of [Fe(gmi)3] + [gmi = glyoxalbis(methylimine)] by Ce in 4.O7M-H2SO4 yields ligand-oxidized complexes or iron i. A first stage has been identified kinetically corresponding to the reaction 

Disproportionation of the Fe complex to observed products occurs subsequently and is discussed in Chapter 2. 

Iron(ni).—Much attention has been given to the reaction between [Fe(CN)6P- and the complex [Co(edta)] -. In the original study, Adamson and Gonick established that a mixed dinuclear complex was formed in the reaction 

In the reactions just described, slow disappearance of the dinuclear complex is also observed with eventual formation of mononuclear products. 

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It gives benzene when heated with soda lime. It is very stable towards oxidizing agents. 

The higher chromium fluorides, CrFstrong oxidizing agents, immediately hydrolysed by water,... 

Chromium trioxide. CrOj. Red precipitate from [Cr04p plus cone. H2SO4, m.p. 198 C, loses oxygen at 420" C. CrOa is a powerful oxidizing agent and is used as such. Acidic, gives [Cr04] - with water. 

Impure C0O2 (oxidizing agent on alkaline Co(ll)) and some mixed oxides of cobalt(lV) and (V), e.g. K.3C0O4, are known. 

Lead(fV) ethanoate, Pb(02CCH3)4, (Pb(ll)ethanoate plus CI2) is a powerful oxidizing agent which will convert vicinal glycols to aldehydes or ketones and 1,2-dicarboxylic acids into alkenes. Primary amides give ketones and amines give nitriles. 

Lead(IV) oxide, PbOj. Chocolate brown (electrolytic oxidation of Pb(II) salts). Used as an oxidizing agent. 

Manganates V f), [MnOJ", permanganates. Dark purple tetrahedral anion (electrolyte oxidation of [Mn04]. Powerful oxidizing agent... 

H0S(0)200S(0)20H. Dibasic acid formed as salts by electrolysis of sulphates at low temperatures and high current density. The acid and persulphates are strong oxidizing agents ( "[S20a] to S04 -t-2 01 volts in acid) but the reactions are often slow. Compare permonosulphuric acid. 

CgHgNa. While crystals m.p. 147 C, b.p. 267"C, darken rapidly in air. Prepared by reducing p-nitroaniline or aminoazobenzene. Oxidizing agents convert it to quinone derivatives, hence it cannot be diazotized with nitric acid. 

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