Acetone, bromination hydrogenation

Oxidations usually proceed in the dark at or below room temperature in a variety of solvents ranging from aqueous bicarbonate to anhydrous benzene-pyridine. Base is quite commonly used to consume the hydrogen halide produced in the reaction, as this prevents the formation of high concentrations of bromine (or chlorine) by a secondary process. The reaction time varies from a few minutes to 24 hours or more depending on the nature of the reagent and the substrate. Thus one finds that NBS or NBA when used in aqueous acetone or dioxane are very mild, selective reagents. The rate of these oxidations is noticeably enhanced when Fbutyl alcohol is used as a solvent. In general, saturated, primary alcohols are inert and methanol is often used as a solvent. 

Acetone Acetylene Alkali and alkaline earth metals, e.g. sodium, potassium, lithium, magnesium, calcium, powdered aluminium Anhydrous ammonia Concentrated nitric and sulphuric acid mixtures Chlorine, bromine, copper, silver, flourine or mercury Carbon dioxide, carbon tetrachloride, or other chlorinated hydrocarbons. (Also prohibit, water, foam and dry chemical on fires involving these metals - dry sand should be available.) Mercury, chlorine, calcium hypochlorite, iodine, bromine or hydrogen fluoride... 

Bromine trifluoride Solvents Chromium trioxide Acetone Chromyl chloride Organic solvents Dioxygen difluoride Various materials Hydrogen peroxide Acetone... 

Its solutions in dilute hydrobromic acid are a carmine-red (0.025 M PoBr4) and in more dilute solution (10 3 M), orange red. The tetrabromide is soluble in ethanol, acetone and some other ketones, and is sparingly soluble in liquid bromine. It is hygroscopic and is easily hydrolyzed to a white, basic bromide of variable composition. It forms a yellow ammine in ammonia gas and this yields polonium dibromide and polonium metal on standing, presumably because of radiation decomposition of the ammonia and subsequent hydrogen reduction of the tetrabromide (7). 

A. 2,4-Dibromo-3-pentanone (1). A three-necked, 250-ml. flask is fitted with a stirrer, a dropping funnel, and a condenser protected by a calcium chloride drying tube. Bromine (160 g., 1 mole) is added rapidly to a stirred solution of 45 g. (0.52 mole) of 3-pentanone (Note 1) and 1 ml. of phosphorus tribromide maintained between —10° and 0° with a dry ice-acetone bath in an efficient hood. Toward the end of the reaction very large amounts of hydrogen bromide are evolved, and the rate of addition must be controlled to allow the hood to exhaust the gas. Alternatively, a... 

When the chlorine in the first-mentioned preparation of tetrachloroselenophene is replaced by bromine, a vigorous reaction occurs and hydrogen bromide is liberated. After twenty-four hours the solution is washed with dilute sodium hydroxide solution and with water, then evaporated on the water-bath. The brown residue, after crystallisation from alcohol, gives the tetrabromo-compound as a white, finely crystalline substance, M.pt. 102° C., wThich does not reduce permanganate in acetone solution, but slowly deposits selenium on boiling with water. 

NIOSH REL (Chromium(VI)) TWA 0.025 mg(Cr(VI))/mh CL 0.05/15M SAFETY PROFILE Confirmed human carcinogen. Poison by subcutaneous route. Mutation data reported. A powerful oxidizer. A powerful irritant of skin, eyes, and mucous membranes. Can cause a dermatitis, bronchoasthma, chrome holes, damage to the eyes. Dangerously reactive. Incompatible with acetic acid, acetic anhydride, tetrahydronaphthalene, acetone, alcohols, alkali metals, ammonia, arsenic, bromine penta fluoride, butyric acid, n,n-dimethylformamide, hydrogen sulfide, peroxyformic acid, phosphorus, potassium hexacyanoferrate, pyridine, selenium. 

A powerful oxidizer. Explosive reaction with acetaldehyde, acetic acid + heat, acetic anhydride + heat, benzaldehyde, benzene, benzylthylaniUne, butyraldehyde, 1,3-dimethylhexahydropyrimidone, diethyl ether, ethylacetate, isopropylacetate, methyl dioxane, pelargonic acid, pentyl acetate, phosphoms + heat, propionaldehyde, and other organic materials or solvents. Forms a friction- and heat-sensitive explosive mixture with potassium hexacyanoferrate. Ignites on contact with alcohols, acetic anhydride + tetrahydronaphthalene, acetone, butanol, chromium(II) sulfide, cyclohexanol, dimethyl formamide, ethanol, ethylene glycol, methanol, 2-propanol, pyridine. Violent reaction with acetic anhydride + 3-methylphenol (above 75°C), acetylene, bromine pentafluoride, glycerol, hexamethylphosphoramide, peroxyformic acid, selenium, sodium amide. Incandescent reaction with alkali metals (e.g., sodium, potassium), ammonia, arsenic, butyric acid (above 100°C), chlorine trifluoride, hydrogen sulfide + heat, sodium + heat, and sulfur. Incompatible with N,N-dimethylformamide. 

The direct bromination of aliphatic ketones occurs readily, often giving isomeric mixtures. Thus, methyl ethyl ketone and an equimolar quantity of bromine yield the a-btomomethyl (17%) and the a-bromoethyl (50%) isomers polybrominated products are also formed. On the other hand, only the tertiary hydrogen in methyl isopropyl ketone is substituted upon monobromination. By varying the conditions for the bromination of acetone, mono- or poly-substitution products may be formed e.g., bromo-acetone (44%), a,a -dibromoacetone (60%), and a,a,a -tribromoacetone (60%). ... 

Concentrated h3alrogen halides or oxyacids also decompose the base, immediateh, giving acetone and a mercuric salt. Bromine in potassium bromide Avith the base yields mercuric bromide and 6 -dibromoacetone whilst hydrogen sulphide precipitates mercuric sulphide from the base. 

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