Para-nitrophenol

A brief account of aromatic substitution may be usefully given here as it will assist the student in predicting the orientation of disubstituted benzene derivatives produced in the different substitution reactions. For the nitration of nitrobenzene the substance must be heated with a mixture of fuming nitric acid and concentrated sulphuric acid the product is largely ni-dinitrobenzene (about 90 per cent.), accompanied by a little o-dinitrobenzene (about 5 per cent.) which is eliminated in the recrystallisation process. On the other hand phenol can be easily nitrated with dilute nitric acid to yield a mixture of ortho and para nitrophenols. It may be said, therefore, that orientation is meta with the... 

Commercial Mononitrophenol. Yel cryst mass mp about 45° mostly ortho- with some para-nitrophenol. Can be prepd by the nitration of phenol with dil nitric acid (1 3) at a temp below 35° (see Ref, p 283). Although it does not possess expl properties and does not gelatinize NC, it has been used as the fuel component of some commercial expls. It forms salts, some of which are weak expls which were used in expl compns, for example, Voight Explosives (qv)... 

Esteban E, Rubin C, Hill R, et al. 1996. Association between indoor residential contamination with methyl parathion and urinary para-nitrophenol. J Expo Anal Environ Epidemiol 6 375-387. 

Brooks JD, Riviere JE. 1996. Quantitative percutaneous absorption and cutaneous distribution of binary mixtures of phenol and para-nitrophenol in isolated perfused porcine skin. Fundam Appl Toxicol... 

Ortho and para nitrophenols are more acidic than phenol. Draw the resonance structures of the corresponding phenoxlde ions. 

Buffer solution, double strength - add to 4.5 I water, 400 g oven-dried calcium acetate, 80 g 4-nitrophenol and 6 g of light magnesium oxide. [Safety note 4- (or para-) nitrophenol may cause eye irritation or irreversible eye injury, and may be harmful by absorption through skin or ingestion.] Heat the mixture to dissolve the solids and dilute to 5 I. Filter if the solution is not clear. The pH of this solution should lie between 6.9 and 7.1 adjust by the addition of hydrochloric acid or magnesium oxide as necessary. 

Among the nitrophenols, meta- and para-nitrophenols have high boiling points because of intermolecular hydrogen bonding, as shown below. 

Intermolecular hydrogen bonding of para-nitrophenol with water... 

Phenol, when treated with dilute nitric acid at room temperature, forms ortho- and para-nitrophenol. 

There are occasions in which death is undoubtedly due to a pesticide, and yet the chemical analysis fails to reveal its presence or shows only insignificant traces. This may be due to the rapid metabolic conversion of the particular pesticide. This is the case with parathion which is rapidly converted to para-nitrophenol due to in vivo hydrolysis. Pesticides, especially those that are comparatively less toxic to mammals, such as dichlorovos, etc, may be excreted rapidly and, therefore, may perhaps be found in the urine, though not in the tissues. 

In order to reach a conclusion when and how and, and to some extent, how much of a particular insecticide was administered, the form and quantity in which the insecticide exists in different tissues and in blood and urine may give valuable clues. Indeed, an intelligent deduction is also based on the knowledge of metabolic pathways and formation of other derivatives. Thus, as parathion is excreted in the urine ultimately as p-nitro-phenol, urinary p-nitrophenol levels may indicate the extent of exposure to parathion ). In cases of mild and moderate exposure, the excreted p-nitrophenol in urine was found to be of the order of 0.057 to 0.322 mg. percent. In severe and fatal cases of poisoning by parathion, the level of p-nitrophenol in urine was from 0.16 to 1.16 mg. percent. para-Nitrophenol thus is rapidly excreted in urine and no longer detected 48 hours after the exposure to the pesticide. 

Beuers U, Pogonka T, Esterline R, et al. 1986. Inhibition of para-nitrophenol extraction by stimulation of the hepatic nerves in the perfused rat liver. Toxicol Lett 34 247-252. 

Smith LW, Hall GT, Kennedy GL. 1988. Acute and repeated dose inhalation toxicity of para-nitrophenol sodium salt in rats. Drug Chem Toxicol 11 319-327. 

If the substitution pattern is unknown or unimportant, a structure might be drawn with ambiguous positioning. For example, the following structure might imply ortho-, meta-, or para-nitrophenol, or possibly a mixture of isomers. 

The product is a mixture of ortho- and para-nitrophenol from which the ortho compound can be separated by steam distillation. A strong intramolecular hydrogen bond reduces the availability of the OH group for intermolecular hydrogen bonds so the ortho compound has a lower boiling point. The remaining pnra-nitrophenol is used in the manufacture of the painkiller paracetamol. 

This review will illustrate examples of computer projected models of inclusion complexes of structural isomers (ortho, meta, para nitrophenol), enantiomers (d- and 1- propranolol) and diastereomers [cis and trans. l(p-B-dimethylaminoethoxy-phenyl-butene), tamoxifen] in either a- or B-cyclodextrin. The use of these computer projections of the crystal structures of these complexes allows for the demonstration and prediction of the chromatographic behavior of these agents on immobilized cyclodextrin. 

P-cyclodextrin (P-CD) was supplied by Roquette Freres (France). (3-aminopropyl) trimethoxysilane (97%) (APS), tetraethyl orthosiUcate (99.999%) (TEOS) and N,N-dimethylacetamide (99%) (DMAc) were purchased from Aldrich and used without further purification. Sodium dodecylsulfate (>97%) (SDS) was obtained from Fluka. Para-nitrophenol (99%) (p-NP) was supplied by Acros Organics and lead(II) nitrate (99.99%) by Sigma. 

---