US EPA

8581891 

Journal Article 

The significance of the bromine cation in aromatic substitution. Part II. Preparative applicability 

Derbyshire, DH; Waters, WA 

1950 

Yes 

Journal of the Chemical Society
ISSN: 0368-1769 

573-577 

English 

10.1039/jr9500000573 

https://www.scopus.com/inward/record.uri?eid=2-s2.0-37049146230&doi=10.1039%2fjr9500000573&partnerID=40&md5=e846c9c1cfd03c4ab3aabaf38669054f
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Acid solutions of hypobromous acid contain a very much higher concentration of bromine cations than do acid solutions of free bromine. Highly reactive solutions containing bromine cations can be made by adding mercuric or silver salts gradually to solutions of bromine in water or acetic acid in the presence of either nitric or sulphuric acid. Benzene, chlorobenzene, bromobenzene, and p-dibromobenzene can be brominated with such mixtures in 2N-nitric acid; benzoic acid and methyl benzoate require a stronger nitric acid solution, whilst nitrobenzene, 2:4-dinitrotoluene, and m-dinitrobenzene need 90% sulphuric acid. The expected aromatic bromination products have been isolated from these substances in 60-80% yield. Bromine cations can also be formed by adding potassium bromate to acid solutions of bromine, and these mixtures too constitute active brominating agents. Acetic and propionic acids, methyl alcohol, and dioxan all resist attack by bromine cations in 2N-mineral acid. The experimental evidence substantiates the polar-activation theory of aromatic substitution.