Nitrophenols


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Nitrophenols

 

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.

REFERENCE

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

D. A. GUREVICH

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Clinical symptoms related to poisons with nitrophenols are similar to that exerted by chlorophenols.
Mutagenic influence was also exerted by nitrophenols and nitrated aminophenols.
lethal doses (lD50) of nitrophenol orally administrated to rats and mice are 450-850 mg/kg and 380 mg/kg of body weight, respectively, and for dinitrophenol (rats) only 30 mg/kg of bodyweight [35].
The presence of nitrophenols in the environment is related both to natural processes and anthropogenic activity.
Nitrophenols are formed by man during production and degradation of pesticides like 2-buthyl-4,6-dinitrophenol (Dinoseb) and 4,6-dinitro-2-methylphenol (DNoc).
A daily uptake by inhalation of nitrophenols was calculated to be of 0.
Oxidation of nitrophenols with ozone and ozone combined with hydrogen peroxide and/or UV radiation was also studied by Trapido et al.
Degradation of nitrophenols by ozone combined with UV-radiation and hydrogen peroxide.
According to the results obtained by our earlier studies [28] the degradation rates of some other nitrophenols in the Fenton reaction were significantly higher when relatively higher [Fe.
Degradation of nitrobenzene and nitrophenols by means of advanced oxidation processes in a homogeneous phase: Photolysis in the presence of hydrogen peroxide versus the Fenton reaction.
A mixture of ozone gas and air produced by a laboratory ozone generator was bubbled through the aqueous solution of nitrophenol.