2.4- dinitrophenyl chloride, reaction with hydroxide

A transient also occurs in the reaction of 2,4-dinitrophenyl chloride (3) with sodium hydroxide in aqueous DMSO, Scheme 9.2 [15]. Isomeric a-adducts, 4 and 5, formed relatively rapidly from 3, are cul de sac species and detectable by UV-vis spectroscopy. A slower separate reaction of 3 yields the phenolate, presumably via intermediate 6, which did not accumulate to UV detectable concentrations. 

Dissolve 1 g. (or 0 01 mol) of the phenol in a solution of 0-40 g. of sodium hydroxide in 5 ml. of water. Add the resulting solution to 2-Og. of 2 4-dinitrochlorobenzene dissolved in 30 ml. of 95 per cent, ethanol add more alcohol, if necessary, to effect solution. Heat the solution under reflux on a water bath until the colour (usually red) is discharged and a copious precipitate of sodium chloride appears (30-60 minutes). Dilute the reaction mixture with an equal volume of water, filter off the precipitated 2 4-dinitrophenyl ether, wash with water, and recrystallise from alcohol. 

Oryzalin is prepared by a different route. Synthesis starts with chlorobenzene, which is nitrated in a single step into potassium 4-chIoro-3,5-dinitrobenzene sulfonate (I). This is then converted with phosphorus oxychloride and phosphorus pentachloride into 4-chloro-3,5-dinitrobenzene sulfonyl chloride (II). The reaction of the latter with dipropylamine gives 4-dipropylamino-3,5-dinitrophenyl sulfonyl chloride (III), the reaction of which with ammonium hydroxide yields oryzalin. 

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