Phenols dinitrophenyl ethers

Dinitrophenyl ethers. 2 4-Dinitrochlorobenzene reacts with the sodium salts of phenols to yield crystalline 2 4-dinitrophenyl ethers ... 

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. 

Dinitrofluorobenzene (DNFB) reacts with phenols and, which is not of interest here, with amino groups. Hydrogen fluoride is eliminated. DNFB does not react w ith carboxylic acids. Alcohols, if they react at all, form dinitrophenyl ethers very slowly. Very weakly dissociated phenolic hydroxyl groups, e.g., in salicylic acid (pK = 13.4), are inert towards DNFB. 

R Lauren, MP Agnew. Determination of 2,4-dinitrophenyl ether derivatives of the phenolic metabolites of carbofuran by high-performance liquid chromatography. J Chromatogr 292 439-443, 1984. 

M. Lehtonen, Gas chromatographic determination of phenols as 2,4-dinitrophenyl ethers using glass capillary columns and an electron capture detector, J. Chromatogr., 202 413-421 (1980). 

A high ECD response is also provided by 2,4-dinitrophenyl ethers, for which various methods of preparation were reported by Cohen et al. [63]. A 4-ml volume of acetone containing phenols (ca. 10 yjg), 0.1 ml of a saturated methanolic solution of sodium methanolate and 1 ml of l-fluoro-2,4-dinitrobenzene in acetone (1%, w/v) were refluxed in a 10-ml flask for 30 min. The reaction mixture was then added to 25 ml of sodium hydroxide solution (2.5%, w/v), diluted with a small volume of water and extracted with 25 ml of chloroform. After being dried with anhydrous sodium sulphate, the extract was carefully evaporated and the residue was dissolved in acetone and injected into the chromatograph. 

Characterizotian of hydroxy compounds. The reagent reacts with phenols in acetone solution under catalysis by triethylamine to form 2,4-dinitrophenyl ethers useful for identification. Under similar conditions it affords solid derivatives of alcohols. ... 

GAS CHROMATOGRAPHIC RETENTION AND ELECTRON-CAPTURE RESPONSE FOR PENTA-FLUOROBENZYL (PFB), 2.6-DINITRO-4-TRIFLUOROMETHYLPHENYL (DNT) AND 2,4-DINITROPHENYL (DNP) ETHERS OF PHENOLS [20]... 

If the other product from the hydrolysis is phenol, the procedures described in Section 5.1 are applied to the preparation of the derivatives, particularly those which permit a very sensitive analysis. Perfluorinated acyl derivatives and 2,4-dinitrophenyl-, 2,6-dinitro-4-trifluoromethylphenyl and pentafluorophenyl ethers are frequently used [482], when concentrations of 0.01—0.1 ppb of the insecticide in water can be determined. 

Arylations are commoner than alkylations. Ullmann and Nadai s preparation of dinitrochlorobenzenes, and its extension to that of diphenyl ethers—reactions in which the nucleophiles are chloride ions and phenols, respectively—have been mentioned already (p. 268). Applied to l-(2,4-dinitronaphthyl)pyridinium chloride, the reaction gives l-chloro-2,4-dinitronaphthalene, and the same salt reacts with water to give the naphthol, with hydrogen sulphide to yield the thionaphthol, and with carboxylic acids to form dinitronaphthyl esters . Amines , alcohols , mercaptans and thiophenols have been dinitrophenylated with pyridinium salts. Styrylpyridinium salts give N-styrylpiperidine with piperidine . 

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