Chromium oxidizing agent

Many oxidants, especially the older and stronger chromium oxidizing agents, may have their reactivity and selectivity modified by adsorption on to inert supports.Reactions utilizing supported oxidants have the advantage that the residual chromium salts remain bound to the support and thus work-up often becomes reduced to a mere filtration. Many of these systems are discussed in detail later (Volume 7, Chapter 7.3). 

Precaution Powerful oxidizer mixt. with boron burns violently if ignited Uses Rust-inhibitive pigment for paints corrosion inhibitor mfg. of chromium oxidizing agent depolarizer for batteries coating for light metal... 

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. 

All compounds of chromium are colored the most important are the chromates of sodium and potassium and the dichromates and the potassium and ammonium chrome alums. The dichromates are used as oxidizing agents in quantitative analysis, also in tanning leather. 

In order to circumvent this problem, there has been significant activity directed toward the search for a less environmentally toxic and more selective oxidizing agent than chromium. For example, Hoechst has patented a process which uses organorhenium compounds. At a 75% conversion, a mixture of 86% of 2-methyl-l,4-naphthoquinone and 14% 6-methyl-l,4-naphthoquinone was obtained (60). Ceric sulfate (61) and electrochemistry (62,63) have also been used. 

Fire Hazards - Flash Point Not flammable Flammable limits in Air (%) Not flammable Fire Extinguishing Agents Not pertinent Fire Extinguishing Agents Not To Be Used Not pertinent Special Hazards cf Combustion Products Toxic chromium oxide fiunes may fom in fires Behavior in Fire Can increase the intensity of fires when in contact with combustible materials Ignition Temperature Not pertinent Electrical Hazard Not pertinent Burning Rate Not pertinent. 

The composition of this alloy (54% nickel, 15% molybdenum, 15% chromium, 5% tungsten and 5% iron) is less susceptible to intergranular corrosion at welds. The presence of chromium in this alloy gives it better resistance to oxidizing conditions than the nickel/molybdenum alloy, particularly for durability in wet chlorine and concentrated hypochlorite solutions, and has many applications in chlorination processes. In cases in which hydrochloric and sulfuric acid solutions contain oxidizing agents such as ferric and cupric ions, it is better to use the nickel/molybdenum/ chromium alloy than the nickel/molybdenum alloy. 

Most other oxidizing agents, such as chromium trioxide (0rO3) in aqueous acid, oxidize primary alcohols directly to carboxylic acids. An aldehyde is involved as an intermediate in this reaction but can t usually be isolated because it is further oxidized too rapidly. 

In the laboratory, acidified solutions of dichromates, in which the oxidation number of chromium is +6, are useful oxidizing agents ... 

Chromate conversion coatings for aluminum are carried out in acidic solutions. These solutions usually contain one chromium salt, such as sodium chromate or chromic acid and a strong oxidizing agent such as hydrofluoric acid or nitric acid. The final film usually contains both products and reactants and water of hydration. Chromate films are formed by the chemical reaction of hexavalent chromium with a metal surface in the presence of accelerators such as cyanides, acetates, formates, sulfates, chlorides, fluorides, nitrates, phosphates, and sulfamates. 

Various oxidizing agents based on chromium(VI) have been used to oxidize 2° alcohols to ketones. 

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