Chemistry: electrical and wave energy – Processes and products – Processes of treating materials by wave energy
Patent
1989-03-20
1992-03-03
Niebling, John
Chemistry: electrical and wave energy
Processes and products
Processes of treating materials by wave energy
2041581, C07C 1700
Patent
active
050929712
ABSTRACT:
Selective bromination of alkylarenes to the alpha monobrominated derivative is desirable as a precursor for the selective production of, for example, the corresponding alcohols. The product can be obtained by a photolytic reaction between the substrate, hydrogen peroxide and hydrogen bromide in approximately equimolar ratios in an organic solvent, but improvement in the yield of the product coupled with similar or improved selectivity in its production was either not achieved or was actually impaired by a range of variations in the ratios and by omitting the solvent.
The invention employs mole ratios of H.sub.2 O.sub.2 :substrate of 0.1:1 to 0.4:1, preferably 0.2:1 to 0.33:1 and of H.sub.2 O.sub.2 :bromide of 1:1.2 to 1:2, preferably about 1:1.3 to 1:1.8 and progressive introduction of the H.sub.2 O.sub.2, either in the presence or absence of the solvent, while irradiating with light preferably having principal emissions in the range of 250 to 600 nm, and the process thereby achieves either or both of improved yield and improved selectivity of the alpha monobrominated product. The reaction mixture is preferably maintained at 50.degree. to 70.degree. C. The process is especially suitable for deactivated alkylarenes, such as o-nitrotoluene.
REFERENCES:
patent: 3492211 (1970-01-01), Pochowicz
patent: 3947336 (1976-03-01), Clark
patent: 4165268 (1979-08-01), Marti
patent: 4191621 (1980-03-01), Riethmann
Kharasch et al, Journal of Organic Chemistry, vol. 3, pp. 33-47, 1938.
Jeff Martin
Turner Philip J.
Interox Chemicals Limited
Marquis Steven P.
Niebling John
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