Silver, reaction with bromine

The procedure described here allows for a convenient and efficient preparation in very high yields of large quantities of bromides from carboxylic acids containing an olefinic functionality. The Hunsdiecker reaction is traditionally accomplished by treating anhydrous silver carboxylates with bromine or iodine.2 Heavy metal salts such as mercury,3 lead,4 and thallium5 have also been used successfully as well as tert-butyl hypoiodite.6 The major disadvantages associated with the above methods, such as use of heavy metal salts and non-tolerance towards olefins, has led to the development of a more versatile method using O-acyl thiohydroxamates.7 8 The O-... 

Ag2Se (c, II). Fabre2 measured the heats of reaction of silver selenide with bromine water and of aqueous silver acetate with gaseous hydrogen selenide. See also Pelabon1 and Tubandt and Reingold.1... 

A strong base. Vigorous reaction with 1,2,4,5-tetrachlorobenzene has caused many industrial explosions and forms the extremely toxic 2,3,7,8-tetrachlorodibenzodioxin. Mixmres with aluminum + arsenic compounds form the poisonous gas arsine. Potentially explosive reaction with bromine, 4-chlorobutyronitrile, 4-chloro-2-methylphenol (in storage), nitrobenzene + heat, sodium tetrahydroborate, 2,2,2-trichloroethanol, zirconium + heat. Reacts to form explosive products with ammonia + silver nitrate (forms silver nitride), N,N -bis(trinitroethyl)urea (in storage), cyanogen... 

The conversion of 5a-cholestan-6/5-ol into the 6yS, 19-epoxide, by reaction with bromine and silver oxide, has been improved by the use of certain silver salts with bromine in pentane, in the dark. Silver acetate, carbonate, and... 

ARSENIC (7440-38-2) Finely divided material forms explosive mixture with air. Decomposes on contact with acids or acid fumes, emitting fumes of arsenic. Contact of dust or powder with strong oxidizers can cause ignition or explosion. Violent reaction with bromine azide, bromine pentafluoride, bromine trifluoride, dichlorine oxide, hypochlorous acid, nitrogen trichloride, tribromamine hexaammoniate, nitrogen oxyfluoride, potassium chlorate, potassium dioxide, powdered rubidium, silver fluoride. Incompatible with strong acids, cesium acetylene carbide, chromic acid, chromium trioxide, hafnium, halogens, lead monoxide, mercury oxide, nitryl fluoride, platinum, potassium nitrate, silver nitrate, sodium chlorate, powdered zinc. 

AZIDA SODICA (Spanish) (26628-22-8) Reacts with hot water. Explosive decomposition in elevated temperatures above 525°F/274°C. Forms ultra-sensitive explosive compounds with heavy metals copper, copper alloys, lead, silver, mercury, carbon disulfide, trifluoroacryloyl fluoride. Violent reaction with acids, forming explosive hydrogen azide. Violent reaction with bromine, barium carbonate, chromyl chloride, dimethyl sulfate, dibromomalononitrile. Incompatible with caustics, cyanuric chloride, metal oxides, metal sulfides, methyl azide, phosgene. 

Precaution Incompat. with alkalis and their carbonates, lead and silver salts explosive reaction with potassium chlorate or bromine trifluoride violent reaction with bromine pentafluoride, NH4, NO3, IF7... 

Toxicotogy ACGIH TLV/TWA10 mg/m STEL 20 mg/m LD50 (oral, rat) 1650 mg/ kg, (IP, mouse) 1439 mg/kg LDLo (IV, rabbit) 78 mg/kg poison by subcutaneous, IV and intramuscular routes severe eye irritant mutation data TSCA listed Precaution Incompat. with alkalis and their carbonates, lead and silver salts explosive reaction with potassium chlorate or bromine trifluoride violent reaction with bromine pentafluoride, NH4, NO3, IFj... 

Alkyl fluorides have been prepared by reaction between elementary fluorine and the paraffins, by the addition of hydrogen fluoride to olefins, by the reaction of alkyl halides with mercurous fluoride, with mercuric fluoride, with silver fluoride, or with potassium fluoride under pressure. The procedure used is based on that of Hoffmann involving interaction at atmospheric pressure of anhydrous potassium fluoride with an alkyl halide in the presence of ethylene glycol as a solvent for the inorganic fluoride a small amount of olefin accompanies the alkyl fluoride produced and is readily removed by treatment with bromine-potassium bromide solution. Methods for the preparation of alkyl monofluorides have been reviewed. ... 

Silver carboxylates 1 can be decarboxylated by treatment with bromine, to yield alkyl bromides 2 in the so-called Hunsdiecker reaction. ... 

Suitable substrates for the Hunsdiecker reaction are first of all aliphatic carboxylates. Aromatic carboxylates do not react uniformly. Silver benzoates with electron-withdrawing substituents react to the corresponding bromobenzenes, while electron-donating substituents can give rise to formation of products where an aromatic hydrogen is replaced by bromine. For example the silver /)-methoxybenzoate 6 is converted to 3-bromo-4-methoxybenzoic acid 7 in good yield ... 

The Hunsdiecker reaction is the treatment of the dry silver salt of a carboxylic acid with bromine in carbon tetrachloride. Decarboxylation occurs, and the product isolated is the corresponding organic bromide 16). Since dry silver salts are tedious to prepare, a modification of the reaction discovered by Cristol and Firth (77) is now... 

With bromine monochloride at 0°C in a variety of solvents, 1 was converted into addition products, the product distribution being a function of solvent. A change in halogenating agent also altered the product ratio. (Scheme 4) Nucleophilic displacement reactions between these products and silver fluoride was found to cause preferential bromine substitution (83G149). 

Reactions in acetic anhydride with metal acetates present probably occur by 1,4-addition of bromonium acetate (85CHE458). When NBS in sulfuric acid at 20°C was used, the product ratio resembled that observed with bromine-sulfuric acid-silver sulfate. At 60°C the ratio changed to 2 1.2 1 as a consequence of more extensive dibromination (88CHE892) (Scheme 33). As might have been deduced, 2-(2 -thienyl)quinoline was brominated only in the thiophene ring (82CHE28). 

---