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products of the substitution of nitro groups, —NO2, for the hydrogen atoms in the phenol ring, C6H5OH. The nitrophenols shown in Table 1 are of commercial significance.

Table 1. Properties of commercial nitrophenols
 Melting pointC)Density (g/cm3)
*Temperature (°C)
o-Nitrophenol...................44.91.29 (40)*
p-Nitrophenol...................1141.48 (20)
2,4-Dinitrophenol.................1131.68 (24)
2,4,6-Trinitrophenol ...............122.51.76(20)

Nitrophenols are crystalline substances. In industry, ortho- and para-nitrophenols are produced by heating the corresponding nitrochlorobenzenes with an aqueous solution of sodium hydroxide; 2,4-dinitrophenol (2,4-D) is obtained in an analogous manner from 2,4-dinitrochlorobenzene. These nitrophenols are blood poisons, but they also act on the nervous system and irritate the mucous membranes and skin, leading to dermatitis and chronic eczema. For example, the maximum permissible concentration of 2,4-D in air in work areas is 0.05 mg/m3. The main use of ortho- and para-nitrophenols is in the production of ortho- and para-aminophenols. Picric acid, sulfur black dye, and 2,4-diaminophenol (amidol developer) are produced from 2,4-D; it is also used as a herbicide.

Picric acid, or 2,4,6-trinitrophenol (2,4,6-T), was used as a yellow dye for silk (the first synthetic organic dye) and as an explosive (melinite and lyddite); it is poisonous, and its maximum permissible concentration in air in work areas is 1 mg/m3. With metals, 2,4,6-T forms dangerously explosive, easily flammable salts called picrates.


Orlova, E. Iu. Khimiia i tekhnologiia brizantnykh vzryvchatykh ve-shchestv, 2nd ed. Leningrad, 1973.


References in periodicals archive ?
Moreover, nitrophenols and methylphenol sources have been related to vehicular emissions [6,7] Phenols may occur naturally via biodegradation of humic products, for example tannins and lignins [8].
Nitrophenol compounds have wide applications in various medical, chemical, and poison production industries.
Exposure of the general population to nitrophenol isomers is mainly through ambient air and drinking water.
The release of p- nitrophenol was measured at 405 nm from a p- nitrophenol standard curve.
A solution of 4-nitrophenol in buffer was used to determine the molar absorptivity of the nitrophenol produced by the hydrolysis of paraoxon; the molar absorptivity at 405 nm (pH 8.
The retention of nitrophenol isomers was even stronger and a mixture of methanol and water (80/20) was used to get the following capacity factors k' for both sorbents: o-nitrophenol--1.
Enzymatic activity of alkaline phosphatases at various concentrations of Naja naja karachiensis venom in terms of para- nitrophenol (PNP) released.
The amount of nitrophenol released was determined by comparison with a standard nitrophenol curve and expressed as [micro]mol/30 min/mg protein.
This mixture was incubated at 37 oC for 30 minutes and liberated para nitrophenol was recorded at 410 nm.
The assay was based on monitoring the production of yellow colored p- nitrophenol (lmax = 400 nm) from bis-(p-nitrophenyl) phosphate by NPPI action [39].
One unit of enzyme is defined as the amount of enzyme required to release 1 umol of p- nitrophenol per min.