Rhone-Poulenc Specialites Chimiques

Rhone-Poulenc Chimie

Jean-Luc Bougeois

Serge Ratton

Jean-Pierre LeCouve

Michel Baudouin

Nitrophenols, in an isomer ratio para-nitrophenol/ortho-nitrophenol of at least 55/45, are continuously and directly prepared in steady state, by (a) establishing, in a confined reaction zone, an aqueous reaction solution including from 5% to 40% by weight of nitric acid, from 5% to 40% by weight of nitrous acid relative thereto, and an amount of nitrophenols within the limits of the solubility thereof in such reaction solution, (b) continuously introducing and reacting phenol and nitric acid into and with such reaction solution, at a rate of about 0.5 to 2.0 moles of nitric acid per mole of phenol, (c) maintaining the temperature in such confined reaction zone at a value ranging from about 10.degree. to about 40.degree. C. during such reaction, and (d) continuously withdrawing from such confined reaction zone admixture of para-nitrophenol and ortho-nitrophenol, in an isomer ratio para-nitrophenol/ortho-nitrophenol of at least 55/45.

Continuous direct preparation of nitrophenols

Substituted bromobenzaldehydes, e.g., 5-bromovanillin, are facilely prepared without conjoint production of HBr, by brominating the corresponding benzaldehydes with a brominating agent couple which comprises hydrobromic acid and a bromide ion oxidizer.

Bromination of substituted benzaldehydes

Substituted bromobenzaldehydes, e.g., 5-bromovanillin, are facilely prepared with overall avoidance of HBr by-product, by (i) first brominating the corresponding benzaldehyde with a less than stoichiometric amount of bromine, and (ii) completing said bromination reaction with a brominating couple which comprises (1) the hydrobromic acid generated in situ in the step (i) and (2) a bromide ion oxidizer.

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Sainte Foy Les Lyon, France

Jean-Luc Bougeois