Bromine, atomic weight preparation

In 1897-1899, the work of Richards and Baxter4 on the atomic weight of cobalt was published. Anhydrous cobaltous bromide was prepared by direct union of the pure elements and the product sublimed in a stream of hydrogen bromide and nitrogen. The bromine in the salt was determined by the two usual methods, the amount of silver required to precipitate it being first measured and then the precipitated silver bromide being collected and weighed. The final results were as follow ... 

Prepare a table showing the relation between chlorine, bromine, and iodine. The table should include the atomic weight, physical state, color, typical method of preparation, properties, and analogous compounds. 

After the development of catalyst-transfer condensation polymerization of polythiophene, the block copolymer of polythiophene and poly(alkyl acrylate) was prepared more easily. Vinyl-terminated polythiophene was first prepared. The vinyl group was converted to the 2-hydroxyethyl group by hydroboration, followed by esterification with 2-bromopropionyl bromide to give a macroinitiator for ATRP (Scheme 50) [142]. The allyl-terminated polythiophene was also converted to a macroinitiator for ATRP, which led to block copolymers of polythiophene and poly (aUcyl methacrylate) [143] or poly(acrylic acid) [144]. This allyl-terminated polythiophene has a bromine atom at the other end, which has an adverse effect on the purity of block copolymers prepared by ATRP. Hawker, Kim, and coworkers reported that replacement of the bromine with a phenyl group, followed by functionalization of the allyl group for the ATRP initiator unit, allowed access to narrower molecular weight distribution diblock copolymers of polythiophene and ATRP-derived vinyl block [145]. 

Silver salts of carboxylic acids react with bromine or chlorine in an inert solvent to give carbon dioxide, a silver halide, and the halide containing one less carbon atom than the acid. The method has been reviewed. " Both low- and high-molecular-weight aliphatic bromides have been prepared. "t i i The degradation of silver salts of aromatic acids is complicated by nuclear halogenation." The procedure is valuable as a step in the synthesis of oi-bromo esters (C, to C,) from dicarboxylic acids. ... 

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