Abstract: The invention concerns a method for preparing p-hydroxymandelic compounds optionally substituted and their derivatives. More particularly, it concerns a method for preparing p-hydroxymandelic acid and methoxy-3 p-hydroxymandelic acid and their derivatives. The invention concerns a method for preparing p-hydroxymandelic compounds optionally substituted and their derivatives, which consists in condensing in water, in the presence of an alkaline agent, an aromatic compound bearing at least a hydroxyl group and whereof the position in para is free, with glyoxylic acid, said method being characterised in that the reaction is carried out in the presence of an efficient amount of a compound bearing at least two carboxylic functions.

Abstract: The subject of the present invention is a process for the preparation of a 4-hydroxybenzaldehyde carrying at least one substituent in the position ortho to the OH group.It more particularly relates to the preparation of 3-methoxy-4-hydroxybenzaldehyde and of 3-ethoxy-4-hydroxybenzaldehyde.The process for the preparation of a substituted 4-hydroxybenzaldlehyde, substituted at least in the 3 position by an alkoxy group, is characterized in that it comprises subjecting a substituted phenol compound, substituted at least in the 2 position by an alkoxy group and in which the 4 and 6 positions are free, to a first stage of carboxylation in the 6 position, then to a stage of hydroxymethylation in the 4 position, followed by a stage of oxidation of the hydroxymethyl group to a formyl group, and finally to a last decarboxylation stage.

Abstract: Process for preparing chloranil by the oxidative chlorination of a quinone or of a hydroquinone with a hydrochloric acid/hydrogen peroxide mixture, the introduction of hydrogen peroxide being carried out at a temperature above 60.degree. C.

Abstract: Phenolic compounds, notably admixtures of 2,4-dichlorophenol and 2,6-dichlorophenol, are selectively chlorinated at the ortho positions thereof, with gaseous chlorine and in a molten medium, in the presence of a selectivity-enhancing effective amount of an organic cation.

Abstract: Ortho-substituted phenolic compounds, e.g., 2,6-dichlorophenol, are selectively chlorinated, e.g., into 2,4,6-trichlorophenol, with gaseous chlorine in either the molten state or in a solvent medium, in the presence of a selectivity-enhancing effective amount of an organic cation.

Abstract: The chlorophenols, e.g., 2,4,6-trichlorophenol, are efficiently prepared by chlorinating an ortho-/para-substituted phenolic compound with gaseous chlorine, whether in molten state or in a solvent reaction medium, in the presence of a catalytically effective amount of a primary, secondary or tertiary amine.

Abstract: The chloronitrophenols, e.g., 2,6-dichloro-4-nitrophenol (a known agrochemical/pharmaceutical intermediate), are efficiently prepared by chlorinating ortho- or para-nitrophenol with gaseous chlorine, characteristically in the molten state, and in the presence of a catalytically effective amount of a primary, secondary or tertiary amine.