2,4-Dinitrophenols

Dinitrophenol may be readily prepared by taking advantage of the great reactivity of the chlorine atom in 2 4-dinitro-l-chlorobenzene ... 

In a 1 htre round bottomed flask equipped with a reflux condenser place a solution of 62 -5 g. of anhydroas sodium carbonate in 500 ml. of water and add 50 g. of commercial 2 4-dinitro-l-chlorobenzene. Reflux the mixture for 24 hours or until the oil passes into solution. Acidify the yellow solution with hj drochloric acid and, when cold, filter the crystaUine dinitrophenol which has separated. Dry the product upon filter paper in the air. The yield is 46 g. If the m.p, differs appreciably from 114°, recrystallisc from alcohol or from water. 

RCH(OH)=CHCOR or -keto esters RCH(OH)=CHCOOR ) dissolve in dilute sodium hydroxide solution, i.e., contain an acidic group of sufficient strength to react with the alkah. Carboxyhc acids and sulphonic acids are soluble in dilute solutions of sodium bicarbonate some negatively-substituted phenols, for example, picric acid, 2 4 6-tribromo-phenol and 2 4-dinitrophenol, are strongly acidic and also dissolve in dilute sodium bicarbonate solution. 

Group III. Carboxylic and sulphonic acids (also sym.-tribromophenol, 2 4-dinitrophenol and picric acid) are also soluble in dilute sodium bicarbonate solution. 

The nitration of anisole in 40% aq. nitric acid in the presence of some nitrous acid yielded 2,4-dinitrophenol as the main product. In more concentrated solutions of nitric acid 0- and />-nitroanisoles were the main products, less than o-1 % of the weta-isomer being formed. " The isomeric ratios for nitration imder a variety of conditions are given later ( 5.3.4). 

Dinitrophenol (indicator) dissolve 0.1 g in a few mL alcohol, then dilute with water to 100 mL pH range colorless 2.6-4.0 yellow. 

Peroxyoxalate chemiluminescence is the most efficient nonenzymatic chemiluminescent reaction known. Quantum efficiencies as high as 22—27% have been reported for oxalate esters prepared from 2,4,6-trichlorophenol, 2,4-dinitrophenol, and 3-trif1uoromethy1-4-nitropheno1 (6,76,77) with the duorescers mbrene [517-51-1] (78,79) or 5,12-bis(phenylethynyl)naphthacene [18826-29-4] (79). For most reactions, however, a quantum efficiency of 4% or less is more common with many in the range of lO " to 10 ein/mol (80). The inefficiency in the chemiexcitation process undoubtedly arises from the transfer of energy of the activated peroxyoxalate to the duorescer. The inefficiency in the CIEEL sequence derives from multiple side reactions available to the reactive intermediates in competition with the excited state producing back-electron transfer process. 

Up until 1986 the major use for 2-j -butylphenol was in the production of the herbicide, 2-j -butyl-4,6-dinitrophenol [88-85-7] which was used as a pre- and postemergent herbicide and as a defoHant for potatoes (30). The EPA banned its use in October 1986 based on a European study which showed that workers who came in contact with 2-j -butyl-4,6-dinitrophenol experienced an abnormally high rate of reproduction problems. Erance and the Netherlands followed with a ban in 1991. A significant volume of 2-j -butyl-4,6-dinitrophenol is used worldwide as a polymerization inhibitor in the production of styrene where it is added to the reboiler of the styrene distillation tower to prevent the formation of polystyrene (31). OSBP is used in the Par East as the carbamate derivative, 2-j -butylphenyl-Ai-methylcarbamate [3766-81-2] (BPMC) (32). BPMC is an insecticide used against leaf hoppers which affect the rice fields. 

Amino-4-nitropheno1 is produced commercially by the partial reduction of 2,4-dinitrophenol This reduction may be achieved electrolyticaHy using vanadium (159) or chemically with polysulftde, sodium hydrosulftde, or hydrazine and copper (160). Alternatively, 2-acetamidophenol or 2-methylbenzoxazole may be nitrated in sulfuric acid to yield a mixture of 4- and 5-nitro derivatives that are then separated and hydrolyzed with sodium hydroxide (161). 

Amino-4,6-dinitrophenol. This derivative (10), also known as picramic acid, forms dark red needles from ethanol and prisms from... 

Polysulfide Melt. Cl Sulfur Black 1 [1326-82-5] (Cl 53185), derived from 2,4-dinitrophenol, is the most important dye in this group which also includes the indophenol-type intermediates. The latter are appHed in the stable leuco form. The derived dyes are usually confined to violet, blue, and green shades. Other members of this group are intermediates capable of forming quinoneimine (10) or phenazone stmctures (11) that produce red-brown or Bordeaux shades ... 

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